This is a homework question.     Let $f: (0, \infty) \to \mathbb{R}$ with $f(x)=\dfrac{\sin x}{x}$. I   have to prove that       $$|f^{(n)}(x)|\le \frac{1}{n+1}$$       where $f^{(n)}$ is the nth derivative of $f$.   I started to do a few derivatives:  $f^{(1)}(x)=\dfrac{1}{x^2}(x \cos x-\sin x)$  $f^{(2)}(x)=\dfrac{1}{x^3}((2-x^2) \sin x-2x\cos x)$  $f^{(3)}(x)=\dfrac{1}{x^4}(3(x^2-2) \sin x-x(x^2-6)\cos x)$  $f^{(4)}(x)=\dfrac{1}{x^5}(4x(x^2-6)\cos x + (x^4-12x^2+24)\cos x)$  I noticed that in denominator, there is always $x^{n+1}$ (because there is $x$ in denominator of $f$), but I couldn't spot a pattern for the numerator that would help me prove the inequality. Can I get a hint or a clue, please?


Help with packages in java - import does not work

I'm a C++ developer - not a java developer, but have to get this code working...  I have 2 public classes that will be used by another product.  I used the package directive in each of the java files.    package com.company.thing;  class MyClass ...   When I try to compile a test app that uses that I add   import com.company.thing.*;   The javac compiler fails with errors about com.company does not exist.  (even if I compile it in the same directory as the class files I just made a package of)  I am sure I am doing something bone-headed and silly.  I've read the  pages and tried to set up a directory structure like /com/company/thing  etc, but either I have totally screwed it all up or am missing something else.  EDIT thanks for the suggestions - I had tried the classpath previously.  It does not help.  I tried compiling   javac -classpath <parent> client.java    and the result is:  package com.company does not exist   I have the code I want to import (the two java files) in \com\company\product.  I compile those fine.  (they contain MyClass) I even made a jar file for them.  I copied the jar file up to the parent directory.  I then did (in the parent directory with the client java file)   javac -cp <jarfile> *.java   the result is:  cannot access MyClass bad class file: MyClass.class(:MyClass.class) class file contains wrong class: com.company.product.MyClass Please remove or make sure it appears in the correct subdirectory of the classpath.   EDIT  I got the client code to compile and run if I used the fully qualified name for MyClass and compiled it in the parent directory.  I am totally confused now.    compiled with no classpath set - just   javac *.java    in the parent directory - and it worked fine.  I can get a test app to compile, but that is not going to cut it when i have to integrate it into the production code.  Still looking for help.  EDIT:  Finally - not sure why it didn't work before - but I cleaned up all the files all over the directory structure and now it works.    Thanks


Direct link for PDF files in SkyDrive/OneDrive

I want to make a direct link to a document at SkyDrive, so that I'll see only the PDF at the browser, not any of the SkyDrive chrome.  For example, if you click , you will go automatically to the PDF file.  Is there any way to do this?


Recovering a lost website with no backup?

Unfortunately, our hosting provider experienced 100% data loss, so I've lost all content for two hosted blog websites:       (Yes, yes, I absolutely should have done complete offsite backups. Unfortunately, all my backups were on the server itself. So save the lecture; you're 100% absolutely right, but that doesn't help me at the moment.  Let's stay focused on the question here!)  I am beginning the slow, painful process of recovering the website from web crawler caches.  There are a few automated tools for recovering a website from internet web spider (Yahoo, Bing, Google, etc.) caches, like , but I had some bad results using this:   My IP address was quickly banned from Google for using it I get lots of 500 and 503 errors and "waiting 5 minutes…" Ultimately, I can recover the text content faster by hand   I've had much better luck by using a list of all blog posts, clicking through to the Google cache and saving each individual file as HTML. While there are a lot of blog posts, there aren't that many, and I figure I deserve some self-flagellation for not having a better backup strategy. Anyway, the important thing is that I've had good luck getting the blog post text this way, and I am definitely able to get the text of the web pages out of the Internet caches. Based on what I've done so far, I am confident I can recover all the lost blog post text and comments.  However, the images that go with each blog post are proving…more difficult.  Any general tips for recovering website pages from Internet caches, and in particular, places to recover archived images from website pages?  (And, again, please, no backup lectures. You're totally, completely, utterly right! But being right isn't solving my immediate problem… Unless you have a time machine…)


How to update Opportunity Line Item product on a related custom object?

I created Order and Order Line Item custom objects they are similar and related to Opportunity and Opportunity Line Item. When I create an Opportunity, a related Order automatically created, when I add a product to Opportunity Line Item, same product be added automatically to Order Line Item of related Order. I don't have a problem with inserting product but I can't make it update. How to achieve it? This is my code for insert but I couldnt make that product on Order Line Item update, please help me. Thanks.  trigger CreateOrderLineItem on OpportunityLineItem (after insert, before delete) { if(trigger.isInsert){      Map<Id,Product2> proMap = new Map <Id,Product2>([Select Order_line_Items__c From Product2]);     List<Order_Line_Item__c> oliList = new List<Order_Line_Item__c>();          for(OpportunityLineItem opli : [Select opportunityid, Id, pricebookentryid, unitprice, quantity From OpportunityLineItem Where id IN:Trigger.newMap.keyset()])         {                 for(Opportunity oppList : [Select id, Orders__c From Opportunity Where id=:opli.OpportunityId])                 {                                         for(PricebookEntry pbe : [Select pricebook2id, product2id, unitprice, IsActive From PricebookEntry Where Id=:opli.PricebookEntryId])                     {                         for(Pricebook2 pb2 : [Select Id  From Pricebook2 Where Id=:pbe.Pricebook2Id])                         {                         for(Product2 pro : [Select ProductCode, IsActive, Order_Line_Items__c From Product2 Where Id =: pbe.product2id])                         {                             for(Order__c orrList : [Select Id, Opportunities__c From Order__c Where Opportunities__c =:oppList.id])                             {                                 Order_Line_Item__c oli = new Order_Line_Item__c(product2__c=pro.id, Order__c=orrlist.id, UnitPrice__c=opLi.UnitPrice, Quantity__c = opli.Quantity, ProductCode__c=pro.ProductCode, id=pro.Order_Line_Items__c);                                 oliList.add(oli);                             }                         }                         }                     }                 }         }         if(oliList.size()>0)         {         insert oliList;         } }


How do I update my full list of games on my Offline PC?

So when I got Steam working offline I had 26 games listed in my library but only 2 installed. Recently I brought a bunch more so I want to update my library on my Offline PC with the full list that's on my Online Laptop.  I thought that all I would need just copy the data from userdata/[ID]/config/localconfig.vdf however when I do the number goes down to 2 (the number of games I do have installed) and also the OST I got with Monster Monpiece doesn't appear. When I restore just that file the list and the music listing returns.  So what do I need to copy over from my Online Laptop to the Offline PC to update the list of games in the library?


I have a usb powerbank(w 1.1 & 2A outputs) and I would like to power a router since I have no access to a power source. My issue is the least I've seen routers rated for are 9v min. usually 12v. Im assuming I don't need to worry about amperage because that is built into USB to self-regulate. However I'm worried about voltage. I'm wondering if there is a way around this? I've searched the internet and come up with nothing.


How to run a specific program as root without a password prompt?

I need to run something as sudo without a password, so I used visudo and added this to my sudoers file:  MYUSERNAME ALL = NOPASSWD: /path/to/my/program   Then I tried it out:  $ sudo /path/to/my/program [sudo] password for MYUSERNAME:    Why does it ask for a password? How can I run/use commands as root with a non-root user, without asking for a password?


I wish to attend my stepfather's funeral

I'm a Kenyan citizen. I have lost my stepfather, who is a British citizen. Is it possible for me to get an emergency visa to come and attend his funeral? Thank you.


Determine the minimum of $a^2 + b^2$ if $a,b\in\mathbb{R}$ are such that $x^4 + ax^3 + bx^2 + ax + 1 = 0$ has at least one real solution

I just wanted the solution, a hint or a start to the following question.  Determine the minimum of $a^2 + b^2$ if $a$ and $b$ are real numbers for which the equation $$x^4 + ax^3 + bx^2 + ax + 1 = 0$$ has at least one real solution.  Thanks in advance.


I am trying to use sequentialfs to do some feature selection in matlab. I have huge dimensional data of 22215 features. When I tried to use sequentialfs with svm as classifier so that it selects the best subset of features, it just keeps on running, probably its because of the huge number of dimensions. However, weka does the same thing very quickly. Weka has wrapper filters and it does it so quickly. What sort of heuristic does it use? Even though I tried with 5000 features in weka since it was not taking 22215 features, it gave me results quickly with wrapper filters. What should I do with sequentialfs in matlab  This is the command I am using in matlab  c = cvpartition(yS1,'k',12); opts = statset('display','iter'); [fs, history] = sequentialfs(@SVM_class_fun, X, yS1,'cv', c, 'options', opts);  SVM_class_fun  function err = SVM_class_fun(xTrain, yTrain, xTest, yTest)   model = svmtrain(xTrain, yTrain);   err = sum(svmclassify(model, xTest) ~= yTest); end   Here the dimension of X is 100x22215 where I have 100 examples each of dimension 22215.


what is the variance of a constant matrix times a random vector?

$\newcommand{\Var}{\operatorname{Var}}$In this  is claimed that if the equation of errors in OLS is given by: $$u=y - X\beta$$ Then in the presence of heteroscedasticity the variance of $u$, will not be constant, $\sigma^2 \times I$, where $I$ is an identity matrix, but: $$\Var(u\mid X)=\sigma^2\Omega$$ In order to account for the heteroskedasticity, we can estimate the transform system, such that $P$ is a transformation matrix. $$Py=PX\beta-Pu$$ Where "the variance of a constant matrix $P$ times a random vector $u$" is: $$\Var(Pu\mid X)=P\Var(u\mid X)P'=P(\sigma^2\Omega)P'$$ Can somebody explain me the proof for that?


Fully cooked ham left out for 10 hours, is it still safe to eat?

I received a fully cooked 13 pound pit ham from work at 12 noon. It was refrigerated when I got it. I made it home 4 hours later after running errands and it was 38 degrees outside and the ham was in the car the whole time. I forgot to put the ham in the refrigerator and left it still in the bag and box on the floor in the kitchen. It was 10 pm before I remembered about it and I immediately put it in the refrigerator. Is it still safe to eat?


In an incomplete inner product space, is a closed linear subspace equal to the orthogonal complement of its orthogonal complement?

It is apparently that this holds in Hilbert space, but I can not prove this for general inner product space or find a counterexample. (The only not complete inner product space known to me is $L^2$ restricted in continuous functions.)   Here give a example, but it seems don't meet the condition closeness.  By the way, Is there any other less complicated spaces equipped with inner product but not complete?


Why does Yosemite add a number to my system name and how do I stop it?

I named my system "Foob" on my 2012 MacBook Pro. Yosemite has renamed it "Foob (4)".  I wasn't sure where that "(4)" came from so I renamed it back to "Foob" in the Sharing Preferences. But, I looked today and it's now at "Foob (2)"  Why is it doing this? How can I stop it?


Algorithm to randomly generate an aesthetically-pleasing color palette

I'm looking for a simple algorithm to generate a large number of random, aesthetically pleasing colors. So no crazy neon colors, colors reminiscent of feces, etc.   I've found solutions to this problem but they rely on alternative color palettes than RGB. I would rather just use straight RGB than mapping back and forth. These other solutions also can at most generate only 32 or so pleasing random colors.   Any ideas would be great.


Batch file that inserts current date as variable to del network share files

I have a working batch file that I'm running through task scheduler to delete files with today's date in the file name.  For now I'm manually entering the date into the filename ahead of time but at least this part works.  I'm looking for the best way to have this automatically insert the variable.  I can change the naming scheme to default if it cannot be as specific as I have in this example.  For /f "tokens=2-4 delims=/ " %%a in ('date /t') do (set mydate=%%c-%%a-%%b) For /f "tokens=1-2 delims=/:" %%a in ('time /t') do (set mytime=%%a%%b) echo %mydate%_%mytime% REM 2018-07-04_1040 PM PushD "\\DISKSTATION\backups\Google Drive" && (   "forfiles.exe" /s /m "*2018-07-04*" /C "cmd /c del @path" ) & PopD


Search feature for sites on stackexchange.com

I went to  to see if a specific site existed. But with 101 sites it takes quite a while to manually scan them all, and hope you don't miss any one of them. Could we get a search box on  so that we could search for the specific sites we're looking for?


So, I have hooked up a ATtiny88, and am programming it with the Dragon AVR using ISP. I have also set up the build toolchain, using avrdude, and the gnu avr tools. Everything is working great.  Now I would like to do in-circuit debugging using the advertised debugwire which is also connected to the ISP and which the dragon supports. But which tools do I use? I see there is a avr-gdb, but it seems that I needs some kind of simulator, however I would like to debug in-circuit on the real MCU. Is this possible?  Thanks in advance.


What should do if question asker does not respond to correct answer and comment?

In StackOverFlow, sometimes question asker obviously uses comment idea, or answer solution but without giving resonse to the comment and the answer, is that responsible manner? what should we do for those kind of question asker?


Git - creating repository with gitignore

Every time I set up new project I have the same problem, but now It's time to do this right.  In my .gitignore I have paths like this: /assets/css/* /assets/images/* /assets/js/* /system/cache/* ...etc.  Now when creating and pushing to repository those paths are missing, so for example, there is no images, css, js folder in repository and when I pull the repository from other computer those files/folders are missing and the system doesn't work.  I would like to achive that those paths are on repository but it's files are ignored.   Any suggestion on how to start this repository would be more than welcome.  Cheers


How can a single Curve Interpolation Mode set to Constant?

In order to animate a character so that it grabs an object an throws it, I added a Child-Of constrained and keyframed its influence. In the F-curve Editor I can't set the curve which controls the influence to interpolation-mode Constant without changing the other curves (Which should be linear or bezier).   How can the interpolation mode of a curve changed independently?


Is it possible to break a string and store it a matrix?

Suppose i have a string ci='SKDKFJKFLKG' and I want to store it in a matrix.I am using the following code to store it in a matrix:  def chunks(l, n):      for i in range(0, len(l), n):         yield l[i:i+n] pprint.pprint(list(chunks(ci, 1)))   Output:  ['S', 'K', 'D', 'K', 'F', 'J', 'K', 'F', 'L', 'K', 'G']   What should i do if i want only 4 characters in each row of the matrix?


sudo apt-get update not working ( Ubuntu 16.04 )

I'm aware there are other similar questions asked previously but I couldn't solve the problem. I have Ubuntu 16.04.6. When I run sudo apt-get update I get the following error. Reading package lists... Done E: Failed to fetch http://iq.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-amd64/by-hash/SHA256/80072611fed265613ccc008c0d8d907243709ea50965b11609ba4909e4508617  Hash Sum mismatch E: Failed to fetch http://iq.archive.ubuntu.com/ubuntu/dists/xenial-updates/universe/binary-amd64/by-hash/SHA256/458cfcc42fea94019c8f376037a9a6692664122c63c372b80044b891d0e6235d   E: Some index files failed to download. They have been ignored, or old ones used instead.


“Firstly, secondly” vs. “Firstly, lastly” when listing just two points

Normally, if we which to illustrate our points, we can use firstly, secondly, lastly (or last but not least or finally).     There are a few pieces of information we need to notice:   Firstly,   Secondly,   Lastly,   But consider that we have only two points, are we going to use     There are a few pieces of information we need to notice:   Firstly,   Secondly,   or     There are a few pieces of information we need to notice:   Firstly,   Lastly,   It seems like firstly→secondly does not have an ending, and firstly→lastly seems to be too fast to end. Is there a better way to talk about them for when you have just two points to make?


I saw the following syntax in a bash script:   >$(command) &   I know that the ampersand & at the end makes a command run in the background, but I have never seen it in combination with the dollar sign plus the brackets around the command.  What does it do?


How to force the windows SEARCH to FIND ALL FOLDERS, containing "test" part? This is demonstration, how it is not working:  8 folders    only 7 folders    What is wrong or how to correctly input the search words? Or I have to reconfigure something?  This is "C:\Users\User\Desktop\New folder (2)" And search is inside only this folder.


I'm looking for an addon to fill faster open/broken areas with vertices

I'm looking for an addon to fill fast and simmetrically some area that needs to be closed with vertices. Doing it manually it takes a lot of time. Check the attached screenshot. thanks.     I tried to do what's explained in the duplicate question,but it didn't solved my problem. For example,I tried to select two or more edge loops with Alt + Shift + RMB and then connect them with W > Bridge,but this is what happened :    and this :    and i tried also activating the F2 addon and then pressing the F key :    none of these solutions worked for me...  errata corrige : by pressing CTRL F and then grid fill worked for me...thanks.


I often see the notation of powers of 1 in cryptography papers.  For example, let $n$ be security parameter, then what does $1^n$ mean??  From high school student perspective, powers of one is always one.... But I hope this is not. Is this a bit string of length $n$? If so why don’t they write it as $\{0,1\}^n$?


How to reinstall Ubuntu 16.04 on dual boot PC?

I have Windows 10 and Ubuntu 16.04 on my system. Windows 10 runs on SSD and Ubuntu runs on HDD.   Originally I created a 200 GB partition for Ubuntu. Now I want to format Ubuntu and install from scratch but I have important files on my HDD as well.   How can I just format that 200 GB Ubuntu partition and reinstall Ubuntu 16.04?


Biblatex 3.11: author = {{\textsc{...}}, breaks compilation

Problem statement  After my recent upgrade to TeXLive 2018 (and hence to Biblatex version 3.11), the presence of a \textsc command inside a double-braced author field of a bibliography entry causes a compilation error due to an extra } in the .bbl file  This error did not occur in previous versions of Biblatex. I am looking for a workaround to this problem, ideally without having to change a significant number of entries in my .bib file.  Minimal (non-)working example (MWE)  .tex file  Save the following to my.tex:  \documentclass{article}  \usepackage[style=authoryear]{biblatex} \addbibresource{my.bib}  \begin{document}  \cite{Foo} \printbibliography  \end{document}   .bib file  Save the following to my.bib:  @misc{Foo,         author = {{\textsc{Foo} bla}},         title = {Bla},         date = {1901}, }   Compilation and error message  Compile via  pdflatex my biber my pdflatex my   which yields the following error message:  (./my.bbl ! Extra }, or forgotten \endgroup.   Upon inspection, the offending code in the .bbl file seems to indeed feature one } too many:  [...] \name{author}{1}{}{% {{uniquename=0,uniquepart=base,hash=4e64a6262beef2c23e5c3d6f48023844}{%            family={{\textsc{Foo} bla}},            familyi={\textsc{Foo} bla}\bibinitperiod}}}% } [...]   Conditions under which error occurs  The error only occurs   If the author field is enclosed by double braces: author = {{...}}, In the presence of a \textsc{} (or \scshape) command within such an author field In Biblatex 3.11 (it did not occur before the recent upgrade)


This is my, Tom, and Alex's poster which we made for last Monday's lesson

Is this right?  How do I show ownership by the group of three of us?


I just got the error  Too many math alphabets used in version normal.   on a document I'm editing.  What can I do to fix this, other than stop using an alphabet?  All I've found online is instructions on what to do if you're using the bm.sty package, which I'm not calling (but maybe it's hidden in the AMS stuff?).  I'll note, the thing that broke it was adding mathrsfs and using \mathscr.  Anyways, as you'll see in my preamble, I tried what they suggested anyways, and it didn't work.  My preamble:  \documentclass[11pt]{amsart}   \newcommand{\bmmax}{0}   \newcommand{\hmmax}{0}   \usepackage{amsmath, amssymb, amsthm, latexsym, amscd, enumerate, MnSymbol,bbm, etex,nicefrac,mathrsfs}   I'm using   \mathbf \mathcal \mathfrak \mathscr \mathsf \mathbb \mathbbm %(for a lower case blackboard bold letter)   I recognize this is a lot of math fonts, but doesn't seem unreasonable.    EDIT: getting rid of MnSymbol fixed things...


Constructor not defined on Global Batch Class

I am receiving the following error.     Constructor not defined: [DynamicBatchApex].(String, String, Map, String) (Line: 9, Column: 30)   If you look at my DynamicBatchApex class, I clearly have the constructor outlined.  Also, what are the positives and downsides of using the global header?   global class NumberOfEmailsSchedulable implements Schedulable {       global void execute(SchedulableContext sc)        {      String query1 = 'SELECT accountId accountId, count( Id) result FROM contact WHERE accountid != null GROUP BY accountId';     Map<String, Object> field_value_pairs = new Map<String, Object>{'Number_Of_Contacts__c' => 0};     DynamicBatchApex batch1     =   new DynamicBatchApex('accountId', 'result', field_value_pairs, query1);       } }   Batch Apex Class  global class DynamicBatchApex implements Database.Batchable<AggregateResult> {  public String sObjectIdKey; public String sObjectResultKey; public Map<String, Object> sObjectFieldsToUpdate; public String query;   global DynamicBatchApex(String arIdKey, String arResultKey, Map<String, Object> field_value_pairs, String fieldName, String soqlQuery )  {       sObjectIdKey            = arIdKey;     sObjectResultKey        = arResultKey;      sObjectFieldsToUpdate   = field_value_pairs;     query                   = soqlQuery; }  global Iterable<AggregateResult> start(Database.BatchableContext BC)  {     return new BulkIterable(query); }  global void execute(Database.BatchableContext BC, List<sObject> scope)  {      DynamicSObjectUpdater sObjectUpdater = new DynamicSObjectUpdater();      for(sObject sObj: scope)     {         AggregateResult ar      = (AggregateResult)sObj;         ID sObjectId            = (ID)ar.get(sObjectIdKey);         Decimal arResult        = (Decimal)ar.get(sObjectResultKey);          sObjectUpdater.getUpdateSObject(sObjectId, sObjectFieldsToUpdate);     }      sObjectUpdater.updateSObjects();   }  global void finish(Database.BatchableContext BC)  {  } }


I have $$tan (\frac{2.05 × 10^{-4}± 2.89 × 10^{-6}}{2})=\frac{x}{667.6 × 10^6}$$   $$\therefore x = (667.6 × 10^6) \cdot tan(\frac{2.05 × 10^{-4}± 2.89 × 10^{-6}}{2})$$   I want to find $x$ with the absolute uncertainty. I don't know how to start, as I am unsure how I would propagate uncertainties with $tan$. Please include your working out when you explain the method of propagating uncertainties in this case.


Determine greatest common divisor, possibly involving the euc. algorithm

Let $m,n,k\in\mathbb{N}$ such that $n= 2k-1$ ($n$ is odd). Find $(2^m +1, 2^n -1)$, where by $(a,b)$ we mean the greatest common divisor of $a,b$.    Attempt: Let $(2^m +1, 2^n -1)=:d$, then  $$d\mid (2^m+1)\land d\mid (2^n -1)\Rightarrow d\mid (2^m + 2^n)\Leftrightarrow d\mid (2^m+2^{2k-1})$$ If $m\geq 2k-1$, that is $m=2k-1+r, r\in\mathbb{N}\cup\{0\}$, then $d\mid 2^{2k-1}(2^r+1)$ and I'm stuck. What should I do from here? How would $n$ being odd help the case?    Was told to use the euclidean algorithm here, but I don't understand what was meant by that.  References to similar problems would be appreciated.


I have a network containing 20 clients. I assigned IP range 10.0.0.1 to 10.0.0.20 to them. When I do an IP scanning I see someone using 10.0.0.131 in VMware. How can I find out which IP is this IP bridged with? i.e How can I find out which system has 2 IP? (i.e the other IP of this system)  Update:  My system IP in the network is 10.0.0.81:    Output of the IP scanner show someone using 10.0.0.131 in VMware:    And the result of tracert command show nothing between us:  C:\Users>tracert -j 10.0.0.131 10.0.0.81  Tracing route to ghasemi3.it.com [10.0.0.81] over a maximum of 30 hops:    1    <1 ms    <1 ms    <1 ms  ghasemi3.it.com [10.0.0.81]  Trace complete. C:\Users>


I use the beamer package. I want to achieve the following. Assume I have a slide of the following form (two elements):  XXX  YYY  XXX should be shown on all slides and always at the same position! YYY should be =A on the 2nd slide and =B on the 3rd slide. The problem with the existing overlay specifications is that the position of XXX depends on how much space is used by YYY. And this is different for YYY=A (2nd slide) and for YYY=B (3rd slide).


Why doesn't current flow in reverse biased diode?

Consider this reverse biased diode :     I read that no or very small current flows in reverse biased diode as depletion layers get widened and huge resistance is offered so no electrons can cross it. But, why the electrons or holes need to cross the depletion layer? In the diagram above, the positive charges (holes) are moving towards left and the current due to electrons is also in left, so won't the circuit be completed?


Let $A \in M_n(\mathbb{Q})$($n\le 2015$) such that $A^{2017}=I_n$. Prove that $A=I_n$. I think that this should be solved using the fact that the polynomial $f(x)=x^{2017}-1$ rewrites as $f(x)=(x-1)(x^{2016}+x^{2015}+...+1)$ and $x^{2016}+x^{2015}+...+1$ is irreducible, but I don't know how to proceed. EDIT: The problem linked in the comments doesn't really help me because it doesn't solve the case when $n\le 2015$.


asserted that $$k^2=\binom k2+\binom {k+1}2.$$   I checked that the formula is true. However, it intrigued me. Is there a similar expression for $k^3$? How would I find a binomial for $k^n$? This is not a duplicate question to the best of my knowledge.


Low Quality post shows as "Review completed" with all "Delete" votes, but it's not deleted?

currently shows "Review completed 21 mins ago" with one "Delete" vote and five "Recommend Deletion" votes.    However, ; how can the review be completed with all "Delete" votes, yet the answer remains undeleted?  EDIT: This was finally deleted by a moderator, but my question still stands: what's going on here?  EDIT 2:  Looks like this just  (six "Recommend Deletion" votes, but it's still around), so whatever it is, it's still going on.


What is the mathematically rigorous way to answer the question: "what is the largest fraction less than 1"? (or to explain why it cannot be answered in the manner worded).


How can I add 1 item for several files into `new` context menu in Windows 10?

When I click right mouse button in Windows Explorer I get an option to create a new Folder, Shortcut, Text Document, Microsoft Word Document etc.. I would like to add Intellij IDEA file-based project into this menu, so I can right click and rapidly create new projects in many folders. IDEA's project consist of 3 files and 1 empty folder :  src project.iml project.ipr project.iws   I have already copied these into C:\Windows\ShellNew. I've created add-ipr.reg with   Windows Registry Editor Version 5.00  [HKEY_CLASSES_ROOT\.ipr\ShellNew] "NullFile"=""   What's next?


Square matrices satisfying certain relations must have dimension divisible by $3$

I saw this tucked away in a  and am asking this question to preserve (and advertise?) it. It's a nice problem!  Problem: Suppose $A$ and $B$ are real $n\times n$ matrices with $A^2+B^2=AB$. If $AB-BA$ is invertible, prove $n$ is a multiple of $3$.


This is a javascript, I have no experience in coding unfortunately. So I need your help.   I'm trying to put a 10 sec delay on this code  document.getElementById('example').click();   The idea is that I want a link to be click after 10 secs.   I tried putting 10000); at the end of the code but it makes the code not work.  How can I make this code do what I want?


Cannot upgrade from disco 19.04 to focal 20.04 after end of life using do-release-upgrade method

At this time, I am unable to update from Disco 19.04 to Focal 20.04.  I have read several current questions that have been closed, referring to some really old questions. I have already read all the 8 year old threads and followed those instructions.  They were helpful but they don't solve my problem.  I have read all the questions suggested to me while typing this.  Please don't close my thread and refer to the old ones as they do not resolve this issue, which is NEW (as in, it has been 8 years already since those questions were answered and they don't address my problem). After trouble shooting and replacing "archive" with "old-releases" and eliminating all the third party packages from the source list, I am able to "apt update" and "apt upgrade" and the system is up to date. I have tried "full-upgrade", "dist-upgrade" and everything else I can think of.  All now say: 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.  I already fixed all the error messages I was getting using all the suggestions in all the other threads I have already read. When I run "do-release-upgrade", I get the following output: Checking for a new Ubuntu release  Your Ubuntu release is not supported anymore.  For upgrade information, please visit: http://www.ubuntu.com/releaseendoflife  Get:1 Upgrade tool signature [1,554 B] Get:2 Upgrade tool [1,337 kB] Fetched 1,338 kB in 0s (0 B/s) authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'  extracting 'focal.tar.gz' Reading cache Checking package manager Can not upgrade  An upgrade from 'disco' to 'focal' is not supported with this tool.  When I user the Software Upgrade graphical tool, I get the following: Can not upgrade: An upgrade from 'disco' to 'focal' is not supported with this tool.  This computer has many users and much software loaded and I cannot do a fresh install.  First, I don't know how to do so while saving all the users, files and programs and second, I foresee a nightmare scenario of a blown up computer with everything gone. If I can upgrade from 19.04 to 19.10, I have been unable to figure it out.  I am pretty sure it can't be done since 19.04 is no longer supported. In case it matters, my disk is encrypted. Please, please, please someone tell me there is a way to get from 19.04 to 20.04 without a fresh install, saving all my users, data and programs!  I would be absolutely shocked if there is no way to upgrade simply because I missed the update deadline.  If not, I will be forced to buy a new computer!


ssh-copy-id succeeded, but still prompt password input

I have ssh-copy-id root@c199 succeeded before.  I can login by ssh root@c199 without password prompt I want to auto login by another user ufo  (remote machine has this user) ssh-copy-id ufo@c199  ask me enter password,   /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys ufo@c199's password:  Number of key(s) added: 1  Now try logging into the machine, with:   "ssh 'ufo@c199'" and check to make sure that only the key(s) you wanted were added.  But login by ssh ufo@c199 still prompt password input .     I try to login remote centos on msys2(on Windows) by ssh , I found there are many same lines like   ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCs7RTfvn83Rxdmvgfh+F4kUlM5FzIUb9rRHaqq11xKIW1gztn/+G4tr+OWl4o6GTW2Z361hIi ugy8DPtMATN66nTTDUYO0sSvw2BrQfDY4iIENdLpkkHO8KQVGpQE+8tDkaZfD6EQLVtl0uvDE3D77tfcnBLODXgZPQsUSlssMi+pxDbSVjjKgrP hM1G/L9OTrEHKWDhF+ZBgY1RuLl7ZEdoATbhJaK4FFb9hNn/2CSibVfLts8HJGYQXIQRX/RBzaDZp47sKZvq302ewkkVorNY+c9mmoze6mi8Ip2 zEQOMi6S9zM/yRiD0XZrbmzYfNkoXA03WTmMR/DynVvX2nV /c/Users/xxxx/.ssh/id_rsa   in centos's /home/ufo/.ssh/authorized_keys ,   I have changed .ssh user's folder permissions to 700 and authorized_keys file to 644 .   Same ssh key, ssh root@c199 promptless login , but ssh ufo@c199 prompt password input ..    UPDATE  ssh ufo@c199 -vv output:  .... debug1: Server host key: ecdsa-sha2-nistp256 SHA256:zmCg5vHhBAMd5P4ei82+KsVg072KXbC63C44P0w3zbU debug1: Host 'c199' is known and matches the ECDSA host key. debug1: Found key in /c/Users/xxxxx/.ssh/known_hosts:35 debug2: set_newkeys: mode 1 debug1: rekey after 134217728 blocks debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug2: set_newkeys: mode 0 debug1: rekey after 134217728 blocks debug2: key: /c/Users/xxxxx/.ssh/id_rsa (0x60006bec0), agent debug2: key: /c/Users/xxxxx/.ssh/id_dsa (0x0) debug2: key: /c/Users/xxxxx/.ssh/id_ecdsa (0x0) debug2: key: /c/Users/xxxxx/.ssh/id_ed25519 (0x0) debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: publickey debug1: Offering RSA public key: /c/Users/xxxxx/.ssh/id_rsa debug2: we sent a publickey packet, wait for reply debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Trying private key: /c/Users/xxxxx/.ssh/id_dsa debug1: Trying private key: /c/Users/xxxxx/.ssh/id_ecdsa debug1: Trying private key: /c/Users/xxxxx/.ssh/id_ed25519 debug2: we did not send a packet, disable method debug1: Next authentication method: password


Thinking of buying a canon 550D - few questions

I'm thinking of buying a canon 550D second hand. I have a few quesitons:  1) If I buy lenses for this camera, will they work with ALL other canon DSLRs?  2) What should I look out for when buying second hand (I'm buying it from a second hand store)  3) What is this "magic lantern" program and should I get it?  Thank you


how to find a square root of a complex number?

I'm confused of what $\sqrt {3 + 4i}$ would be after I used quadratic formula to simplify $z^2 + iz - (1 + i)$


Why make new header files when you can just use C files?

I was working with sockets , and i noted that a lot of the code i wrote repeated in different programs , so i wrote functions for most of the stuff that i did and saved them in a ".c" file without a main function. I then included that file in all the programs that i wrote using #include .  I thought of creating a header file for the same just to figure out how they work but i can't figure out what difference it would make. Won't it work the same way ?


What all can you do with match in Javascript?

I'm not sure what the code below means. I know how to use match, but I'm not sure on what the brackets and "^" signs mean. Is there a website to where I can understand what all you can do with match?    var imagesURL; imagesURL = html.match(/CapImg[^"']*/g);


How can I set a custom error page for database fatal error uncaught exception

Every once in a while when I get a fatal PDO error, Drupal outputs the page without the theming and outputs the error message onto the screen. On my production site, it just outputs the page without the error message since I've disabled error reporting in php.ini. Still, I'd like that ugly looking themeless page on my prod site to be themed and informs users an error has occurred and assure them it is reported to the webmaster.   I tried creating a maintenance-page.tpl.php and maintenance-page--offline.tpl.php files and placed them in my general theme folder where all the other templates are, but it doesn't seem to get called. I also set error reporting to "none" in the admin/config/development/logging but it still outputs the error.   Any pointers would be greatly appreciated!!


"My older brother, Ted, is a good ten years older than me". Does 'good' mean 'at least or more' in this case?

Below is a paragraph in my English textbook:     Andrea - There are six of us in our family, my parents, me, the twins   and my older brother, Ted. Ted is a good ten years older than me   and the twins – they are girls – are two years younger than me. We had   a good childhood out in the countryside. My parents were always busy   with the farm and so we didn't get the help with school work and   things like that that children get today. But my parents were very   loving, especially my father. I regret not helping more around the   farm because now I realise that it must have been very hard for my   parents, especially as my grandparents lived so far away.      Source:    The  says the word 'good' in this case means     5.1 Used to emphasize that a number is at least as great as one claims.   ‘they're a good twenty years younger’   The  also gives the similar meaning:     a good three miles/ten years etc   at least three miles, ten years etc, and probably more   He’s a good ten years younger than her.   However, I feel it quite strange. Because if Ted is a person who Andrea hasn't known yet, then she can guess he is at least ten years older than her (by looking at his appearance or his photograph). In the passage above, Ted is her older brother, then Andrea must know exactly how old Ted is. He must be ten years older than her. It cannot be less than or more than 10 years (8, 9, 11 or 12 years). That's why I feel it quite strange when I understand the meaning of that sentence: '...Ted is at least and probably more ten years older than me...'  Could you kindly tell me whether I have understood that sentence correctly?


Proposed fix for: Wrong formating of the vote count in the Android app

Observation  While browsing trough the most up-voted questions in the mobile app (Stack Overflow) I noticed that questions with a vote count higher than 10.000 are displayed wrong or at least in a way I don't understand.    Expected behavior  1,1k is according to my knowledge 1100. But when opening the question it shows a vote count of 11089 which is way more than 1,1K. The correct display value would be 11k or 11,1k (with rounding).  Note that my phone locale is Dutch. Which means that points are used for separating thousands and commas decimals.  Proposed fix  Method one: decimal point when the K postfix is used and the number is shorter than 3 digits.  public static String format(int votes){     // Without K     if(votes < 10000){         return String.format("%,d", votes);     }     // K + 1 decimal     else if(votes < 100000){         return String.format("%,.1fK", votes/1000.0);     }     // Just K     return String.format("%,dK", votes/1000); }   Result:  1043    >  1.043   11089   >  11,1K   100000  >  100K   1000000 >  1.000K     Method two: no decimals at all (my favorite).  public static String format(int votes){     if(votes < 10000){         return String.format("%,d", votes);     }     return String.format("%,dK", votes/1000); }   Result:  1043    >  1.043   11089   >  11K   100000  >  100K   1000000 >  1.000K


I'm using CSV to sort the players highest sore. I have the name and scores in a list like this:  ['4', 'Score One'] ['8', 'Score Two'] ['6', 'Score Three']   Which has been created from looping through the file, finding the maximum score and making a new list with this score and the player name.   for row in reader:         highscores = ([row[-1], row[0]])   When I print (sorted(highscores)) the same list is returned to me. What I want it to sort as is:  ['8', 'Score Two'] ['6', 'Score Three'] ['4', 'Score One']   If someone could explain to me why sorted doesn't work and what I could do to fix it, that'd be great.


Let $X_i$ be i.i.d. uniform random variables in $[0,\theta]$, for some $\theta>0$ and $M_n = max(X_i)$  I am trying to find the bias of $M_n$ as an estimator of $\theta:$  $$E[M_n] - \theta = $$  Computing $E[M_n] = \frac{n}{n+1}$ I guessed the answer would be $\frac{n}{n+1} - \theta$  But this doesn't seem to be the final answer. What would be the next step? Is there another way?


Questions from SO in Russian is still on Hot Network Question list

According to this question:  entire ruSO site shouldn't become hot. But I just saw the following while searching MSE:        Direct link to the question on ruSO:   Perhaps the HNQ filter works on question title (in the current case there are no non-Latin symbols) instead of site origin. Hence, according to the post mentioned before this behaviour should be interpreted as a bug.   However, I suggest to fix such "bug" by taking another feature request in mind:


To loop through a map in c++ we do sth like this  map<string,int> mymap; map<string,int>::iterator it= mymap.begin(); while(it!=mymap.end()) {    //code here    it++; }   What if in the "code here" part i have an if statement that if evaluated to true, it erases one element from the map? How should my code change so that it still loops through all mymap elements in order?


How do you exactly create a very responsive web design? Do you create application for your website to be responsive when using mobile and/or tablets?


How do I execute if there are no non-player mobs in an area?

I am attempting to create a wave survival game, in which zombies and other mobs are fought and killed until there are none left, and another wave is started right after their deaths. I cannot figure out how to use the execute command to test whether or not zombies (non-player mobs) are in the area or are still alive to begin wave two.


I am creating a website and I have a div which sets the main (called page) and max width of the main content. How would I in CSS set another div to be 50% of the page so it will always be centred. Thanks.  Main content Div:  #page{ /* Sets page width and colour*/ margin-left: 200px; min-width: 400px; max-width: 982px; background-color: #FFFFFF; padding-bottom: 5px; }   EDIT:

   WITH CSS:   #CenterDiv {  width: 50%;  margin: 0 auto;  }


$M = \max (X,Y)$ with $X$, $Y$ independent uniform variables over $[0,1]$. Find CDF of $M$ and $E[M]$

Suppose that $X$ and $Y$ are independent uniform $[0,1]$ random variables. Find the CDF $F(x)$ for the random variable $M = \max(X,Y)$ and find $E[M]$.  So $M$ will be uniform over $[0,1]$ and is the probability of $(0 < M < k)$ the probability that $(0 < X < k) + (0 < Y < k)$? I am not even sure if I should assume these variables are discrete or continuous..  Would the cumulative distribution function be:  $0$ when $M < 0$  $2M/1$ when $0 < M < 1$  $1$ when $M \geq 1$  and would $E[M]$ simply be $E[X] = E[Y] = 1/2$?  I have a feeling something is going over my head here. Is what I am doing correct?  Thank you!


To show that $P(|X-Y| \leq 2) \leq 3P(|X-Y| \leq 1)$

I found this question while browsing through "The Probabilistic Method", by Noga Elon.  Let X and Y be 2 independent and identically distributed real valued random variables. Prove that: $$P(|X-Y| \leq 2) \leq 3P(|X-Y| \leq 1)$$  So I tried the following:  $$P\{|X-Y| \leq 2\} = P\{|X-Y| \leq 1\} + P\{X-Y \in (1,2]\cup[-2,-1)\}$$ $$= P\{|X-Y| \leq 1\} + P\{X-Y \in (1,2]\} + P\{X-Y \in [-2,-1)\}$$ $$= P\{|X-Y| \leq 1\} + 2P\{X-Y \in (1,2]\}$$ where the last step follows because $X-Y$ has a symmetric distribution. NB: A random variable Z has symmetric distribution if  $$P(Z \leq z) = P(Z \geq -z) \quad \forall z \in \mathbb{R}$$  Thus the problem boils down to showing $$P\{X-Y \in (1,2]\} \leq P(|X-Y| \leq 1)$$ and I would be done. Unfortunately, I don't know how to proceed from here. I appreciate any help, hints, useful comments etc. I receive.


Stars and bars with lower bound on individual parts

I was assigned the following problem for homework and would like to double check that I have approached it correctly.  Let $k \geq 2n$. In how many ways can we distribute $k$ sweets to $n$ children, if each child is supposed to get at least 2 of them?  This is a standard stars-and-bars problem, with the added constraint that each child gets at least two. In other words:  $x_1 + x_2 + \cdots + x_n = k$, such that $x_i \geq 2$, for $0 \leq i \leq n$  We can reduce this problem to solving over $y_i$ such that $y_i = x_i - 2$ and $y_i \geq 0$.  $\sum_{i=0}^n y_i = k$ or $\sum_{i=0}^n (x_i - 2) = k$ which reduces to  $\sum_{i=0}^n x_i = k + 2n$.  Plugging this into standard stars and bars we get $\binom{n + k + 2n - 1}{n - 1} = \binom{k + 3n - 1}{n - 1}$  Is this solution correct? Am I far off? This seems weird that the search space is bigger in the constrained version than the regular ($\geq 0$) version.


I have done a clean install of 18.04 LTS. I then installed youtube-dl using  sudo wget https://yt-dl.org/downloads/latest/youtube-dl -O /usr/local/bin/youtube-dl sudo chmod a+rx /usr/local/bin/youtube-dl   When I try to use youtube-dl, I get the following error message:  rudolffischer@HP8770w:~$ youtube-dl -U /usr/bin/env: ‘python’: No such file or directory   Python 3 seems to  be installed  rudolffischer@HP8770w:~$ python3 Python 3.6.5 (default, Apr  1 2018, 05:46:30)  [GCC 7.3.0] on linux Type "help", "copyright", "credits" or "license" for more information.   Why?


MODIS-NDVI product MOD13Q1 shows range from -1986 to 9976 but NDVI ranges from -1 to 1. What these value means? What do I need to do as corrections?  I have attached an image showing MODIS-NDVI ranges in ArcGIS.


Definition of function application in ZF-like theories

What is the definition of function application in material set theories like ZF?  I know how functions are represented using functional relations (optionally paired with the codomain).  I'm aware of the definition of function application in other formal theories such as Martin-löf theory, but there it is a a primitive notion, defined as one of the natural deduction rules. In ZF-like set theories the sets representing functions are a derived notion.  Say I had an arbitrary functional relation $f$ representing some function and a a value $x$ in the domain of $f$. How is the operation that takes $f$ and $x$ and gives me the set $f(x)$ defined using the axioms and rules of ZF+FOL?


Does each new Horcrux take half of Voldemort's remaining soul, thus taking a smaller piece each time?

When you commit a murder and create a Horcrux, you split your soul. It’s been talked a lot about Voldemort splitting his soul in 7/8 parts. But I think his remaining soul was not 1/7 or 1/8 but far more weaker than that because he did not create all Horcruxes at once.  When he created his first Horcrux, his soul was split into 50-50 (diary). But when the second Horcrux was created, it was created by Voldemort only and the first Horcrux soul should have remained intact. Hence it would have been a 25-25 split of Voldemort's main soul. And so on for every split.  Am I right?


E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable) E: Unable to lock directory /var/lib/apt/lists/ E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?


Let $f:[0,1] \rightarrow \mathbb{R}$ be a continuous function. If $f(0)=f(1)$ then exists $x\in [0,1]$ s.t. $f(x) = f(x+\frac{1}{2})$   We have that $f\left(\frac{1}{2}\right)=f(0)$ or $f\left(\frac{1}{2}\right)>f(0)$ or $f\left(\frac{1}{2}\right)<f(0)$.  If $f\left(\frac{1}{2}\right)=f(0)$ then $x = 0$ Solves the problem.  if $f\left(\frac{1}{2}\right)<f(0)$ then by the intermediate value theorem  $$\exists k \in \left[0,\frac{1}{2}\right], f(0)>f(k)>f\left(\frac{1}{2}\right) \implies$$  $$\implies f(1)>f(k)>f\left(\frac{1}{2}\right)\implies \exists t \in \left[\frac{1}{2},1\right] s.t. f(t)=f(k).$$   Now how can I show that exists at least one value of k such that $t = k+\frac{1}{2}$? (The solution is similar if $f(\frac{1}{2})>f(0)$)


I'm learning python and I'm finding python methods inconsistent.  Why is it that Len is len(s) whereas if I want to read a file I do f.read() and why do I have os.read() which is completely different that f.read().  What's the rationale of having such inconsistency in python.  Why cannot I do s.len() just like I can do f.read()? Why does os.read() exist when f.read() exists.


Why doesn't find list files in subdirectories?

I'm trying to find all the javascript files in subdirectories of my project.  The working tree is as follows:  . ├── app ├── assets ├── components ├── email.txt ├── gulpfile.js ├── node_modules └── package.json   For that end I say:  find . -name *.js   or  find . -path *.js   Strangely, first command reports only gulpfile.js, while the second one reports nothing. But I have .js files in app, components and node_modules! Why wouldn't they show up?


Proving a Relation that is a Function by Division Algorithm

Let A=B=$\mathbb{N}$  R is: (a,b)$\in$R iff for some q$\in$Integers a=5q+b WHERE 0$\leq$b<5  Given a relation, show that it's a function.  To Show:  1) $\forall$a$\in$A$\exists$b$\in$B((a,b)$\in$R)   2) $\forall$a$\in$A, there is a unique b$\in$B((a,b)$\in$R)  Proof: Let a$\in$A. Assume (a,b)$\in$R and (a,c)$\in$R where b,c$\in$B.  Do MATH  $\therefore$ b=c. QED  What math should I do to get the full proof. Thanks!


Vertically center a div in a Bootstrap Column

I've been trying yesterday to center vertically a "LinkedIn Connexion" div, with no success...  I've tried the "display: table" technique that I learned a few minutes ago but it still doesn't work... Can you help me find the issue ? I've learned Bootstrap last week and I've been having issues with all the "vertically centered" questions.    .div[title="Connexion LinkedIn"] {     display: table;     width: 100%;     table-layout: fixed; }  #linkedin-block {     display: table-cell;     vertical-align: middle;     Background-color: #eceded;     padding: 30px;     border-radius: 10px;     text-align: center; }

Connectez-vous via LinkedIn
     <a href="<%= url_for connexion_linkedin_path %>"> <%= image_tag "linkedin.png", :style => "width:50px; margin:20px" %>

     ----------- After SpaceBeers & Garrett comments ---------------------  I've tried all the suggestions, but it seams like none of them is working...  @SpaceBeers, as you can see in the photo bellow, there's an issue with your suggestions. It seams that, due to bootstrap, the line "top: 50%;" is not taken into account.   @Garrett, your help did something different, but I couldn't solve the issue yet. :S  I now think it's an issue due to Bootstrap, as it is what I'm using with :


Buck topology for a 3.3V to 1.1V for a SoC

I have been given this circuit in a design guide and it does not make sense for such a complicated circuit to be implemented just to get 1.1V out.  It requires 3.3V (input) and will give 1.1V out. The 1.1V is used to run digital functions in the chip; so I can imagine it possibly pulling too much current. Can I not use a simple voltage divider to get the 1.1V?  This image was obtained from  (page 12).  EDIT:  This is related specifically to a system-on-chip (SoC) application.   I am trying to simplify the design without losing its functionality. Is the inductor necessary and all that.


What is the LaTex command for common notation for time scale as shown in picture?


I accidentally ran this command chmod -R 755 /usr/bin on my remote server [Ubuntu 12.04.3 LTS], and I don't have the root password.  When I run sudo it gives me sudo: must be setuid root, This is the /bin folder permissions  drwsr-xr-x   2 deployer root 40960 juil. 23 11:54 bin   SSH connexion is the only access I have to my remote server.


How to separate joined objects in Blender?

I thought this would be a common question, but I can't find any answers to it past 2009 (The answers from then seem to be outdated, it tells me to do Ctrl+P but it opens up a tab called 'Set Parent To"?).  I joined three objects using Ctrl+J, how do I "un-join" these objects?  Sorry if this is a duplicate, I couldn't find any clear answers to this. Thanks!


Movie with a town where it is always night and the protagonist has amnesia

I can't remember the name of this fairly recent movie. The protagonist wakes up in a bath tub without memories. He breaks up with his wife, gets in touch with a "doctor" who claims to be able to help him, and is accused of serial killing prostitutes. The sun never seems to go up. The main plot device:       The town is in perpetual darkness. It is the experiment of a hive-mind race, that tries to understand why humans are individual. To achieve this, they move humans' memories around. They can shape the world with thought, and when the protagonist learns this power, he challenges them, destroying them. It is revealed that the Earth is long since gone, and he lives on in this false world.   I've looked for titles like City of Night and City of Darkness, but can't find it.


For vector spaces $V,W$, probe that $\Lambda (V)\otimes\Lambda (W) \cong \Lambda (V\oplus W)$.  I have tried to use the universal property, but I can not create the necessary linear transformation.


How can I make apt-get wait for another instance to finish?

Is there any way I can make apt-get wait for the other apt-get (or another package manager) process to finish?  I know that, generally, apt-get can only run one instance at a time and if we try to run another apt-get instance at the same time, then we get a message saying that some other process is using it.  My question is: how can I make apt-get wait for the other processes to finish and then run?  An advantage is that there is no need to type the command apt-get again, it will be automated after the 1st apt-get finishes.


Disable disk encryption prompt remotely ubuntu 18.04

I need to restart my machine which I do not have physical access due to COVID. I enabled disk encryption on my Ubuntu when I installed it back when things were normal. Every-time I needed to restart the machine I was in the office to enter the password to decrypt the disk. I now work from home and I do not have the luxury to go the office any time soon. Because of Nvidia driver mismatch, I need to restart my machine for that problem to go away. As you might know, I will lose my machine due to the disk password prompt which holds the machine from completing the booting process. Is there a way to disable the disk encryption password prompt remotely? I have full access from my SSH and I also have root permissions. Thanks in advance


Help me to identify a book about an alien anti-hero/spy

I'm trying to identify a Scifi/Fantasy novel book I read about 10 years ago, some time in the early to mid 2000s   I think there are more books about this setting (I think I read two) Protagonist is not human, belongs to an alien species (but looks human - I think) He has to prove himself worthy in an maze-like trial with a lot of different levels (including deadly traps and fights) There are a lot of references to these trials He has excellent combat/survival skills  He uses a "ship" to travel through dimensions, visiting other worlds/dimensions Works as a spy(?) and has a hidden agenda    Story-related    At some point he visits a machine-powered world inhibited by dwarf-like creatures  I think the dwarfs work mostly to retain functionality of their (maybe floating) world He/it rescues some inhabitants from destruction and travels with them in his ship  He/it has a conflicted personality, although he rescues some of the creatures he is not stereo-typically "good" (e.g. he doesn't prevent fights among them caused by the long journey in a small vessel).


I have installed Ubuntu 14.04 version along side with windows 7. Ubuntu freezes randomly I am unable to use any keys on keyboard since they are not working even mouse is not working.the only solution to get off from this freeze is restarting my computer.I have ATi/AMD graphic card but I removed it before installing Ubuntu 14.04.I have run memory test no problem with ram.please give some solution to get rid of this abnormal freeze. thanks in advance. system configuration  CPU=Intel core 2 duo e7500 2.93ghz  motherboard=Intel dg41wv  hard disk=Seagate 500gb  ram=4gb I dual booted windows 7 and 12.04 LTS version.in 12.04 I am getting freezes frequently so reinstalled by formatting whole computer and installing windows 7 and Ubuntu 12.04 but still freezes are frequently occurring.then I formatted whole system again installed windows 7 and Ubuntu 14.04 still I am getting random freezes..I am using GCC compiler,vim editor and Firefox no other applications


How to make persistent exposed filters in views

I'm aware of the "remember" option of views, but it is stored in session data (not persistent if you logout) and I want to keep the selections saved forever (so the users only have to do the selections once when they sign up).  I've done quite a lot of research regarding different options that maybe could do the trick, but haven't found out yet a viable solution to it. The options I've researched are:  1) With the module "views saved searches" (works but for usability reasons is not an option in this case)  2) Coding a way to remember the exposed filters selected via cookies or database (I haven't found anything about this and I don't know how to code a solution myself).  3) Making the selection in a node or profile page (with CCK, Nodereference/Entity Reference or Relation fields) and applying the selection of each user to "personalize" their view accordingly (maybe following one of the two options briefly mentioned in point 3 of this answer:  or using advanced features of relationships and/or arguments)  Any help would be appreciated.  Thanks!


If $a \cdot a = 1$ then $a = 1$ or $a = -1$

Let $F$ be a field.   And let $a \in F$ such that $a \cdot a = 1$.  Claim: $a = 1$ or $ a = -1$  Before, I begin with the proof I cannot understand what $ a = -1$ represents...  Is $a = -1$ representing the inverse of $a$?   I am capable of getting to $a = 1$ with no trouble, but how do you get the $-$ sign to show up in your proof?   Proof: This is my attempt at getting to $a=-1$.  If $a = 0$ then we have $0 \cdot 0 = 0 \neq 1$. Then this implies that $a \neq 0$ which implies that $ \exists b \in F,$ s.t. $a \cdot b = 1$, i.e. $b$ is the multiplicative inverse of $a$.  Knowing this fact prove as follows...:  $a \cdot a = 1 \implies$ $ (a \cdot a) \cdot b = 1 \cdot b \implies$ $a \cdot (a \cdot b) = 1 \cdot b \implies$ $a \cdot 1 = 1 \cdot b \implies$ $ 1 \cdot a =1 \cdot b \implies$ $a = b$.   But since $b$ is the multiplicative inverse of $a$ is this enough to say that $a = -1$?


Subset of Well-ordered set A is Order-Isomorphic to A or section of A

Claim  Let A is well-ordered set.  $C \approxeq A$ or $C \approxeq section \;of \;A$ $\forall C$ s.t. $C \subset A$   How to prove above claim?


What follows next in the sequence "unary, binary, ternary..."?

I looked on Oxford's online dictionary and was able to find the names identifying orders of a given degree:   primary secondary tertiary quaternary quinary senary septenary octonary nonary denary -- no term for 11th degree?? duodenary   I am curious as to what would be the sequence of terms regarding a set of 'n' items? I have up to four:   unary binary ternary quaternion   but I cannot seem to find anything beyond that. Does anyone know where this list may be?


Do electrical devices "take what they need"

One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them.   If a motor needs 12 volts and 500ma and I supply it with 12 volts and 3000ma will it only consume 500ma? Also, if I supply it with 15volts and 500ma what will happen?   It seems logical that an LED and a DC motor are way different when it comes to requiring/using electric where as an led has to be completely regulated and (I assume) a DC motor doesn't.   Is my understanding wrong?


I'm just beginning to study cakephp to build web applications and I have very limited knowledge at now.  I am following an example of a book, consisting of a login page to connect. I build models, controller and MySQL connection already, and now i'm with the view 'login.ctp'  This is mi code for login.ctp is just this:
Login de Usuario
 <?php echo $form->create(array('action' => 'login')); ?> <?php echo $form->input('usuario'); ?> <?php echo $form->password('pass'); ?> <?php echo $form->submit(); ?> </form>   (Also in UsuariosController I have function login())   class UsuariosController extends AppController {     var $name = "Usuarios";     var $scaffold;     var $helpers = array ('Form');     function login(){...}  }   but, when I go to localhost/cakephp/usuarios/login, show this error:  Error: Call to a member function create() on a non-object    File: C:\xampp\htdocs\cakephp\app\View\Usuarios\login.ctp    Line: 2   I don't understand this, have I to declare $form  in another side? (doesnt work either with '$this->$form->create...') I do not know what to do :/  Thank you in advance for your time.  EDIT:  from what I've read, the variable $ form can be used directly to create forms, so I say I do not understand and if I have to declare somewhere  for example () :  <?php echo $form->create(); ?>      <?php     echo $form->input('username');   //text     echo $form->input('password');   //password     echo $form->input('approved');   //day, month, year, hour, minute, meridian     echo $form->input('quote');      //textarea ?>   <?php echo $form->end('Add'); ?>


I need to write a special character similar as when you write "\aa", i.e., a with circle above, but I need the same for "u", i.e., u with a circle above, how to do it?


How to use custom function in jQuery Validation Plugin

I'm working on a custom rule (jQuery Validation Plugin), which it checks the first & last letter of string (input).  Rule : User can not enter . or _ at first or end of the input.  I have written a function with my pure javascript knowledge. I don't know how to use the function in this jQuery plugin !  My code :      var text = document.getElementById('UserName').value;     var firstChar = text.slice(0, 1);     var lastChar = text.slice(-1);      function validUser() {          if (firstChar === '.' || firstChar === '_' || lastChar === '.' || lastChar === '_') {             return true;         } else {             return false;         }      }   I have seen this link :   But still I don't know how can I use my own code.


Prove that the matrix $(I-A)$ is invertible with $ \| (I-A)^{-1} \| \le \frac{1}{1-a}$.

Suppose that $A$ is an $n \times n$ matrix with $\| A\| \le a <1$. Prove that the matrix $(I-A)$ is invertible with $$ \| (I-A)^{-1} \| \le \frac{1}{1-a}.$$ (The choice of norm does not matter)  Please help me to solve this question, I totally have no idea about


Can't remove ubuntu dock after upgrading to 18.04

I just upgrade to ubuntu to 18.04 fr0m 16.04. I was using unity launcher but when I upgrade ubuntu version it switched with dock (I assume)   Now I want to remove or hide dock. I tried s but none of them worked for me..  Have you another advice ?


How do you unfavorite a question on stackoverflow.  It seems as though once you favorite a question, then it either has the 1 in the start or the 2 in the star but not back to its original state, which is nothing in the start; or favorited.  Thanks!


A world where nothing can be hidden. No lies, always truth

In a Bollywood movie Pk, a man comes from a planet where lying is not possible as all the thoughts/knowledge is transferable via human contact. Due to which they do not have to lie about anything or hide anything from each other.  Say, such a society plausible with technology, if we decide to abandon the privacy as we know today. All the recorded data (written, spoken, recorded videos etc.) and thought (via neuralink) is accessible to everyone, everywhere.  Basic idea behind the question is, people worry about data being accumulated at one place (entity or government) and being used against them or to deceive them. If everything is accessible/known to everyone of about anyone and anything, what does privacy mean in this case?


Let $A$ be an $n \times n$ complex matrix and $V = \{B\mid AB=BA\}$.  I've proved that $V$ is a vector space. How can I prove that $\dim V \ge n$ for any $A$?


Cross product of compact spaces is compact

Let $(X, \rho)$ be a compact metric space. Prove that $X \times X$ is compact in the product topology.  I am thinking that you need to construct an open cover of $X$, then obtain the finite subcover that follows from the compactness of $X$. Then somehow use the cross product of the open cover to make a finite subcover subcover of $X \times X$.  I am just not sure exactly how notation etc should go.  Thank you!


Creating a world map centered on another meridian in QGIS

I am trying to create a world map, but centered over the Pacific rather than the Prime Meridian. Recentering the projection (standard Mercator) on 180 degrees gives me a lot of ugly artifacts where countries are stretched across the "cut line" of the map.  I assume I need to do some kind of intentional clipping (like clipping to hemisphere with an orthographic projection), but I'm not sure how properly to make QGIS cut everything cleanly on a meridian. Is there a standard way of doing this? A plugin?  (I am using the Natural Earth 50m countries shapefile.)


Trying to update a Dell laptop from Ubuntu 14.04 to 20.04

So I've been trying to update the computer for some time, and I can't didn't the answer of how to do it. I've got a Dell Inspiron 3558 and it's running Ubuntu 14.04. I want to update it to the 20.04 ver. It's my completely first time using any kind of Linux software so I don't really have much idea of what I'm doing. I've tried the Software updater, but it prompts me to a window something like: „Failed to download repository information Check your Internet connection.“ I've tried to update it via the Terminal, haven't got much luck with it aswell.


What does [:] mean in the context of "for nm in namesList[:]:"

I'm currently learning Python, and I struggle to understand what the slicing [:] does in the for loop shown below.  I failed to find any questions about the [:] syntax, so I am posting a question.  I understand that writing namesList[2:] would slice the list from index 2: ['three', 'four', 'five']  And namesList[:2] would slice the list until index 1: ['one', 'two'].    If in the for loop I only put for nm in namesList: it is stuck on an infinite loop, constantly inserting 'four' to index 0. Why is it stuck?  From what I can see in debugging, in the for loop with namesList[:], it continues from where it stopped. But why namesList: doesn't continue, and namesList[:] does? How does [:] work, what does the syntax mean?    names = "one two three four five" namesList = names.split()     for nm in namesList[:]:     if nm[0] == "f":         namesList.insert(0, nm) print(namesList)  # Output: ['five', 'four', 'one', 'two', 'three', 'four', 'five']   names = "one two three four five" namesList = names.split()     for nm in namesList:     if nm[0] == "f":         namesList.insert(0, nm) print(namesList)  # Infinite loop


replace column of a csv file with column from another file

I have two sample files like this:  $ cat file1 abc,sachin cat,kumar   $ cat file2 xyz pressure  $ cat file3  xyz,sachin pressure, kumar    I want the first column of file1 to be replaced with file2.  I tried doing something like this:  $ awk 'FNR==NR{a[NR]=$3;next}{$2=a[FNR]}1' file1 file2   I'm using Solaris 10 and it didn't appear to support this. Any other suggestions?


Show that $L^p(U) \subseteq L^q(U)$ for $p > q \geq1$.

Let $U \in \mathbb{R^n}$ be a closed space and $p > q \geq1$. Show that $L^p(U) \subseteq L^q(U)$.   I need some hint to start with this!


Err:1  focal/main i386 libglu1-mesa i386 9.0.1-1build1 404  Not Found [IP: 64:ff9b::673a:6712 80] E: Failed to fetch   404  Not Found [IP: 64:ff9b::673a:6712 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?


Is it possible to strace the builtin commands to Bash?

Inspired by this question, titled: , while attempting to answer this I tried the following command and was a bit surprised that I couldn't run it:  $ strace cd $HOME   Is there a method I can make use of to run strace for the builtin commands to Bash?


How to run a fresh version of AIX in a Virtual Machine with a Linux host?

I need to learn about , and I only have a laptop with Fedora 14/VirtualBox on it. Is there any chance that I could run an AIX guest in my VirtualBox?   My laptop has an Intel(R) Core(TM)2 Duo CPU T7100 @ 1.80GHz, and I read that it only runs on RISC architecture. So there's no way I can run it on my laptop?


Can you see who all favorited your question?

When someone marks your question on SO as a favorite, you get to see a star and the number of users that marked the question as their favorite. Is there a way to see who all marked it as a favorite?  If not, it would be a nice feature for SO to have.


What is the difference between "what" and "which" in this context?

If I want to ask my teacher the exercise we are at which of the following sentences should I use?     1 "which exercise are we at?"      2 "what exercise are we in?"


I try to do the configuration again but i coudl not do it     Now I see my Services Stopped bu I can't start again because in Action is not possible  I'm trying to open a page but I'm getting the next error:     An unexpected error has occurred.   Troubleshoot issues with Microsoft   SharePoint Foundation.   Correlation ID:   8005fa8b-6fc9-4a11-9ecb-9e8fba160035  Date and Time: 11/6/2013   12:07:01 PM   I couldn't open any page and I really don't know why. I can only open SharePoint 2010 Central Administration, that is all. I confirmed the event viewer and I only find the next message but I don't know if this is the root cause of the trouble.     "There are no instances of the User Profile Service started on any   server in this farm. Ensure that at least one instance is started on   an application server in the farm using the Services on Server page in   Central Administration."   Edit:  Central Administration : Services on Server: SERVER   The Microsoft SharePoint Foundation Database Status = Started   [EXTRA COMMENT] I don’t know the root cause of the trouble I only did a copy of the server (Virtual Server) but I don´t know if this action generated the problem and the lost setting


If I zoom to far out everything dissapears

If I zoom out too far, all objects disappear, how can I adjust this so that I can see them from further away, so that the view is simply bigger?  Thx for our help


Can I use the same board for meat and vegetables?

I've heard that it's not good to use the same board for vegetables and meat, not only when you are making a salad but in general. Something about the bacteria in dirt and the bacteria in the meat is a bad mix.  But I'm wondering if you are making a stew of some sort, where you need to boil both meat and vegetables together, can I safely use the same board for both?   I'm thinking since it will be cooked together anyways, what danger can there be?


complete metric space $X$ and nested sequence of closed sets $A_m \subset X$ where $\bigcap_{n=1}^\infty = \emptyset$

What is an example of a complete metric space $X$ and a nested sequence of closed sets $A_m \subset X$ such that $\bigcap_{n=1}^\infty A_m = \emptyset$? My analysis professor mentioned this in office hours as something interesting to think about, and I've thought about it for a while. But I haven't made much progress...


Question Regarding Number Theory(Congruence Modulo specifically).

Consider the Group U(55) under multiplication modulo 55. Let x∈U(55) be such that x.x=26 and x>30. Then find the value of x.   Now I want to know that if the above question can be represented in congruence equation. If yes then please tell me how it would be done and recommend a book or something from which I can learn and practice such questions.


How was the Triwizard Tournament supposed to be entertaining for the audience?

As has been established in another question, although the four champions had to face really difficult challenges,    The first task makes the most sense to me. It seems to be quite entertaining for the audience. They could see the fights of the champions with their dragons but the second task had the audience watching the Black Lake for one full hour. Since Dumbledore had to question one of the merpeople about what happened, I don't believe that anybody was able to witness anything except when each of the champions reappeared on the surface.   The same goes for the third task. The audience watched the walls of the maze for the most time. Mrs Weasley and Bill came to the castle specially to watch the third task, but I don't think that there was anything interesting to watch at all.   So, if no-one could see anything, in what way was the Triwizard Tournament meant to be entertaining for the audience?


How does negation affect the use and understanding of "or" and "and"

I'm trying to make more sense of how negation effects how a sentence is parsed and understood if and's and or's are used within them.  Pop quiz: You are trapped on a bus with a bomb going 50 MPH. You have a radio... (okay enough Keanu Reeves references) :-)  Let's say the bomb expert says "Don't cut the red or green wires." I think that means "Do not cut the wires colored red. Do not cut the wires colored green."  Now, let's say the bomb expert said on the radio "Do not cut the red and green wires", instead. Do I take that to mean:     "Do not cut the wires colored red. Do not cut the wires colored green."   OR     "Do not cut the wires whose insulation has red and green stripes." ?   OR     "It's okay to cut the wires colored red or the wires colored green, as long I don't cut one of each color."   Which meaning should I take if the radio breaks and I can't ask follow up questions?


I know that one way to find the number of divisors is to find the prime factors of that number and add one to all of the powers and then multiply them together so for example  $$555 = 3^1 \cdot 5^1 \cdot 37^1$$  therefore the number of divisors = $(1+1)(1+1)(1+1) = 2 \cdot 2 \cdot 2 = 8$  What I do not know (and can't seem to find when I look) is WHY this relationship exists or a formula which shows its proof.  Has anyone seen such a formula?


How can I make the trackpad (not mouse) significantly faster?

Context  I run a three screen setup and it takes forever to get from side to side when using the trackpad even when set to max in settings. I'm looking for (and thought I had found) a solution that will allow me to set the trackpad tracking speed as arbitrarily high as I want.  What I've Done So Far  I've already tried the solution laid out . The problem is that no matter how high I set the number when running defaults write -g com.apple.trackpad.scaling x the sensitivity still isn't high enough for me.  At first I thought this might mean that there is another limit imposed besides the one dictated by the GUI. Proceeding on this hypothesis (and the assumption that if Apple throttled the trackpad they would do the same to the mouse) I ran defaults write -g com.apple.mouse.scaling 1000 (note the 'mouse' instead of 'trackpad').  Result: My mouse is now so sensitive that if my cursor happens to land where I intend I can only ascribe it to the will of God.  Remaining Problem  No matter how high I set the number for the trackpad, one motion across its surface isn't enough to get from the left edge of my first monitor to the right edge of my third. Note: The goal here is not to set the trackpad speed and mouse speed separately (as in the question marked as duplicate). I simply wanted to indicate that the analogous steps that work for a mouse do not work for a trackpad. In addition, the selected answer in the duplicate provides a dead link (so not much help).   The goal is to be able to set the trackpad speed significantly faster than allowed by the GUI in settings. I'm open to downloading a third party tool, but would prefer a command line solution (or explanation as to why the one I've tried doesn't work as expected).  I realize this is probably a pretty niche question, but your help is much appreciated.


As many videos are telling about the future when batteries would be exchanged by , which would charge fast and with larger power density. How much amount of these capacitors with what specifics would be needed for this?


Cannot run basic commands in the terminal since Ubuntu crash

I am using Ubuntu with Ubuntu 64-bit -VMware Workstation 15 Player. A few days ago, while I was running Ubuntu, I had to log out of my windows user due to an error, which led to a crash (everything froze) in the virtual machine. I 'fixed' that by clicking on the pause sign (top left corner of the added pictures) and restarted the machine, now it is running again. But ever since I cannot use commands such as 'll' anymore.   I noticed the change in the terminal, which usually had my hostname in the headline and the name itself highlighted in every line, so I created a new sudo user (those commands work) for test purposes and when l switch the user to it, it looks the way it did before just, so I assume I accidentally changed something concerning my old user I cannot undo myself.  Those are the differences in appearance:     Besides, merry christmas ( : .


Creating a Math library using Generics in C#

Is there any feasible way of using generics to create a Math library that does not depend on the base type chosen to store data?  In other words, let's assume I want to write a Fraction class. The fraction can be represented by two ints or two doubles or whatnot. The important thing is that the basic four arithmetic operations are well defined. So, I would like to be able to write Fraction<int> frac = new Fraction<int>(1,2) and/or Fraction<double> frac = new Fraction<double>(0.1, 1.0).  Unfortunately there is no interface representing the four basic operations (+,-,*,/). Has anybody found a workable, feasible way of implementing this?


Can we use LinkedList even though there is risk of memory overhead. In that isnt using ArrayList better option

I know that when it comes to search operation ArrayList is better. And when it comes to insertion and deletion operation LinkedList is better. But I have read that linked list will cause memory overhead. In that case is it still safe to use LinkedList. Is so in what situation we have to avoid using LinkedList even though our logic contains more of insertion and deletion operation


Intuitively, it seems to me that $|\mathbb{R}^{2}| > |\mathbb{R}|$. My intuition says something to the effect of: There exists a bijection between $\mathbb{R}$ and $\{(x,0) : x \in \mathbb{R}\}$, and the second set is a subset of $\mathbb{R}^{2}$.  But I remember reading somewhere that $|\mathbb{R}^{2}| > |\mathbb{R}|$ is not true, though I may be mistaken.  I know only the very basics about countable sets which are infinite. I also know that $\mathbb{R}$ is uncountable.  To be clear, I am looking for:   Is $|\mathbb{R}^{2}| > |\mathbb{R}|$? Why? Any quick resource/lecture notes to quickly brush up on related concepts.   The most relevant question I could find was:


Why are figures 1-9 written as numbers, but after 9 written in alphabet form?

I have tried to research this .. could anyone answer why figures 1-9 are written as digits/numbers and then from 9 onwards they are typed in alphabetical form?


Concatenate multiple strings versus String.Format

Here is 2 methods which result the same:  public class MessageManager {     public void SendMessage(string name, int count)     {         string message = "Hi " + name + ". I know you don't like cake, so I bought you " + count + " lollipops. Same thing, right?"; // No boxing. "count" was converted to string somehow.         //Console.WriteLine(message);     }     public void SendMessage2(string name, int count)     {         string message = String.Format("Hi {0}. I know you don't like cake, so I bought you {1} lollipops. Same thing, right?", name, count); // Boxing "name" and "count" + executing unnecessary code.         //Console.WriteLine(message);     } }   So I guess the second method will be slower then first because of boxing and executing some additional code which inside String.Format() method.  I have tested them with following method:  public static class PerformanceTester {     public static TimeSpan TestAction(Action<string, int> action)     {         Stopwatch timer = new Stopwatch();         timer.Start();         for (ushort i = 0; i < ushort.MaxValue; i++)             action("Alex", 1000);         timer.Stop();         return timer.Elapsed;     } }   And here is the usage of it:      static void Main(string[] args)     {         MessageManager mm = new MessageManager();          TimeSpan ts_m1 = PerformanceTester.TestAction(new Action<string, int>(mm.SendMessage));         TimeSpan ts_m2 = PerformanceTester.TestAction(new Action<string, int>(mm.SendMessage2));          Console.WriteLine("First message took time: " + ts_m1.ToString());         Console.WriteLine("Second message took time: " + ts_m2.ToString());          Console.ReadKey();     }   Output with my Intel® Core™2 Duo Processor E8200 (DEBUG):    Output with my Intel® Core™2 Duo Processor E8200 (RELEASE):   I saw String.Format used almost everywhere (guides, blogs, tutorials etc.) but it is actually slower than simple string concatenation. I know when I talk about C# I must not care about performance, but the results in this example is too awesome. The question is: "Is there any best practice where String.Format is actually better than concatenation of strings."


I would like to try and create my own audio dataset which I can then use to train machine learning models for classification. The data that I've gathered consists of multiple long audio files of around 1 hour each, containing audio of different categories. Since this is my first time working with audio files instead of data in a tabular format, I am a bit lost on how the do the labeling/preparation.  Most information I find on the internet is mainly related to applying machine learning models to existing pre-labeled datasets. I am hoping to find some more information specifically about what would be the best way to approach the labeling and, if possible, also some information regarding the division of the long audio files into much shorter audio snippets.


WebException not being caught by catch statement

try {     this.Invoke((MethodInvoker)delegate     {         Uri uri = new Uri("mywebpage.com");         NetworkCredential credentials = new NetworkCredential("username", "password");         byte[] lnBuffer;         byte[] lnFile;         HttpWebRequest lxRequest = (HttpWebRequest)WebRequest.Create(uri);         lxRequest.Credentials = credentials;         // the line below throws a webexception that for some reason is not being caught by my webexception catch statement.         using (HttpWebResponse lxResponse = (HttpWebResponse)lxRequest.GetResponse())         {             using (BinaryReader lxBR = new BinaryReader(lxResponse.GetResponseStream()))             {                 using (MemoryStream lxMS = new MemoryStream())                 {                     lnBuffer = lxBR.ReadBytes(1024);                     while (lnBuffer.Length > 0)                     {                         lxMS.Write(lnBuffer, 0, lnBuffer.Length);                         lnBuffer = lxBR.ReadBytes(1024);                     }                     lnFile = new byte[(int)lxMS.Length];                     lxMS.Position = 0;                     lxMS.Read(lnFile, 0, lnFile.Length);                     lxMS.Close();                     lxBR.Close();                 }             }             lxResponse.Close();         }          using (MemoryStream lxFS = new MemoryStream(lnFile))         {             lxFS.Write(lnFile, 0, lnFile.Length);             lxFS.Position = 0;             Image resizedimage = new Bitmap(Image.FromStream(lxFS), new Size(320, 240));             pictureBox23.Image = resizedimage;              //otherform.picboximage = Image.FromStream(lxFS);             lxFS.Close();         }     }); } catch (WebException e) {     this.Close(); } catch (InvalidOperationException e) {     this.Close(); }   the line with the comment above it throws a web exception however my catch statement for webexceptions is not catching it.  Any ideas? Thanks


The other day I was reading Topics in Algebra by I.N.Herstein and found a problem which can be summarised as -  Show that any two non-abelian groups of order $pq$ where $p$ and $q$ are distinct primes with $p>q$, are isomorphic.  My strategy there exists a subgroup of order $p$ and $q$ out of which the $p$-group is a normal group by using the fact that  there exists a homomorphism $\alpha:G\to S_q$ such that the kernel is contained in the $p$-group.  As $p$ and $q$ are cyclic let their generator be $a$ and $b$ respectively. As $\langle a\rangle \cap\langle b\rangle=\phi$ then $\forall g\in G$ $g=a^ib^j$. As $\langle a\rangle $ is normal $bab^{-1}=a^k \implies b^iab^{-i}=a^{k^i} \implies k^q \equiv 1\pmod{p})$ , $k\neq1 $ as it is non-abelian group. Let the two groups be $G_1$ and $G_2$. Let $a_1$ and $b_1$ are the generators of $p$-group and $q$-group respectively and similarly $a_2$ and $b_2$ for $G_2$. Let $$b_1a_1b_1^{-1}=a_1^{k_1}$$ $$b_2a_2b_2^{-1}=a_2^{k_2}$$ If I use the fact that $\Bbb Z_p$ multiplicative group is cyclic, then there exists $n\in N$ $,n\le q-1$ such  that $[k_2]^n=[k_1] $ and  $[k_1],[k_2] \in \Bbb Z_p$. hence $\beta :G_1 \to G_2$ , $\beta(a_1)=a_2$ and $\beta(b_1)=b_2^n$ is an isomorphism. But the fact that $\Bbb Z_p$ multiplicative group is cyclic is not done in the previous parts. So, I am asking for a proof without using the fact that $\Bbb Z_p$ multiplicative group is cyclic.


Why is Ubuntu 15.04 End Of Life Jan 2016

I just got Ubuntu 15.04 running well, still customizing of course.  Why is there an End Of Life so soon, Jan 2016?  There are many things still being worked out how can it end that quick?


Reading a file with spaces and brackets in the name -CLI

I would like to know if you have a file name >  abc (1).bin or > abc (1).txt files, how do you read them. The files are with the space and bracket before the .bin or .txt extension.  To read the .bin file I have a tool, I can read it easily if I remove the "space and (1)" from the filename. But when I have this space and bracket (1).bin name, I can not read it.  When I cat a .txt file, it works.. but it doesn't work with the .bin file. Below are the requested tests:  $ cat full_logs-10.2.0.103-2018.02.07\ \(1\).txt  hello, this is a test.  --------xxxxxxx------xxxxxxx------------xxxxxxx--------  $ LogAnalyzeRebirth -p -x ./ full_logs-2018.02.07\ \(1\).bin  usage: LogAnalyzeRebirth [-h] [-A] [-B] [-C] [-D] [-E] [-F]                          [-G GRAPH [GRAPH ...]] [-H] [-I [HISTOGRAM]] [-L]                          [-M] [-N] [-P [PDF]] [-R] [-S] [-T] [-U] [-V] [-b]                          [-c] [-e] [--moo] [-f] [-g] [-i] [-k] [-l] [-m] [-n]                          [-o] [-p PATH] [-q] [-r] [-s] [-t] [-v] [-x EXTRACT]                          [-z] LogAnalyzeRebirth: error: argument -p/--path: expected 1 argument(s)  --------xxxxxxx------xxxxxxx------------xxxxxxx--------  $ LogAnalyzeRebirth.py -p ./ -x "full_logs-10.2.0.103-2018.02.07 (1).bin"   (\ /)                      (\ /) ( . .)      LogAnalyzeRebirth     (. . ) c(")(")                  (")(")o  sh: 1: Syntax error: "(" unexpected sh: 1: Syntax error: "(" unexpected sh: 1: Syntax error: "(" unexpected Extract failed. LogAnalyzeRebirth can't find full_logs-10.2.0.103-2018.02.07 (1).bin No such file or directory : ./full_logs-10.2.0.103-2018.02.07 (1)/dmesg  ---   Firmware_version   ---  No such file or directory : ./full_logs-10.2.0.103-2018.02.07 (1)/version.txt  --------xxxxxxx------xxxxxxx------------xxxxxxx--------


Logistic regression in R resulted in perfect separation (Hauck-Donner phenomenon). Now what?

I'm trying to predict a binary outcome using 50 continuous explanatory variables (the range of most of the variables is $-\infty$ to $\infty$). My data set has almost 24,000 rows. When I run glm in R, I get:  Warning messages:   1: glm.fit: algorithm did not converge   2: glm.fit: fitted probabilities numerically 0 or 1 occurred    I've read the other responses that suggest perfect separation might be occurring, but I'm confident that isn't the case in my data (though quasi-complete separation could exist; how can I test to see if that's the case?). If I remove some variables, the "did not converge" error might go away. But that's not always what happens.  I tried using the same variables in a bayesglm function and got the same errors.  What steps would you take to figure out exactly what's going on here? How do you figure out which variables are causing the problems?


I have just come across Liskov Substitution Principle and casting during a lecture of (Java) Object-Oriented Programming. I understand what the principle states, that is, I can initialise a subclass with the type of a superclass:  SuperClass superClass = new SubClass();   My first concern regards the purpose of such operation. Why can't I just declare the subclass as usual (example follows)?  SubClass subClass = new SubClass();   Right after this, I got stuck on casting, as follows:  SuperClass superClass = new SubClass(); SubClass subClass = (SubClass)superClass;   Again, I struggle understanding the point of all of this.   Can anyone provide any clarification on the purpose of these procedures?


Problems printing OpenLayers Plugin Maps To Scale

In the print composer I can print all maps to scale and satisfactory. However, when I add the OpenLayers, usually Bing Aerial, to the project I cannot print it out to scale. I click the scale box, set it to the relevant scale.   The image below is a section of the actual size with OS mapping:    The next image is with the OpenLayers.    Both images cropped to remove client info. It is almost double the size but in-between scales. Is there any way to correct this?  Using Windows 7, QGIS 1.8.0.


Number of Elements Not divisble by 3 or 5 or 7

if A={1,2,...,600} includes all natural numbers between 1 to 600. I want to find number of elements of A that not divisible by 3 or 5 or 7?  any hint or idea?


i want to make a good design for products, services and offers in a mobile application and i need users opinions about this, So i am asking what is the best for usability a "5-Start" rating or a "Like"?


What's amazing about these open world games is the freedom I have as a player. If I don't want to follow the main story line for a while, and just explore, I can do that, and the game won't break.  On the other hand I don't particularly like the feeling of having made a significant, bad choice in the game, among the lines of Yeah, that dialog option you selected hours ago? This amazing quest line is now off limits.  If I recall correctly, in Morrowind, I had to progress through a few different guilds' quests in the right order, otherwise it'd have stopped my progress in a few guilds.  As a Skyrim example, it doesn't appear that the very first choice made in Helgen at the very beginning has much significance. If someone told me It's not that significant, you still get to choose sides (or, rather not told me "This is important"), that'd help.  Another example: Based on a question I read here, I should probably make sure that I don't throw away any of the dragon priest masks and need to make sure to collect one during a specific quest. This would be relevant for this topic if I could easily miss it otherwise while doing that question.  This includes accidental problems possibly caused by bugs: It appears .  It doesn't matter too much which of the love triangle guys in Riverwood I support: That's not nearly significant enough.    Are there non-obvious, hidden decision points in the quests and story lines? When playing in a certain area, doing a certain quest, what do I need to make sure to do or not do, to not accidentally prevent me from getting or achieving something significant?  I still want to explore on my own, but want to be aware of which choices are important.  This is somewhat related to .


Where I live, there are hardly any beggars. But wherever I travel (big cities, small cities -- really anywhere) I keep occasionally running into beggars. Now, I do sympathise with these people, but I still feel terribly uncomfortable when I'm approached by one.   What is the best way to "get rid" of a beggar without being outright disrespectful to them? Often I just awkwardly ignore them or tell them I don't have any money with me, but sometimes they are way more persistent than what I'm comfortable with.


If $g \circ f$ is injective, so is $g$   I don't think this is true. I think that $f$ has to be surjective.  So I am going to try to prove that:     If $g \circ f$ is injective, and $f$ is surjective, then $g$ is injective.   First off, $g \circ f$ means that $(g \circ f)(a) = (g \circ f)(b)$ then $a=b$.  And $f$ being surjective means that $\forall b \in B, \exists a\in A$ such that $f(a)=b$  Proof  Suppose that $g$ was not injective.  $g(f(a))= g(f'(a))$ and $f(a)\ne f'(a)$  But $g(f(a)) = g(f(b)) \to a=b$ $g(f(a))= g(f(b)) \to f(a)=f(b) \to a=b$ Hence contradiction, since $g$ is not injective.  So $g$ is injective.  Is this an acceptable proof, I think my logic is iffy around the second last paragraph.


SMTP 25 closed even though I allow everything in firewall (Debian server running sendmail)

I am running sendmail + dovecot in my Debian server. I have enabled the firewall rules to allow everything:   iptables -P INPUT ACCEPT   iptables -P OUTPUT ACCEPT   iptables -P FORWARD ACCEPT   iptables -F   iptables -X  However after a quick check at yougetsignal.com, my port 25 is still being blocked. But 143, 80 are okay.


"not constructive" topics are sometimes the best SO topics

When I google for an answer, and one of the top hits is a stack overflow topic, it almost always (>90%) has been closed as being "non-constructive".  I know there is a policy against topics that lead to debates, but my observation indicates that there must be value to aggregating "debates".  When studying a new aspect of programming, these debates can quickly catch someone up on major views and pros/cons, even when there is no definite answer (which is also useful information!!! scientist speaking here).  Has there been any testing to see if there is actually any significant downside to keeping these open?  Especially if there has been a large number of incoming referrals (like from Google) to certain topics?  Update: A common trigger is when looking for a good tool(s) to do a job.  SO topics often come up in these types of searches and are hugely helpful... which is sort of funny when you notice it's been closed... then you wonder if the information is no longer up-to-date.


Find $\alpha$ such that the given field is $\mathbb{Q}(\alpha)$

This question is in regards to separable field extensions. I am to show that this $\alpha$ is in the given field and verify by direct computation that the given generators for the extension of $\mathbb{Q}$ can indeed by expressed as formal polynomials in $\alpha$ with coefficient in $\mathbb{Q}$.   For $\mathbb{Q}(\sqrt2, \sqrt3)$, the given answer is as follows :  "We try $\alpha = \sqrt2 + \sqrt3$. Squaring and cubing, we find $\alpha^2 = 5 + 2\sqrt2\sqrt3$ and $\alpha^3 = 11\sqrt2 + 9\sqrt3$.  Because $\sqrt2 = \frac{\alpha^3 - 9\alpha}{2}$ and $\sqrt3 = \frac{11\alpha - 9\alpha^3}{2}$, we see that $\mathbb{Q}(\sqrt2 + \sqrt3)$ = $\mathbb{Q}(\sqrt2, \sqrt3)$"  I'm trying to understand the logical jump from knowing the $\alpha^2$ and $\alpha^3$ to the value of $\sqrt2 = \frac{\alpha^3 - 9\alpha}{2}$ and $\sqrt3 = \frac{11\alpha - 9\alpha^3}{2}$. Also, how is this relevant to the question and separable fields?   Thank you in advance.  (It isn't a duplicate, I believe. I'm trying to draw a connection between $\alpha^2$ and why $\alpha^3$ was even used in the first place when the the irreducible is of degree 2.)


Safely moving and creating new tempdb files

Two things I'd like to know:   how do you safely move tempdb with minimal downtime? how many tempdb files do you need?   Is it 1 file per core? So quad-core = 4 tempdb files, creating three new ones?


I know that NULL check for every arguments in a public API is good practice in java. But just curious, do we need do such NULL check in the front of all methods. There are definitely values for doing this: catching error earlier and providing better error message. But is it worthy, I mean doing the same NULL check in all methods seems too tedious. If that is needed, why JVM cannot the job by default.  Please share your thoughts.


Nonparametric Correlation with Dichotomous Variable

I have a continuous variable (total cholesterol mg/dl) and a dichotomous variable (gender). I want to see whether a relationship exists between the total cholesterol level and gender.   The data is non-normal and the assumptions for point-biserial correlation are violated. Is it appropriate to use a Spearman's Rho or a Kendall's Tau when one variable is dichotomous?


How many primary partitions can be created on a computer running Windows 8?

I remember reading somewhere that as opposed to the former versions of Windows - more than 4 can be created, but I can't seem to find it on the web now. Is this true?