Solving "MySQL server has gone away", mysql error 2006

I have a site at hostgator, using their "Business account". It's cheap, and comes with a private SSL cert. HOWEVER, their MySQL settings are such that any db connection goes stale fairly quickly, and then the hostgator staff try to convince you to use a VPS or dedicated server at multiple times the expense.  I'm creating and deploying WebAPIs, which can have a 'conversation' which exceeds 60 seconds. When this occurs, the db connection handle is stale, causing any db operations after my timeout to fail.  I'm in the process of implementing the following solution, but am curious if anyone else has solved this issue (where they can not modify their my.ini or my.cnf to give MySQL more resources) in a similar or completely different manner.  last part of a hook_update:  $ret = db_query( "UPDATE {my_table} set field1 = '%s', field2 = %d ... WHERE vid - %d", $node->field1, $node->field2, ... $node->vid ); if (!$ret) {        // get private storage directory for this node:        $cexStorage    = _cex_front_getCexStore();        $nodeFilesPath = DRUPALROOT.'/'.$cexStorage.'/'.$node->storeDir;        $fname         = $nodeFilesPath.'/recover.node';         $readyToWrite  = serialize( $node );        file_put_contents( $fname, $readyToWrite );        if (file_exists( $fname )) {          _dbgReport( 'seems to have worked!' );        }     }   Then this is called in my hook_form, right after I determine that node->nid is valid:  function _cex_front_recover_node( &$node ) {   if (!isset($node->storeDir)) {      _dbgReport( '**************************** _cex_front_recover_node: no storeDir!!!' );      return;   }    // get private storage directory for this node:   $cexStorage    = _cex_front_getCexStore();   $nodeFilesPath = DRUPALROOT.'/'.$cexStorage.'/'.$node->storeDir;   $fname         = $nodeFilesPath.'/recover.node';   if (file_exists( $fname )) {     $recovered = file_get_contents( $fname );     if ($recovered) {       // no longer needed:       unlink( $fname );       $recoveredNode = unserialize( $recovered );       // restore the key values I need to proceed with this node:       $node->stage = $recoveredNode->stage;       $node->rnid  = $recoveredNode->rnid;       $node->iris  = $recoveredNode->iris;       cex_front_update( $node );     }     else {       _dbgReport( '********* failed to read "'.$fname.'"' );     }   } }   I'll be pairing the logic down to only store the key fields I need, but this works! Sure beats upgrading my server at 3x the expense. Anyone else doing something like this?


Why 0.33... is the only expression of 1/3?

I am an undergraduate math student who loves mathematics very much, and I am confused by a math problem.  Given $1/3$, we know that $0.33...$ (there are infinite $3$s) is the decimal expression. But how can we prove that it is the only decimal expression of $1/3$?  Sorry for my mistakes for my wrong math typing and not good English. Thank you very much for your answers!


The  (click on your number of helpful flags in your profile) is cool, however some posts have a gray background, some don't. What does it mean?  example:


Keyboard shortcut to minimize a window on Ubuntu 18.10

How can I minimize a single window in Ubuntu?  I have looked in the keyboard shortcuts and there is a maximize windows but there isn't a minimize windows.


Stack Overflow technology and Q&A engine

I just love the technology and design underlying Stack Overflow. They way questions are written, answered, evaluated, the way users get reputation and privileges, how tags are created in a  way, etc.   I wonder if Stack Exchange has made part of this technology available to webmasters who would like to add a similar Question & Answer (Q&A) engine to their sites. I have seen that Stack Exchange has an , but as far as I know it is just for querying the websites and databases owned by the Stack Exchange team.  Does anybody know if Stack Exchange has released its Q&A engine, or if there is any similar technology available for free?


Showing that $\lim\limits_{n\to\infty}x_n$ exists, where $x_{n} = \sqrt{1 + \sqrt{2 + \sqrt{3 + ...+\sqrt{n}}}}$

Let $x_{n} = \sqrt{1 + \sqrt{2 + \sqrt{3 + ...+\sqrt{n}}}}$  a) Show that $x_{n} < x_{n+1}$  b) Show that  $x_{n+1}^{2} \leq 1+ \sqrt{2} x_{n}$  Hint : Square $x_{n+1}$ and factor a 2 out of the square root  c) Hence Show that  $x_{n}$ is bounded above by 2. Deduce that $\lim\limits_{n\to \infty} x_{n}$ exists.  Any help? I don't know where to start.


How to correctly enable Desktop Cube in Unity 3D?

I have read several questions regarding how to fix an already enabled desktop cube or the problems it had in 11.04. But in 11.10, how can I correctly enable desktop cube in Unity 3D?


American traveling to Switzerland 5 days before work visa is valid

I have a work visa (PhD program in Switzerland) starting from December 20 2015-March 19 2015. It is my understanding that during this time, I must obtain my residence permit which allows me to remain/leave/return to Switzerland after my visa expires. I would very much like to purchase a flight on December 15th, 5 days before my visa is valid. As an American, I can travel to Switzerland as a tourist for 3 months without a visa. Would it be acceptable to go there on the 15th as a "tourist" for 5 days until my visa is valid WITHOUT A RETURN FLIGHT? The Swiss Consulate of SF informed me that this should be acceptable, but they cannot guarantee this.


Increment Page Order As Pages Are Created

In the Admin Panel, is there a way to hook into the page creation and increment Page Order number of each page or to be equal to the number of pages. Right now the default is 0 and when I make a new page i would much rather have it at the bottom of my list than the top.


How to synchronise the acceleration, velocity and position of the monsters on the server with the players?

I'm building an MMO using Node.js, and there are monsters roaming around. I can make them move around on the server using vector variables acceleration, velocity and position.  acceleration = steeringForce / mass;  velocity += acceleration * dTime;  position += velocity * dTime;  Right now I just send the positions over, and tell the players these are the "target positions" of the monsters, and let the monsters move towards the target positions on the client with a speed dependant on the distance of the target position. It works but looks rather strange.  How do I synchronise these properly with the players without looking funny to them, taking into account the server lag?  The problem is that I don't know how to make use of the correct acceleration/velocity values here; right now they just move directly in a straight line to the target position instead of accelerating/braking there properly. How can I implement such behaviour?


Cannot chown, chmod on mounted ntfs partition

I need to mount a ntfs partition and be able to use it with unix file system permissions. The problem is that, when I mount the partition using the following fstab entry, I cannot run chown and chmod successfully. It executes without error, but the file access rights are not changed.  PARTUUID=c3e3b171-d451-44e6-9f17-ffbe9e220dc7   /mnt/mounted_drive  ntfs-3g  defaults,umask=0022,uid=1000,gid=1000,errors=remount-ro,permissions 0 2   When I mount the partition without setting umask, uid, and gid I can use previously mentioned commands successfully.  PARTUUID=c3e3b171-d451-44e6-9f17-ffbe9e220dc7   /mnt/mounted_drive  ntfs-3g  defaults,errors=remount-ro,permissions 0 2   What shall I do to mount the partition properly?


Can I look at the upgrade log after a distribution upgrade?

I've upgraded to Ubuntu 12.04 and did it . I didn't look at the "packages to remove" section before clicking next - I've done Ubuntu upgrades many times and assumed it was just the normal set of obsolete library packages etc. But I do tend to watch the terminal text go by and see what it's doing, and I saw it removing a number of packages I wanted. I guess these are packages that aren't on the CD that can't co-exist with the new Ubuntu.  Anyway, I want to find which packages have been removed. So does the update log get saved somewhere?  Then I can start doing some grepping on it and then reinstall the packages I did want.


Installing Ubuntu in Boot Mode UEFI and secure boot on.Any Problem?

I am using Windows 8.1 with UEFI Boot Mode and secure boot is on. I read somewhere that you should turn off secure boot to install Ubuntu properly. I had installed Ubuntu on my different laptop and it is working fine with Windows 10 along with Ubuntu on UEFI boot and secure boot OFF.Now i want to install Ubuntu on my laptop with windows 8.1 previously installed.So,the question is that,is there any problem to install Ubuntu on it with secure boot ON,or i have to change secure boot to OFF?


how to drop a column if exists in mysql?

ALTER TABLE user DROP COLUMN registered_date   We can drop a column using the above command. But how can i drop it only if the  column registered_date exist?


$\int^\infty_0 \frac{dx}{x^n + 1}$, n odd

Well, I saw this integral :  $$\int^\infty_0 \frac{dx}{x^n + 1}$$  on some questions (like this one :  )  But it has always been for $n$ even. Is there something wrong with $n$ odd ? Is not, how do you compute this ? by the same argument ?  thank you and sorry if this is easy. I can't figure out how to do it since it's neither odd nor even.


Force ssh to not print "Remote host identification has changed" warning

Is there a way to avoid ssh printing warning messages like this?   @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@   Although the remote host identity has changed but I know it is fine and  just want to get rid of this warning.


How can I do ping in pure python library?

Is there any library can do "ping" in pure python library and return like True or False. Currently I am using subprocess  for that


I'm an occasional biker. I bought a mountain bike (nothing fancy) with the idea that I might use it off-road or on mountain trails (of which there are many here in Calgary). However, since I've bought it I've done nothing but bike in the city on streets and paved bike trails.  Is there anything worth doing to my bike to convert it to something more suited to urban biking? In particular, the tires have me wondering; they have large rubber off-roading lugs that surely aren't doing me any favors on pavement. I'm not looking to spend a tons of money on a retrofit, but will do so if its worthwhile.


I would like to ask why in this  at 2:30 time mark a girl says "If this were full, that would have been really badass". Instead of "If this had been full, that would have been really badass" (everything in the past) or "If this had been full, that would be really badass" (condition in past result in present)?  From what she said it sounds to me like she says that the cup should be full now (present) and that it "would have been badass" in the past which doesn't make sense to me. I would be fine with either both parts of the sentence in past or condition in past and the result in present but I'm confused with the wording which was used. That's at least how I was taught it.  Thank you.  EDIT: To make sure it's understood what puzzles me:  Sentence: If this were full, that would have been really badass.  Means to me: But it is not currently full and that is why it wasn't badass before.  (this is what it means according to any grammar book, website I went through since ages ago, for  but googling gives tons of other cases). But if that mug was full right know then it couldn't had been spilled before because if it had been spilled (before) then right after the mug could never be full (logic).


Why isn't an injection defined with an iff?

Suppose that $f:X \rightarrow Y$ is a function.  Then an injection can be defined as:  $$\forall x_1,x_2 \in X, f(x_1) = f(x_2) \Rightarrow x_1=x_2$$  Why isn't it defined instead as follows?  $$\forall x_1,x_2 \in X, f(x_1) = f(x_2) \Leftrightarrow x_1=x_2$$  I think the above statement also captures the situation described by the definition of an injection in words, which is:     If no element of $Y$ is assigned to more than one elementof $X$, i.e. the function takes a different value for each point of the domain.   I can see that the definition is missing the phrase "if and only if". So is that the only reason we don't write "$\Leftrightarrow$"?


What would a map of the world look like if lat/longs were treated as projected coordinates?

I'm not quite sure if I'm phrasing this right. It's just occurred to me that lat/longs are two dimensional coordinates like any other projected coordinate system, so it's presumably possible to create a two dimensional map based on these unprojected coordinates.   It would obviously be centred on the point (0,0) (off the west coast of Africa, on the equator), and the 180 meridian would be exactly on the left and right borders.  Is there a name for this kind of "non-projection"? Presumably there are images of it, but I'm just not sure what to look for.


What does $\rightarrow$ mean in $p \rightarrow q$

I was looking at an exercise where it asked the following:  $$\begin{array}{ccc} p&q&p\rightarrow q \\ T&T&T \\ &\ldots \end{array}$$  So, for the third column, I just put $T$ which was correct but I didn't understand what $\rightarrow$ meant. I have seen $\implies$ but I haven't the arrow. Are they the same thing?  Thanks a bunch!


What is the benefit of Skulljacking enemies after the first one?

In XCOM 2, the storyline requires the player to      Skulljack an Advent officer. This triggers what is (at that   stage in the game) a difficult fight.   The option remains to do this to other enemies, and indeed there's an achievement for doing it to every type of enemy. What is the benefit of doing this?


Where is the best place to show validation/error messages in a form?   Beside a field? underneath a field? Reserve an area on the top/bottom of the page, and show any error/successful message there?


how to not-delete-a-file with some-command  file.txt

I've done this before, expect to mutate a file in place, something like $ tr '\t' ',' <file.txt >file.txt and well, clearly the > redirection truncates the file before < can read it; How do I mutate a file inplace without truncating/deleting it?


What is the exact purpose of length padding in Merkle–Damgård hash functions?

Is a length padding technique in a hash function used to avoid length extension attacks ?


Beta Command Line Tools offered as update—why?

Today the App Store is offering me the Command Line Tools for Xcode 10.0 beta 1.  I do not recall ever signing up as a beta tester for any Apple software. Why do I get this update and how can I prevent such beta software from being accidentally installed on my system? I have macOS 10.13.5 and Xcode 9.4. I also have MacPorts with clang 6.0 (newer than the one in Xcode, but it shouldn't interfere).  Update 2019-06-04: It is happening again, this time it is offering "Command Line Tools beta 1 for Xcode 11.0". This seems to be a mistake on Apple's part again (see the accepted answer). Update 2020-09-15: Again with "Command Line Tools beta 5 for Xcode 12.0".


This iPhone cannot be used to create another Apple ID

I have been an Android user for the past few years, and recently switched to an iPhone. I was given a used iPhone 6 by someone. But when I try to create an Apple ID, I get an error message stating, This iPhone cannot be used to create an Apple ID and prompts me to the website even after I reset the iPhone completely and removed all the previous accounts and settings.  Why does Apple not allow creating multiple IDs from an iPhone?


How can I cleanly remove Homebrew. I might have a faulty older installation, and I'd like to have a fresh start.


I was checking code and I came across the following snippet:  int check(char *a) {      (void)(a);//What is this line doing??     return 0; }  int main(void)  {      char *p;     p=(char *)malloc(sizeof(char));     check(p);     return 0; }   What is (void)(a); doing?


After a command is entered in a terminal I am then asked for a password but the terminal freezes and won't let me enter the password. How do I fix this.


What is a one-word synonym for "science lover"?

I'm searching for a one-word synonym for "science lover". In my case, I love science and I self study it, but I never got a degree in Physics or Chemistry or any of these related subjects (except computer-science). But I enjoy experimenting stuff and see what's going on.  So, what would be a one-word good alternative for "science lover"?  The best one I found is learner, but that's more general I guess. Scientist is probably too much in my case. I saw sciencophile in another post, but I don't really like it–it sounds too complicated.


Wolfram Alpha says this limit is $e/2$, which I believe plotting the sequence, however I'm struggling to prove this. I've tried to apply l'Hopital or Cesaro-Stolz to no luck. I suspect I need to cleverly manipulate the binomial expansion, but I just make a mess. Thanks.


How long will this appliance run from a battery?

How long can I run a water pump which requires 12V and 50W from a 12V, 40Ah, 400A car battery?  Can you explain how this was calculated?


In C#, why can't a List object be stored in a List variable

It seems that a List object cannot be stored in a List variable in C#, and can't even be explicitly cast that way.  List<string> sl = new List<string>(); List<object> ol; ol = sl;   results in Cannot implicitly convert type System.Collections.Generic.List<string> to System.Collections.Generic.List<object>  And then...  List<string> sl = new List<string>(); List<object> ol; ol = (List<object>)sl;   results in Cannot convert type System.Collections.Generic.List<string> to System.Collections.Generic.List<object>  Of course, you can do it by pulling everything out of the string list and putting it back in one at a time, but it is a rather convoluted solution.


differentiation using formal definition i.e. $(x+h)$

Using first principles, differentiate $$f(x)=(x)^{\frac{3}{4}} $$  So$$\lim_{h\to 0}\frac{f(x+h) -f(x)}{h} = \lim_{h\to 0}\frac{(x+h)^{\frac{3}{4}} -(x)^{\frac{3}{4}}}{h} $$  I cant seem to solve this question. I'm supposed to get the   output $\frac{3}{4}x^{-\frac{1}{4}} $


The microphone is not recognized (Kubuntu)

So I installed Kubuntu today (mic worked on Windows). The speakers work fine, but the mic doesn't and I think it is not even recognized.   Clearly Kubuntu doesn't recognize the mic. And since Windows did recognize it, I doubt the cause is mechanical. What should I try to solve the issue? EDIT: I tried taking the speaker cable out and in and I got a signal while doing this, but I didnt get a signal while putting the microphone in the microphone input, but I get it if I put it in the speaker input. EDIT2: Curiously, the microphone works if only the microphone is plugged in but not the speakers??? EDIT3:If I plug the microphone first, the microphone works and the speakers don't. Anyone has any idea?


I have stored image to inputstream from html,so i want to store the inputstream to folder in my drive

Part filePart = request.getPart("barcodePhtotoVen");  inputStream = filePart.getInputStream();   How to write this using outputstream to folder/file in my computer drive?


How to trigger a second drop-down list when selecting a coded value in ArcGIS?

I am making a drop down list inside an attribute table of car makes, but want to have a list of models from the respective maker populate when I select a make.  Example: I select Ford in my CAR_MAKE field My CAR_MODEL field would populate with models that Ford makes.


How can I type ASCII characters like Alt + numpad in Windows?

On Windows, the key combination Alt + 2+ 5+ 5 creates a blank space. How can I achieve this on Ubuntu?


how to delete all data from SQLite table in android java

I want to delete all data from SQLite table when I click the button then It create pdf file and then delete the data from the table I have created pdf file but not able to delete to the complete record it show error //Dbhandler code   public void deleteAll() {     SQLiteDatabase db = this.getWritableDatabase();     db.execSQL("delete from "+ TABLE_Users);     db.close(); } //main activity code   document.close();  if (myPath.exists())     myPath.delete();  openPdf(path); // here I want to call the delete all user  dbHandler.deleteAll();          logs  2021-04-08 08:22:00.213 13776-13803/com.j.usamaelectronics E/EGL_adreno:   CreateContext rcMajorVersion:3, minorVersion:0  2021-04-08 08:22:00.288 13776-13803/com.j.usamaelectronics E/EGL_adreno: tid   13803: eglSurfaceAttrib(1582): error 0x3009 (EGL_BAD_MATCH)    2021-04-08 08:22:09.227 13776-13803/com.j.usamaelectronics E/EGL_adreno:    tid 13803: eglSurfaceAttrib(1582): error 0x3009 (EGL_BAD_MATCH)   2021-04-08 08:45:31.035 13776-13776/com.j.usamaelectronics    E/AndroidRuntime: FATAL EXCEPTION: main  Process: com.j.usamaelectronics, PID: 13776  java.lang.NullPointerException: Attempt to invoke virtual method 'void   com.j.usamaelectronics.DbHandler.deleteAll()' on a null object reference at com.j.usamaelectronics.ShowallsaleitemActivity.createPdf(ShowallsaleitemActivity.java:197) at com.j.usamaelectronics.ShowallsaleitemActivity.takeScreenShot(ShowallsaleitemActivity.java:163) at com.j.usamaelectronics.ShowallsaleitemActivity.access$000(ShowallsaleitemActivity.java:46) at com.j.usamaelectronics.ShowallsaleitemActivity$1.onClick(ShowallsaleitemActivity.java:107) at android.view.View.performClick(View.java:5637)


I have problems proving this equality: $$1+\frac{n}{1!}+\frac{n*(n-1)}{2!}+\frac{n*(n-1)*(n-2)}{3!}+...+\frac{n*(n-1)...3*2}{(n-1)!}+\frac{n!}{n!}=2^n$$  Tried various options in inductive step of separating each addends that didn't help much.  EDIT: Any other way of solving this other then using Newton's binomial theorem ? I'm looking for a basic induction.


Addiction and addictive traits seem common amongst animals.  A  shows it's been studied in everything from humans to worms.  My personal favorite of these is:    Is there/was there something adaptive about addictive behaviour? Alternatively, how it is that addictive behaviour survived/persists if it is not adaptive?


For example, if I wrap my content with
 tags (for no reason, just for arguments sake), would that cause a difference to search engines? Does thinner markup improve SEO?

Text text text text text...

    versus

Text text text text text...

    versus
Text text text text text...
         From an SEO standpoint, are these all equal or not?


Finding the maximum likelihood estimator (Theoretical statistics)

Let $X_1, X_2, ..X_n$ represent a random sample from this pdf:  $$f(x|\theta)= \frac{3x^2}{\theta^3}, 0\leq x\leq \theta$$ (with 0 elsewhere)  Could someone explain how I would find the maximum likelihood estimator (MLE) of this pdf? I know I have to get the likelihood function L, then the log likelihood function, then differentiate, but I am getting lost in the calculations. Thanks!


How to assign a variable outside php function

I would like to be able to assign the name of a variable outside the function so that the function can assign the chosen variable. It does not seem to work. Anyone have any ideas?  Below is my attempt, however the $admin variable is empty after running the function.  function assign_check($variable, $check) {     if (empty($_POST[$check])) {         $variable = "no";        } else {         $variable = $_POST[$check];     }        }  assign_check('$admin', 'admin');   My question is not about the use of global variables.


I try to type a command, to get Pinta (because GIMP isn't here for some odd reason)      (Command is sudo add-apt-repository ppa:pinta-maintainers/pinta-stable/ubuntu),    and it says      asbell is not in the sudoers file.  This incident will be reported.    Any idea how to fix this?


Possessive of a word that is already possessive

If the cricket ground Lord's is a possessive, what if you want to describe something belonging to Lord's? Would you say:     I was very impressed by Lord's's customer services.   It doesn't look right, so what is the correct way of writing it?


Find a sub-ring of M(2, $\mathbb{Q}$) which is isomorphic to $\mathbb{Q}$

I believe that for a subring to be isomorphic it needs to be a ring homomorphism but i'm not sure how to go about finding isomorphic rings, I'm not looking for a straight up answer I'm trying to understand how to go about the question.


PGFPlots - Legend box aligning with axis

I am trying to increase the size of the legend such that it exactly fits to size of the plot. But even after having a look at the PGF manual I could not figure out how I can realise my plan. Afterwards I want to equally distribute the legend entries within the box.  UPDATE  The actual solution was:  \def\WIDTH{7cm} \def\INNERSEP{3pt}  \begin{axis}[     xmin=1, xmax=10, xtick={1,...,10}, xmajorgrids=true, xlabel={Cores},     ymin=0, ymax=100, ymajorgrids=true, ylabel={MFLUPS/s},     scale only axis,  % <==== !!!!!!!     extra description/.code={         \node[         draw,         text depth=0pt,         at={(current bounding box.north-|current axis.north)},         anchor=south,         text width=\WIDTH-2*\INNERSEP,         inner sep=\INNERSEP,         outer sep=0pt,         ] {     \hbox to \linewidth{%         \hfill \ref{A} A \hfill \ref{B_B} B \hfill         }%     }; }, ]        \documentclass{standalone}  \usepackage{tikz}  \usepackage{pgfplots} \pgfplotsset{compat = newest}  \begin{document} \pgfplotsset{width=7cm} \begin{tikzpicture}  \begin{axis}[     xmin=1, xmax=10, xtick={1,...,10}, xmajorgrids=true, xlabel={Cores},     ymin=0, ymax=100, ymajorgrids=true, ylabel={MFLUPS/s},     legend style={         at={(current bounding box.north-|current axis.north)},         anchor=south,         legend columns=-1,         outer sep=0     }] \addplot [mark=square*, mark options={solid}, thick] table { 1   10 2   20 3   30 4   40 5   50 6   65 7   70 8   80 9   90 10  95 }; \addlegendentry{Graph A} \addplot [mark=*, mark options={solid}, thick] table { 1   10 2   20 3   25 4   40 5   25 6   65 7   70 8   25 9   90 10  95 }; \addlegendentry{Graph B} \end{axis} \end{tikzpicture} \end{document}


Binomial coefficients identity: $\sum i \binom{n-i}{k-1}=\binom{n+1}{k+1}$

I am trying to prove  $ \sum_{i=1}^{n-k+1} i \binom{n-i}{k-1}=\binom{n+1}{k+1} $  Whichever numbers for $k,n$ I try, the terms equal, but when I try to use induction by n, I fail to prove the induction step:  Assume the equation holds for $n$. Now by Pascal's recursion formula,  $ \binom{n+2}{k+1}=\binom{n+1}{k+1} + \binom{n+1}{k}\\   =\sum_{i=1}^{n-k+1} i \binom{n-i}{k-1}+\binom{n+1}{k}, $  by induction assumption. In order to complete the proof, I would need to show  $ (n-k+2) \binom{n-(n-k+2)}{k-1} = \binom{n+1}{k} $  but the left-hand side is zero. What am I doing wrong?  EDIT:  There were links to similar questions when my question was marked as duplicate. However, these links are now gone, so I add them here as they were useful to me:    -- hint to Vandermont's identity  -- basically the same question, but two days earlier.   (I did search, but did not found these.)


Consistent font-size across browsers (web development)

When creating web pages how do we achieve a consistent font size across browsers. I have used something like "font-size: 11pt; font-family: Helvetica,'Lucida Grande'" in my CSS, but the text looks different in Firefox, IE, Google Chrome and Safari (and this is not even on different platforms). Basically on the same machine, that is running Windows Vista, I get a different look and feel under different browsers.  How can this be fixed so that the size of text appears same on all the different browsers.


Determining if there can be smooth closed geodesic given its curvature

In my class on differential geometry I have been given the following question on which I am stuck:  Let S be a regular orientable surface in $ R^3 $ with Gaussian curvature $K$ (not necessarily constant) and we are to check if there can be a smooth closed geodesic on S in the following case: $ K>0 $ $ K=0 $ $ K<0 $ and we are to give an example when it is possible that the closed geodesic bounds a simply connected region  I know for starters about the first one with positive curvature I may take the sphere and a great circle which is a geodesic and obviously bounds a simply connected subset of the sphere. But with the zero and negative curvatures I have no idea how to tell if a closed geodesic exists I think the Gauss Bonnet theorem has something to do with this but I cannot really proceed from there and I am posting here in the hope of getting help ******* Progress: I can work out what happens with Gauss Bonnet if I have the constraint that the geodesic bounds a simply connected region as this is simple but the fact of the matter is where I am stuck is the general existence or non existence if no constraint is given on the region bounded


My aunt handed me might and magic 6 and I installed the game with the disks and she told me u could open it with steam but she couldn't remember how. How do i open it with steam? Is it even possible?


Is there a way to unit test if a function correctly executes stats and logs in Go?

I'm trying to write a unit test for a function that checks a URL string input and increments some stats using a third party package depending on what that URL string is. Since this function only increments stats and returns, how can this be unit tested?  Right now, I just have a test that basically makes sure the function returns and doesn't segfault. The function returns increments different stats and returns no matter what, so my test will pass for all string inputs.   func handleStats(url string) {     if url == "" {         stats.Increment(metricForEmptyStringURL)         return     }     stats.Increment(metricForNonEmptyURL)     if strings.Contains(url, "${") {         stats.Increment(metricCorrectlyEncodedURL)     } }   This is what I currently have (which is not useful since it'll always pass):  func Test_handleStats(t *testing.T) {     tests := []struct {         name string         url  string     }{         {name: "Blank", url: ""},         {name: "No encoding", url: "http://testurl.com/"},         {name: "With encoding", url: "http://testurl.com/${ENCODING}"},     }     for _, tt := range tests {         t.Run(tt.name, func(t *testing.T) {             handleStats(tt.url)         })     } }   What is the best way to test something like this?


Do you take falling damage after a high jump of over 10 feet?

I have a multiclass Monk / Druid (2 levels of monk).  He cast jump on himself, wild shaped into a brown bear, activated step of the wind, then took a high jump with a height of 42':  High Jump When you make a high jump, you leap into the air a number of feet equal to 3 + your Strength modifier  Strength mod is +4 from the brown bear, so 7 × 3 (jump spell) × 2 (step of the wind) = 42. Our group got into an argument over whether he would take 4d6 falling damage after his high jump, and the PHB doesn't seem to answer this.


ConTeXt: Is there a way to show the \part heading?

I’m new to ConTeXt, and noticed that \part{Some title} (and neither \start part[title={Some title}]…\stoppart) will produce and output (besides an empty page with footer and header). Nevertheless, other settings as \setuphead[part][footer=empty] will have an effect on that page, but I can’t get to display the number nor the title of the \part.  I remember had read in some introductory doc (not sure which one) that this was because the \part command required mostly a special (visual) setup from the editor, but don’t know how this can be achieved (and said doc didn’t go into that). Does anybody know how?


I want an example of a sequence that satisfies $\mid x(n) - x(n-1)\mid \to 0$ but not Cauchy ? I tried to find such sequence  $x(n)=1/2,1/3,1/2,1/3,1/4,1/2,1/3,1/4,1/5,,,,$ it's not Cauchy since it is not converges (has infinitely limit points) and the difference between any successive terms goes to zero .. I asked my doctor but he said the difference is constant (not zero)since the sub-sequences here are constants  So can any one gives me a hint for this problem :)? thanks in advance ^^


Generating unique ID for instances using Guid in C#

I have a question concerning the Guid as a method to generate IDs. I need to be able to generate a new unique ID for each instance of a given class (I expect there to be a couple of hundreds of instances). I am including my code below:  class Program {     static void Main(string[] args)     {         Instance instance1 = new Instance();         Console.WriteLine(instance1.ID);         Instance instance2 = new Instance();         Console.WriteLine(instance2.ID);         Console.ReadKey();     } } public static class GenerateID {     public static string NewID()     {         Guid guid = Guid.NewGuid();         string id = guid.ToString();         return id;     } } public class Instance {     public string ID = GenerateID.NewID(); }   From what I can see, this method works, and two unique IDs are generated each time when I run the code, but I am not able to test this extensively, since I read that Guid is able to generate like a badgilion of IDs.  Would the way I implemented the above ensure that the ID's are unique each time? Or is there any chance of a collision? If so, what would be a better way to go about assigning unique IDs to instances?  EDIT: Alright, so I learned from ppl's answers that Guid is not inherently 100% unique (thanks, I'll make sure to read up on that), but my question is whether the method I used to get the ID may heighten the chance that the same two IDs will be generated? Or is this a good way to go about obtaining unique IDs?


Let $f$ be a $C^2$ function on $[0,1]$ such that $f(0)=f(1)=f'(0)=0,f'(1)=1.$ Prove that $$\int_0^1[f''(x)]^2dx\ge4.$$ Find all $f$ for equality to occur.


I would like to use Flash Player to show web contents but since today (12 Jan 2021) Adobe is blocking it. Is there a way to use it? I've tried Firefox, Chrome, Safari and Brave browsers.


I (think I) know how to pluralize an indirect quote, e.g.,     Their survey answers were limited to yeses and nos.   But how do I pluralize a direct quote ending in a punctuation mark? Am I even allowed to retain the punctuation mark for emphasis?  In other words, would the correct form(s) be:        There was no shortage of "How do you do?"s and "Let's do lunch!"es at the networking event.   There was no shortage of "How do you do"s and "Let's do lunch"es at the networking event.   There was no shortage of how-do-you-dos and let's-do-lunches at the networking event.   [something else altogether]      Does the number of correct forms change when I elect to italicize quotes, rather than demarcate them with quotation marks?  A/N: I was trying to keep my example short, but I do realize that "how-do-you-do" is already an . Hyphenation seems unwieldy, however, if the quote were longer.


My dad has a PS3, he has not played any games on it with the actual controllers.   When the controller is connected to the usb charger it works perfectly, but when I unplug the remote from the sub which is still in the PS3 the controller's red lights blink then turn off.   I have charged it for 2 almost 3 hours it should work. Why doesn't it?


I have a C++ project divided into multiple library targets and one executable target.  I've been dynamically linking those libraries and am trying to switch to static linking but running into "undefined reference" errors.  One of those errors involved a class named Effect, which is in a library named shading.  The library typography has a class named Type_Effect, which is derived from Effect.  When processing typography the linker cannot find any symbols for the Effect class.  I verified that the libraries are being included like so:  .../shading/libshading.a .../typography/libtypography.a ...   I ran the linker with the -verbose command and part of the output for shading was:  attempt to open .../shading/libshading.a succeeded (.../shading/libshading.a)Shader_Manager.cpp.obj (.../shading/libshading.a)Shader.cpp.obj (.../shading/libshading.a)Program.cpp.obj   Effect.cpp.obj was missing.  I checked the shading.a file and it did include Effect.cpp and all of the related Effect symbols.  Next, I added dummy code for creating an Effect object into my main executable cpp file, and sure enough the linker output now included:  ([...]/shading/libshading.a)Effect.cpp.obj   Alternatively, preceeding linklibs.rsp with --whole-archive forced the linker to load Effect.cpp.obj, but loading everything introduces other problems beyond the scope of this question.  The evidence points to some breakdown in the linker determining which object files to include.  The shading library is not directly used in my main executable target, so the presence of some shader objects being loaded indicates that at least some of the dependency tracing is working.  In the ld flag documentation for --whole-archive, it mentions how that flag     include[s] every object file in the archive in the link, rather than   searching the archive for the required object files.   What is some of the logic behind that searching?  What factors could make or break it?


In Game of Thrones, Daenerys has managed to survive fire or extreme heat in several instances:   When Daenerys' dragons were born in the season 1 finale, "Fire and Blood" (Game of Thrones, S01E10) Killing the khals by locking them inside the temple of Vaes Dothrak and lighting the place on fire in "Book of the Stranger" (Game of Thrones, S06E04) - while all the men burned alive, Daenerys emerged from the hut unscratched. The steaming hot bath in "Winter is Coming" (Game of Thrones, S01E01) - Daenerys is warned by a servant that "it's too hot, my lady", but she steps in without flinching Daenerys casually picks up the dragon eggs that were roasting on hot coals, in "A Golden Crown" (Game of Thrones, S01E06) - when the Dothraki handmaiden, Irri, rushes in and knocks them off her hands, Daenery's hands are unscathed, while Irri's now have burn marks   Here she didn't show immunity to heat, but made a relevant remark:    Her comment, "He was no dragon. Fire cannot kill a dragon", at the time of Viserys' death in "A Golden Crown" (Game of Thrones, S01E06)   George R. R. Martin, author of the novel series that the show is adapting, has stated that the Targaryens are not immune to fire (at least in the books).  Were the above instances in which she is shown to be immune to fire (in the show) unique, or has she had this ability her whole life? If so, when and how did Daenerys acquire this ability?


Show that $X $ is a infinite set ,it is connected in the finite complement topology?

what i had done :let X be a infinite set and there be open sets $A,B$ on it. such that $A\cap B =\varnothing$ or $A\cap B\ne\varnothing$then  $X-A\cap X-B \ne  \varnothing $ .which means there doesn't exist   $X-A\cap X-B = \varnothing $ ,which implies that there is no separation of X in finite complement topology. is this proof correct.


How to detect backdoor origin - ssh brute forced

I've set up a little ARM server, running the latest version of armbian with kernel 4.11.6  I have Apache2:  Server version: Apache/2.4.10 (Debian) Server built:   Jul 18 2017 19:31:53   At home i'm using a cheap router Hawei HG8247H , with port forwarding active for port 80 and port 22 directing the incoming connections to the public IP, straight to the server inside the private network 192.168.1.114  At first i've set up the root user with an too easy of a password that i suspect, was cracked by brute forcing ssh login...  After some thought over the subject i altered the password, switching to a stronger one. My doubt is, was the system compromised to the point where a mere password change of root isn't enough anymore?  I ran the netstat -pan:    There's an abusive IP operating on my machine: 123.183.209.140; Probably serving as a spam zombie while i write this.  Also, ran nmap searching for vulnerabilities, yielding NOT VULNERABLE at least for the ones listed at the vulscan database to this day.   These high ports also seem suspicious. I feel uncanny with all the eerie movements on the server and the idea of a member of the internal network being compromised is scary as it is a trusted node of the internal network. Should somehow try to isolate the server in another separate network.  My doubt is, what is the next step to take from hereafter ?  Thank you for any advises.


Based on the record X1 ,…, Xn what is the unbiased estimation of 1/p

If we investigate $n$ patients for SARS. The indicator of sequence of the trails is $X_i$ ($X_i=1$ is for success and $0$ is not success). And the sequence indicator is available for all n independent SARS patients . Reciprocal probability is $R=1/p$. Reciprocal probability stands for number of trails needed to obtain an expected of a first success. I was wondering that based on the record $X_1 ,…, X_n$ what is the unbiased estimation of $R$?


First of all, I think this is not a variable address copying issue. I have this code : x = [1, 1, 0, 0] b_u = [[0.2 for _ in range(3)]] * 4 for i in range(4):     # The problem is on line below. This line copying new value to the whole column.     b_u[i][0] = (2 * x[i]) / (1 + sum(x)) print(b_u)  And you can see whats happening in lines below : # b_u : # Before loop : [[0.2, 0.2, 0.2], [0.2, 0.2, 0.2], [0.2, 0.2, 0.2], [0.2, 0.2, 0.2]] # Expected : [[0.67, 0.2, 0.2], [0.67, 0.2, 0.2], [0, 0.2, 0.2], [0, 0.2, 0.2]] # After loop : [[0.0, 0.2, 0.2], [0.0, 0.2, 0.2], [0.0, 0.2, 0.2], [0.0, 0.2, 0.2]]  Where am I mistaken? Is it a typo?


Show a given analytic function is constant

Suppose that $f$ is analytic on some region $R\in\mathbb{C}$. If Im$(f)$ = $k\cdot$Re$(f)$ for some nonzero constant $k\in\mathbb{C}$, then show that $f$ is constant on $R$.  I know that if $f'(z)=0$ for all $z$ in some region $R$, then $f(z)$ is constant. However, I'm not sure how to apply this to the question at hand. I also think the Cauchy-Riemann equations could be helpful, but again, I'm not sure how to apply them to the question.  Any guidance would be greatly appreciated. Thank you!


A "swash" font feature differs between XeLaTeX and LuaLeTeX

Compiling this example that uses  font  \documentclass{article} \RequirePackage{fontspec} \setmainfont[Ligatures=TeX]{TeX Gyre Pagella}  \begin{document} \fontspec{EB Garamond}[Ligatures=Historic,Scale=2] Questo altere uniffatto fiato. \end{document}   with XeLaTeX and LuaLaTeX gives two different results: the Q is shown with a long "swash" only in the PDF produced by XeLaTeX. Why?


Is including the loop necessary for page.php?

QUESTION: Is it necessary to include the wordpress loop in page.php? If it is not necessary, why do many themes (including the wordpress 2013 default theme) include it? I noticed  discussion on the wordpress forums, but I didn't understand the final answer. furthermore it is stated,  You use The Loop in your template files to show posts to visitors. (Source:)  BACKGROUND: I am attempting to develop special page templates, and I realized that I don't quite understand what the benefit is of including the loop for pages.php, because after all, pages don't care about posts, that is something that concerns index.php.


I heard phrases like "place nice" and "place safe" several times during watching series and movies and each time I was wondering why an adjective stands after a noun while they teach that adjectives go strictly before nouns. Unfortunately, all what I gained with simple googling is that it could be a set phrase like "Princess royal". And I already checked a  which doesn't answer my question because in this case I see no difference between "a place safe" and "a safe place". Examples:   We always have to go to, you know, someplace nice.     Is there any place safe for her?


Why do files become 'invisible' when execution permissions are revoked?

This is somewhat related to my, now resolved, question here . When I ran chmod 666 on group of files they stopped showing up in the GUI (thunar) but I could see them when I ran ls. When I found out that this was because of execution privileges I ran chmod 775 instead and now I can see them again. I could only see the top level directories and files and the files were 0 bytes in size. Why did this happen?


What is the benefit of Krivine's notation?

I saw some people uses Krivine's notation for function application when presenting the syntax for the $\lambda$-calculus.  For example, the $\lambda$-term $\lambda f . \lambda x . \lambda y . f\ x\ y$ (with the normal convention that function application associates to the left, so it actually means $\lambda f . \lambda x . \lambda y . ((f\ x)\ y)$) is written $\lambda f . \lambda x . \lambda y . (f)\ x\ y$ (with a similar convention that it actually means $\lambda f . \lambda x . \lambda y . ((f)\ x)\ y$).  I do not see the point of having another pair of parentheses around the innermost $f$.  Why do people use Krivine's notation instead of the usual one?


Does diffraction happen from small slit width than its wavelength?

I always learnt in school that diffraction and interference happens if the slit width is of the order of wavelength. But what if the slit width is less than that of wavelength. Does diffraction happens in such conditions? If so then is there a mathematical representation for that?


I'm using Features to create a feature called foo which tracks content types and views so they can be described in code, committed to my repository and eventually pushed into the staging and production servers.  Some modules (e.g , , ) create some views as part of their functionality. The problem is that I can't include those views into my foo feature. So for those specific views I have to repeat (by hand) any customization I did locally to the staging and production servers.  Any ideas?  What I've tried:  1) I tried manually adding the view name in the foo_features.info file:  features[views_view][] = admin_content_node   but when I do drush fu foo_features -y that line is removed and the .info file and the view definition is not being included in the foo_features.views_default.inc file.  2) I had a look into the database:  mysql> select vid, id, display_title, display_plugin, position from views_display; +-----+----------+---------------+----------------+----------+ | vid | id       | display_title | display_plugin | position | +-----+----------+---------------+----------------+----------+ |   3 | default  | Master        | default        |        1 | |   3 | page     | Page          | page           |        2 | |  30 | block    | Block         | block          |        2 | ... |  46 | default  | Defaults      | default        |        1 | |  46 | system_1 | System        | system         |        2 | +-----+----------+---------------+----------------+----------+   That last row (vid: 46, display_plugin: system) seemed suspicious so I've changed (directly via SQL) system to page. I then did drush cc all and retried the process at [1] for including the view into the feature but without luck. I tried this because I thought that "system view displays" (whatever that means) cannot be included in features.


Have there been any recent attempts to falsify the  hypothesis alternative to the Doppler shift explanation for the red shift, or is it simply ignored like the pilot wave quantum mechanical hypothesis alternative to the Copenhagen hypothesis of quantum mechanics has been? What new evidence would it take to get the tired light hypothesis for the red shift reexamined as the recent fluid dynamics oil drop experiments have done for the pilot wave hypothesis of quantum mechanics?


Apache presents wrong certificate when accessed via load balancer

I've got a server that has two SSL certificates set up, one for internal access where it is accessed along the lines of host.my-local.net and other for external access where it is accessed similar to 185.185.185.185 (this is not the actual IP address, but it is an IP address as there is no host name assigned to it).   When accessed via the external address, the connection is going through a load balancer / firewall which I don't have any access to, all I know is that it translates incoming connections on a specific port into the internal address on the SSL port.  The problem is, when an external connection comes in, I get browser warning that the site is masquerading as host.my-local.net; it is presenting the certificate for host.my-local.net instead of 185.185.185.185.  I have a virtual host set up for both names in my apache2 config file, so I assume that for some reason the server is having trouble distinguishing between an external connection and a LAN connection.  I haven't had this problem with a simple NAT, so I don't know why it would make a difference if the load balancer is making the request look like it's coming from the LAN instead of internally.  I have verified that the browser I am using support SNI (Google Chrome) and Apache 2.4 apparently supports it out of the box without requiring the NameVirtualHost directive.  However, the documentation says:  In 2.3.11 and later, any time an IP address and port combination is used in  multiple virtual hosts, name-based virtual hosting is automatically enabled  for that address.   However, it's not the same IP address used in the two different virtual hosts, one is the internal (LAN) IP address and one is the external (world visible) IP address, so does that apply here?  To clarify my configuration, I have two virtual hosts set up, like so:  <VirtualHost 185.185.185.185:443> # here i specify the certificate for 185.185.185.185, e.g. SSLCertificateFile /etc/ssl/private/185.185.185.185.crt </VirtualHost> <VirtualHost host.my-local.net:443> # here i specify the certificate for host.my-local.net, e.g. SSLCertificateFile /etc/ssl/private/host.my-local.net.crt </VirtualHost>


Java program encountering NullPointerException, what part of this program went wrong?

This is from my data structure class, We were asked to add two numbers represented by linked list. The numbers are backward, which means the least significant digit is at the front of the list. This program runs fine when the sum is less than 10. but when I have something like 9+2, eclipse shows this "Exception in thread "main" java.lang.NullPointerException"     Here is the constructor      DigitNode(int digit, DigitNode next) {             this.digit = digit;             this.next = next;     }  public static BigInteger add(BigInteger first, BigInteger second) {          BigInteger newList = new BigInteger();            DigitNode ptrF = first.front;            DigitNode ptrS = second.front;            DigitNode ptr = newList.front;             if(first.negative == second.negative) {//both positive or negative                   newList.negative = first.negative;                    int sum = 0;                   int carry = 0;                   int Fvalue= 0;                   int Svalue = 0;                    while(ptrF != null ||ptrS != null || carry != 0) {                       sum = 0;                       if (ptrF == null) {                           Fvalue = 0;                       } else {                           Fvalue = ptrF.digit;                       }                        if (ptrS == null) {                           Svalue = 0;                       } else {                           Svalue = ptrS.digit;                       }                          sum = Fvalue + Svalue + carry;                       carry = 0;                        if(sum > 9) {                           sum = sum%10 + carry;                           carry = 1;                       }                       if(newList.numDigits == 0) {newList.front = new DigitNode(sum,newList.front); newList.numDigits++;}                       else {                         ptr.next = new DigitNode(sum, null);                       ptr = ptr.next;                       newList.numDigits++;                    }                              }}             System.out.println("Parsing result:");             System.out.println("Number of Digits: " + newList.numDigits);             for (DigitNode ptrtest = newList.front; ptrtest != null; ptrtest = ptrtest.next) {                 System.out.print(ptrtest.digit + " - > ");             }             System.out.println();            return newList;      }   I'm getting the warning at this line " ptr.next = new DigitNode(sum, null);"


How Do I Reset my Ubuntu Password on a Laptop That Came with Windows 8 Pre-installed?

My laptop came with Windows 8 pre-installed and uses UEFI (the successor to BIOS) by default. It has been working fine for me for a few months. I decided to install Ubuntu with the goal of a conventional dual-boot setup. I disabled Windows 8's Secure Boot and Fast Startup features to avoid any problems these might cause and shrunk my primary partition by 13 GB from within Windows 8 so that there would be some free space in which to install Ubuntu. I downloaded Ubuntu 12.04.3 on a separate Linux machine and used the ISO file to create a bootable USB drive with . Then I booted my Windows 8 laptop from the USB drive, and successfully installed Ubuntu in the previously allocated free space. Then, dumb me, I immediately forgot my new password. When I reboot my machine it always brings me to Ubuntu without any prompts. I tried  to reset my Ubuntu password, but when I try pressing or holding the left Shift key at any point during the boot sequence, the boot sequence simply continues uninterrupted.  The page about recovery mode linked to in the previous sentence says that if I restart (as opposed to power down and power back on), I should meet with a prompt to enter recovery mode, but I don't. Any suggestions that would (a) enable me to boot Windows 8, (b) enable me to recover my password, and/or (c) enable me to re-install Ubuntu completely would be greatly appreciated. I have read that running Boot Repair would enable me to boot Windows 8, but as far as I understand that requires super user privileges (sudo).


the title is inscribed in the spine or the title is inscribed on the spine? What is right and where is the difference? And is it right to say: Words were inscribed on the sign?


How to find out which file or folder is being locked by process in Windows OS?

Once in a while, I run the task manager and see several processes with the same name (e.g. comskip) running at the same time in the background while looping or using most of computation power (because it is dealing with a corrupt file). I know the exact folder from which that process is using files from, but there are just too many files in that folder that It would take me days to go through each file and determine the process that locks them (which I know how to do). My concern: I would like to reverse this way of establishing that relationship. From a known running process in the task manager, I would like to determine the file that that process has locked and not the other way arround.


How long does it take to index the page?

I published my web-app 1 week ago and it took 2 days to be indexed. But I made some changes to the HTML to improve the SEO four days ago and the changes have not yet been indexed even with the number of visits increasing. the changes are already on the site, but not on the search console. Is there any way to speed up the process?


Ubuntu 18.04 LTS - missing suspend option when power button is pressed

After installing Ubuntu 18.04 LTS when I press the power button there is no option for sleep or suspend.  How can I get these options to show up?


Prove $f[X]\backslash f[X']\subset f[X\backslash X']$

edit: $f[X]=\{f(x):x\in X\}$  $f[X]\backslash f[X']\subset f[X\backslash X']$  Simple: Proof by definition. What I would like to provide is a counter-example and intuition to the reverse of this question. Please correct me if I am wrong. If it is correct, I hope this could serve as a reference to the textbook which I can't find its solution in the internet.  $f[X\backslash X']\subsetneq f[X]\backslash F[X']$  Counter-example: constant mapping   $X\cap X'=\emptyset,A=X\cup X',B:\{y\}$ $f:A\rightarrow B\;s.t.f(x)=y\;\forall x\in A$ $f[X\backslash X']=f[X]=\{y\}=f[X']$ $f[X]\backslash f[X']=\{y\}\backslash \{y\}=\emptyset$ $\{y\}\subsetneq\;\emptyset$   Intuition:   $A\subset\emptyset\equiv\;False$ $f[X]=f[X']\rightarrow f[X]\backslash f[X']=\emptyset$ $X\cap X'=\emptyset\rightarrow X\backslash X'=X\;and\;X\neq\emptyset\;and\;X\neq\emptyset$ $f[X]\subsetneq\emptyset$   So it all depends on which is which--either you find constant mapping or manipulation on statement calculus mechanical.


Does $X$ (a random variable) usually refer to the population or the sample?

Like the title says, does $X$ (a random variable) usually refer to the population or the sample?


What are the recommendations of software products for creating automated backups of SQL Server 2008 databases?  The backup should happen without taking the database offline/detatching.


Where/how do I get chrome for ubuntu 16.04

I have looked in the default software installer but it's not there. I saved it to my downloads from the website and go to 'open the folder' but it doesn't work.  It says "the MIME type of this file is 'application/x-debian-package' and can not be installed on this system. Any help?


If f and g are uniformly continuous then fg is uniformly continuous

Given that $f,g:(a,b) \rightarrow \mathbb{R}$ and both uniformly continuous on $(a,b)$ .... Can we say that $fg$ is uniformly continuous? .... If not please provide a counter-example and if true please provide me a hint  Thank you


I am doing work for and OS class and for some reason bcc needs a memcpy even though I haven't called it in the code and its unavailable, so I'm rolling my own, however it keeps segfaulting `  void memcpy( void* destination, void* source, size_t bytes ) {         size_t i = 0;         char* destination__ = ( char* ) destination;         char* source__ = ( char* ) source;         if( !( destination__ == source__ ) )         {                 for( ; i < bytes; ++i )                         destination__[ i ] = source__[ i ];         } }   It seems to segfault and I am not sure why, it does fine when things are malloced but not for something like the following.  `  char* foo = "Hello"; char* bar = "Goodbye"; memcpy( bar, foo, 5 );   I have a feeling this is because foo and bar are likely global data, and it has something to do with that but Im not sure. I wouldent be asking except for the fact that I have found other implementations  are  same/ online  It crashes when compiled with regular ol' gcc which Im using to validate outside the OS Im building that has no diagnostics. Im confused as to why this is happening.


Stuck In login loop after updating my system to Ubuntu 18.04

I updated my system from Ubuntu 16.04 to Ubuntu 18.04 and after updating when I am starting my machine it's asking me for login password and when I am typing the correct password one blank screen appears and it's again asking me for the password and the same thing happening again and again. I saw some answers on the internet for this problem and everyone says to press Ctrl + Alt + F1 on login screen to enter into console and follow some commands as they mentioned but whenever I am pressing Ctrl + Alt + F1 or F2,F3,.....,F9 nothing is happening and I can't see any console and I am still on the login page. Please help me guys to get rid of this problem. I will be very happy if you can help me 🙂


Should we give users a link to their question that has no activity in over a year?

Users occasionally forget about the questions they asked. These are questions that may require editing or review to obtain more acceptable answers. Would it be appropriate to remind OPs with a link to a dead (but not closed) question to encourage them to review or edit it? Perhaps the link could be given in an alert after the question has been dead (and unaccepted) for a year or longer.


Find all strings of length 4 over the alphabet {0, 1, 2} with the property that there are no 10, 21, or 20 substrings.

What is the formula for doing this type of problems?


Proof Verification: Consequence of Bertrand's Posulate and Sums of Primes

I am currently self-studying number theory in high school, and came across this question:     Assuming that for every integer $n>1$, there exists a prime number between $n$ and $2n$, prove that every positive integer can be written as a sum of distinct primes or $1$ more than a sum of distinct primes.   My attempt:    We use induction on $\Bbb N$.  Clearly, $1$ can be written simply as $1$, thus the conjecture is true for $1$. We assume that the conjecture is true for all numbers up to some $k\in \Bbb N$.  Now, we take $k+1$ and find out $\Bigl \lfloor \frac{k+1}{2} \Bigl \rfloor.$ By Bertrand's Postulate, there must exist primes between $\Bigl \lfloor \frac{k+1}{2} \Bigl \rfloor$ and $2\Bigl \lfloor \frac{k+1}{2} \Bigl \rfloor$, where $2\Bigl \lfloor \frac{k+1}{2} \Bigl \rfloor \leq k+1.$ By the well-ordering principle, the set of primes has a least element, say $p$. We find out $(k+1)-p$.  Now by our induction hypothesis, the number $(k+1)-p$ can be written as the sum of distinct primes, none of them $p$ since $p>(k+1)-p$. Let them be $p_1, p_2... p_n$.  Thus we can write   $$k+1=p+p_1+p_2+...+p_n$$  which concludes our proof.    Is the proof correct? Is there a better way to do it? I have a distinct feeling that it is possible to do this through a proof by construction, in which we find the primes through a similar argument.  Edit: My question is not a dupicate because the other question's top answer is not clear enough and only provides a hint. The other answers are not satisfactory.  Further, this is a proof verification question, and my final statement 'can this be proved by a proof by construction' is not addressed in the other question.


Linear independence of duplicate vectors

I have a question about the definition of linear independence. I saw a definition below in my course. Definition A set of vectors $\{v_1, \cdots v_n\}$ is linearly independent if the equation $c_1 v_1 +\cdots c_n v_n = 0$ has only the trivial solution $c_1 = \cdots =c_n =0$. The set is called linearly dependent otherwise. When I saw this, I wondered: what if $v_i$ are all the same? For example, Is $\left\{\begin{pmatrix} 1 \\ 0 \end{pmatrix},\begin{pmatrix} 1 \\ 0 \end{pmatrix}\right\}$ linearly independent? My thought is that, since set with the same element $\{a,a\}$ is equal to $\{a\}$, as we see , so $\left\{\begin{pmatrix} 1 \\ 0 \end{pmatrix},\begin{pmatrix} 1 \\ 0 \end{pmatrix}\right\}=\left\{\begin{pmatrix} 1 \\ 0 \end{pmatrix}\right\}$ must hold, and this set is linearly independent. Is this correct? if not, why? This question arose when we were discussing the statement "$n+1$ vectors in $n$-dimensional vector space are linearly dependent". If my argument is correct, I think this would be false.


Displaying a counter that is computed later

Most probably a trivial question for you: I have a counter \thetotalnoexercices that I compute while compiling my book, but I want to refer to it in the introduction ("This book contains ... exercises"). I should write it to the .aux file but the mechanism seems unclear to me (according to my trials!). Many thanks in advance! Best, O.


Elementary proof of existence of irreducible polynomials of arbitrary degree in $K[X]$ for $K$ a field

I am trying to prove without any galois theory that, for a finite field $K$, there exists irreducible polynomials of arbitrarily large degree. There are answers using Galois theory on MSE, e.g.  My current thought is as follows, although I am uncertain as it seems too simple: Suppose all irreducible polynomials are degree $\leq n$, then as our field is finite, we can enumerate all the irreducible polynomials $P_1, ... P_s$. We then consider $G=\prod_{j=1}^{j=s}P_j +1$. Next, as $K$ is a field, $K[X]$ is a euclidean domain, and hence a PID, and therefore a UFD. In a UFD primes and irreducibles are equivalent. Therefore, if $G$ is not irreducible, we can factor it as a product of powers of $P_1, ..., P_s$. Without loss of generality, suppose $P_1$ divides $G$. Then we can write $G=P_1f$, and $1=P_1(f-\prod_{j=2}^{j=s}P_j)$. However, as $K$ is a field, and therefore also an integral domain, clearly $P_1$ cannot have an inverse as by definition an irreducible element is not a unit. (for context, I came across this question in a past paper for our introductory course on Groups Rings, and Modules. We haven't covered Galois theory*, and normally questions for the irreducibility of polynomials we are expected to use eisenstein's criterion, Gauss' lemma and elementary arguments. *for example, terms like 'splitting field' and 'field extension' are not defined in the course. Also for context: I switched into the second year of a maths degree from economics, and am not particularly confident with abstract algebra compared to areas like real analysis and statistics , so apologies if this is an unintelligent question) Thank you very much for your help :)


Integration over a set defined using inequalities

I was hoping to get some help in understanding the solution provided below. I understand that the integral will evaluate to $\frac{1}{n!}$, however, my uncertainty lies in how the integral is setup. I am not sure how we use $C$ to setup the integrands. Why would it not be $${\int_0^1 \int_0^{x_n} \dotsb \int_0^{x_3} \int_0^{x_2} \int_0^{x_1}} ds_1 ds_2 \dotsc ds_n?$$. Let $C$ be a set in $n$-dimensional space and let   $$Q(C) = \underset{C}{\int\!\!\dotsb\!\!\int} dx_1 dx_2 \dotsc dx_n.$$  If $C = \{(x_1, x_2, \dotsc, x_n) : 0 \le x_1 \le x_2 \le \dotsb \le x_n \le 1  \}$, then   $$Q(C) = {\int_0^1 \int_0^{x_n} \dotsb \int_0^{x_3} \int_0^{x_2}} dx_1 dx_2 \dotsc dx_n = \frac{1}{n!}.$$


C# String and string. Why is Visual Studio treating them differently?

If I create a normal Console App with a normal Main entry point as follows  using System;  namespace ConsoleApp {     public class Program     {         public static void Main(string[] args)         {             // do stuff         }     } }   then select it in visual studio everything is fine..    However, if I write the code as follows...  using System;  namespace ConsoleApp {     public class Program     {         public static void Main(String[] args)         {             // note the capital S in String         }     } }   then everything is not fine....    Does anyone know why is it not picking up the String[] but happy with the string[] please ?  edit: Extracting from comments, it appears to be a bug in Visual Studio 2012 and 2013. Presumably it's also present in earlier editions but appears to have been rectified in VS2015. It's not a problem per se, and as noted the code still compiles and executes with either string[] or String[] I'd be interested to know the cause of the bug in VS though. I'd imagine the property editor window isn't Using System; ?


I can do an eval("something()"); to execute the code dynamically in JavaScript. Is there a way for me to do the same thing in C#?  An example of what I am trying to do is: I have an integer variable (say i) and I have multiple properties by the names: "Property1", "Property2", "Property3", etc. Now, I want to perform some operations on the " Propertyi " property depending on the value of i.   This is really simple with Javascript. Is there any way to do this with C#?


Leibniz test $\sum\limits_{n=1}^\infty \sin\left(\pi \sqrt{n^2+\alpha}\right)$

I am given a series: $$\sum\limits_{n=1}^\infty \sin\left(\pi \sqrt{n^2+\alpha}\right)$$ And in the description of the problem it is said that I must show by Leibniz test that it is convergent. How can I even get the $(-1)^n$ symbol out of the starting series?


What preposition is best in this sentence?            I would rather you arrived on time to school.       I would rather you arrived on time for school.


Rich snippet rating and review data not showing on Google SRP

Searching Google for for  returns no reviews data for my website even through I have correct review markup.   Is it an error in page tagging or just a matter of time before Google discovers the mark and then displays the review ratings?


can 3 2x6 x8' wooden board support a 900lb load?

I wish to support a 900 lb motor I want to use 3 2x6x8 for a support beam will this be enough?


Count of reputation updates without refreshing the page but hover still have the old value.


Ubuntu 17.10 crashed. How can I recover the lost files?

I had trouble installing virtualbox for ubuntu 17.10. To run it properly I needed to configure dpkg and when I restarted the system it showed some lines of code like "failed to load resource and the platform". I know how to install ubuntu again, because the first time I did with an USB and this time I'll do the same, but the problem is: How can I recover my files? Thanks!


Is this PHP code vulnerable to SQL injection?

I have a website where I use PHP in server side and mysql as database. I use the following script to retrieve data from database. Could anybody let me know whether this code is vulnerable to injection attack? If so could you please give a solution?  <?php // PHP script   $usrname=$_POST['usrname']; $_SESSION['usremail']=$usrname; $usrpassword=$_POST['passwd'];  $db=mysql_select_db('mydb',$connection); $result=mysql_query("select usrfname,usrlname from userinformation where usremail='$usrname' and usrpassword='$usrpassword'") or die('failed to login');   Any help is greatly appreciated.  Thanks


Does $S(n)$ contain infinite many primes?

Denote $p_j := j\text{th prime}$ and $S(n)\:=\sum_{j=1}^n p_j$ (The sum of the first $n$ primes).     Is it known whether $S(n)$ is prime for infinite many $n$?   OEIS gives the sum of the prime numbers  upto $10^{18}$, which is $12,212,914,292,949,226,570,880,576,733,896,687$, being a $35$-digit prime.  The relative low growth rate of $S(n)$ (of order $n^2\ln n$) is another heuristic argument that the answer to the given question should be yes.


private List<Manufacturer> productManufacturer = new LinkedList<Manufacturer>();  I am not able to understand why <> this symbol is here and Manufacturer inside it to define a LinkedList in Java.


Let's say I run this command:  from pyspark.sql.types import *  How can I check all the names that have been imported into my namespace? For instance, IntegerType() is now available, but is there a programmatic way of seeing all the names that have been imported with the *?   Note that I am not just looking for functions, but all names (including attributes) etc.  Thanks


Make mouse movements scroll when the middle button is held down

In Windows, I'm used to clicking the center button and it offering a "fast scroll" option up or down. How can I get this behavior on Linux? It currently seems to use the back button upon center click instead.  I use Gnome under CentOS.


How to read one filesystem from a whole disk image file?

I ran these commands:  VBoxManage clonehd d6b9f0a5-98df-48ca-83c8-91a0809ec349 --format RAW Debian.raw sudo dd if=~/.VirtualBox/HardDisks/Debian.raw of=/dev/sda5   When I try to mount the partition, I get this complaint:  EXT4-fs (sda5): VFS: Can't find ext4 filesystem   Now I know that the VM had an ext4 partition. What did I do wrong?


If a finite set $G$ is closed under an associative product and both cancellation laws hold, then it is a group

Problem  Suppose a finite set $G$ is closed under an associative product and that both cancellation law hold in $G$. Prove that $G$ must be a group. Also show by an example that if one just assumed one of the cancellation laws holds, then the conclusion need not follow.  This is from Topics in Algebra by Herstein Specific question How can I prove the properties of group from the both cancellation laws? In short, the identity and invertibility. If $a$ and $b$ belong to $G$ then $ab$ belongs to $G$ (closure property), but does it imply that  it has an identity element.


I have a question concerning the creation of rings in the Lord of the Rings. It's, at least, hinted that the reason the Elves depart for Valinor after the demise of Sauron is because their Rings lose their power of preservation, hence the enchantments on Lothlorien would eventually wane, making it less like Valinor. But why can't they create more? Lets look at the Facts:  Fact 1 : We know that Celebrimbor is the only Elf that can forge the rings since Sauron under the guise of Annatar taught him how to. We also know that Celebrimbor was killed by Sauron before he could reveal this knowledge. However, Elves can't truly die until the end of the world and are lingering about in Valinor and I am sure that's where Celebrimbor is.  Fact 2: We know that Elves can go to Valinor and come back to Middle-earth since the Noldor have done precisely this.   So my question is, Why can't an Elf go to Valinor, learn the secret of forging rings from Celebrimbor, come back to Middle-earth and forge new ones?  Some are suggesting this question is a duplicate but I don't see how. I am suggesting a possibility where an opportunity was indeed present. Answers such as the elves fearing the past does not seem too convincing to me, after all it was a Maiar that got corrupted not the ring wearing elves. Why would they doubt themselves?


Can two lasers produce light which is coherent. Are the light have same frequency and wavelength


I have been learning CPP lately, and I came across this question: Consider the below program: #include <iostream> using namespace std; class Hall {  public:  double cost; }; int main() {  Hall hall;  hall.cost=10000.50;  cout<<hall.cost;  return 0; } What will be the output of above coding?   The answer to this question is 10000.5, however, I couldn't understand why is it so ? In my opinion, answer should be either 10000.500000 as double has precision upto  6 decimal digits or it should print 10000.50 as it is the value assigned to hall.cost. Please explain.


I have a question with a query in PostGIS. I try to calculate the area from a polygon. It actually works but the area-result is not correct. My Query is:  SELECT name, ST_Area(way)/10000 AS hectares FROM osm_data ORDER BY hectares DESC LIMIT 1;   The problem is, that the amount of ha is completely wrong. So i tryed to change the EPSG in the standard 4326 EPSG. But when I use than the query it shows me an error:  SELECT name,ST_Transform ((way, 4326)ST_Area(way))/10000 AS hectares FROM planet_osm_polygon ORDER BY hectares DESC LIMIT 1;      SQL state: 42601   Where is the mistake?!


Is $A^2$ is diagonalizable , then is $A$ diagonalizable when $A$ is non-singular?

I have a question in mind which is a slight generalization of a past question(famous). See here  if you want the basic version. Now my question : If $A^2$ is diagonalizable , then is $A$ diagonalizable when $A$ is non-singular? Obviously, the previous counterexample of taking $A$ to be a nilpotent matrix of index will not work here as then $|A|=0$. Any proofs?


Is the Sun losing mass and pushing the Earth further away?

With the sun radiating so much energy every millisecond can nuclear fusion keep up with that pace? And if it can’t keep up isn’t the sun losing energy every second and therefor losing mass? Which leads to a smaller curvature of space time around it and therefor pushing the earth further away. And if this is true, isn’t this a huge problem? Or are the effects so small that it won’t be a problem until millions of years?


I am having difficulties understanig inheritance in Python, but I have an idea how it works because of my somewhat larger experience in Java... To be clear, I searched the questiones here as well as online documentation, so I am aware this will be branded as repeated question in an instant :P  My code on Codecademy passes like this:  class Car(object):     condition = "new"     def __init__(self, model, color, mpg):         self.model = model         self.color = color         self.mpg   = mpg      def display_car(self):         return "This is a %s %s with %s MPG." % (self.color, self.model, self.mpg)      def drive_car(self):         self.condition = "used"  class ElectricCar(Car):     def __init__(self, model, color, mpg, battery_type):         self.model = model         self.color = color         self.mpg   = mpg         self.battery_type = battery_type   But as far as I can see, I'm almost defining a new class... Where is the inheritance in that? Could I do something like:  class ElectricCar(Car):     def __init__(self, battery_type):         self.model = model         self.color = color         self.mpg   = mpg         self.battery_type = battery_type   Maybe something with a keyword  super   ?


Controlling frame number and background behaviour from a template

I have implemented my university's PowerPoint templates in Beamer, and have run into a corner issue regarding page numbers. So far, I have opted for the straightforward solution, that is, checking if a slide is the first, and not printing the page number if it is.  However, some would like to have presentations without title pages, and then the page number should be shown nonetheless. Also, if the title page comes later, it should not have a page number. I have solved that issue with a workaround: A specific titlepage command that sets footline and background beamertemplates locally. However, it is not entirely satisfactory, since I don't think the end user should have to know such commands.  The current code is available at    Most of you will probably know that the reason this is difficult is because the footline and background templates are called before beamer can know whether it will be a title page or not.   I'm looking for ideas to make the placement of the title page completely flexible. Since I haven't made a MWE for this, I will be perfectly happy to do the details of suggested workarounds myself, and report back with a completed solution.  My only criterion is that it should only require standard elements for the end user, whereas my own code in the sty files perfectly well can contain ugly hacks.


Kinetic energy is simple, right?! from the equation it seems as though if you know the speed and mass you'll know the work. Let's try to prove it. let's assume we know the acceleration and distance for now. $$w=mda$$ So the distance is $$d= 1/2 *at^2$$ Then  $$t = \sqrt{2d/a}$$ So $a*t$, which is the speed, is  $$a*\sqrt{2d/a} = a* \sqrt{2d}/\sqrt{a} = \sqrt{2da} = \sqrt{2w/m}$$ So regardless of the distance or acceleration, if you know the work and the mass, you can calculate the speed which is  $$v=\sqrt{2w/m}$$  What if you know the speed and the mass? You can easily calculate the work. $$v = \sqrt{2w/m}$$ Then  $$v^2 = 2w/m$$  That would mean  $$m*1/2*v^2=W $$ Rearrange it and  $$W= 1/2 *m *v^2$$ would be the equation.  What if you have an initial speed and a new speed and want calculate the amount of work done after an initial speed to get the new speed? You'll just subtract the total work from the initial speeds work.  $$1/2mv^2 - 1/2ms^2$$  where s is  the initial speed and v is the new speed. However if you do it the other way which is  $$d= 1/2at^2 + vt$$ and solve it the answer would be $$1/2ms^2  + 1/2msv$$ Why aren't they equal?


how to keep Smooth mode from making ripples?

The smooth shading mode is nice, but often times it seems to leave ugly marks where edges are. it doesn't do that between every face, but it does for some faces. I tried flipping normals but all that does is make it lighter or darker, but doesn't actually smooth it out. I tried making all the faces merged, but that didn't help.


How can i create the shader of the virus?

I've been trying, but my result is not convincing at all  here it is: (Note that the model is missing a subsurf)   here the node setup   Thank you


I just install Ubuntu. One of the things I miss about windows is the lack of executable.   When I right click the .sh file, go to permissions, and check "Allow executing as a program", it never does execute as a program when I double click it.   Another solution I found is doing it in the terminal. This doesn't work either.    What am I doing wrong? Is this really too stupid of a question or am I too stupid? Thanks for any help!


symmetric marginal but asymmetric joint distribution contours

Let us say we have two continuous random variables, $X$ and $Y$ such that their pdfs $f(x)= f(-x)$ and $g(y)= g(-y)$ for all $x$ and $y$. In other words, $X$ and $Y$ have symmetric distributions around 0. Is it possible that joint distribution of $X$ and $Y$ will be such that $f_{joint}(x, y)$ is not always equal to $f_{joint}(-x, -y)$ for all $x$ and $y$? Please provide proof or simple counterexamples, if possible.


Producing Lines of Text without underfull \hbox errors

I'm preparing a colophon for a book I'm writing in memoir class. The code is as follows:  \documentclass{memoir} \usepackage{lipsum} \usepackage{nth} \usepackage{textcomp} \usepackage{multicol}  \setlength\parindent{0pt} \setlength\parskip{5pt}  \begin{document}  \thispagestyle{empty}  ~\vfill  \textbf{My Awesome Book}, \textsc{\nth{3} Edition} \\ Copyright \textcopyright{} \the\year{} John Doe.\\ Some Rights Reserved.\\ Last edited: \today.\\  \begin{multicols}{2}     Some Text\\     More Text\\      \footnotesize     \lipsum[1-4] \end{multicols}  \clearpage  \end{document}   Which produces the following output (excerpted):    Everything looks as it should. There's just one problem: compiling this code (with lualatex, incidentally), gives the following warnings:  Underfull \hbox (badness 10000) in paragraph at lines 16--20   Underfull \hbox (badness 10000) in paragraph at lines 22--24   These warnings disappear when the line breaks \\ are removed. Is there anyway to accomplish what I'm trying to do without producing these warnings? Furthermore, is there a more "correct" way to have lines of text which aren't organized into paragraphs?


Having an issue with simple account checking program? Program returns compiling error that states "no match for 'operator||' unsure of how to fix?"

I'm new to programming and so I bought a book to help me learn C++, in the book it asks me to do a practice assignment where I must create a program that allows me to take input of multiple usernames and passwords, match them, and also allow someone who incorrectly enters information to try entering it again. I've wrote the following program in order to do so. If anyone can also shed any light on how to make the program allow for retry of username/password entry without ending the program that would also be greatly appreciated. Thank you!  #include <iostream> #include <string> using namespace std;  int main() { string username1="Varun"; string username2="Agne"; string username3="Geetha";              string username4="Mohan"; //Usernames for accounts string pass1="PassworD"; string pass2="PASSWORD"; //Passwords for accounts string pass3="password"; string pass4="Password"; string Uattempt; //User input for username string Pattempt; //User input for password   cout << "Please enter your username.\n"; cin >> Uattempt; cout << "Please enter your password \n";   //Asks for username and password entry by user cin >> Pattempt;  if(Uattempt!=username1 || username2 || username3 || username4) {     cout << "Access Denied. Incorrect username or password. Please retry.\n";  //If username does not match possible entries, program will ask to retry } if(Pattempt !=(pass1||pass2)&&(pass3||pass4) {     cout << "Access Denied. Incorrect username or password. Please retry.\n";  //If password does not match possible entries, program will ask to retry } if (Uattempt&&Pattempt==username1&&pass1||username2&&pass2||username3&&pass3||username4&&pass4) {     cout << "Access Granted. Welcome " + <<Uattempt<< + ".\n"; } else {     return 0; } }


I try to find the question but I didn't   How do you do it? I'm really stuck on this proof. Can someone please explain?


What are the rules when you use the conjunction "and"?

I'm actually quite confused. Let's see...  I have eaten and drunk.  Or  I have eaten and have drunk.  I know the first one sounds... well, I think it sounds right, but...   Another one-  Azel is growing up and eating more.  Or  Azel is growing up and is eating more.  How do you know when to repeat the conjunction "and"?


If $f$ is continuous real function such that $f(11) = 10$ and $\forall x, f(x)f(f(x)) = 1$ then find $f(9)$

If $f$ is continuous real function such that $f(11) = 10$ and $\forall x, f(x)f(f(x)) = 1$, then $f(9) =$ ?


Salesforce Internal Error: HAPPY.CMETAACCESS

We have created our own 2nd generation package and trying to install it in our org, but getting the following error: 1.  ORA-20001:  ORA-06512: at "HAPPY.CMETAACCESS", line 665 ORA-01403: no data found ORA-06512: at "HAPPY.CMETAACCESS", line 848 ORA-06512: at "HAPPY.CMETAACCESS", line 799 ORA-06512: at "HAPPY.CMETAACCESS", line 784 ORA-06512: at "HAPPY.SITEDEVCOMPONENT", line 718 ORA-06512: at line 1   {call SiteDevComponent.load_sitecomponents(?,?,?,?)} : ORA-20001:  ORA-06512: at "HAPPY.CMETAACCESS", line 665 ORA-01403: no data found ORA-06512: at "HAPPY.CMETAACCESS", line 848 ORA-06512: at "HAPPY.CMETAACCESS", line 799 ORA-06512: at "HAPPY.CMETAACCESS", line 784 ORA-06512: at "HAPPY.SITEDEVCOMPONENT", line 718 ORA-06512: at line 1   {call SiteDevComponent.load_sitecomponents(?,?,?,?)}  Has anyone encountered something like this before? Any tips would be helpful around the potential causes based on Oracle errors.


I'm having a frustrating time on the red lava level in the sewers on Fez. It may be that my platforming skills are not up to par, but are there any suggestions as to how to get through it easier?


How do I add null to a List of generic type?

I am trying to do this: protected List<T> list = new List<T>();  for (int i = 0; i < size; i++) {     list.Add(null); }  I get a compiler error saying "cannot convert from null to T". I have looked around but could not find an answer to this question.


Why does Lualatex crash after a recent update?

After updating packages of MiKTEX 2.9 lualatex stopped working.  I execute this code:  \documentclass[12pt]{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} \node[] at (0,0) {A}; \end{tikzpicture} \end{document}   and I get this error:  "Process started: lualatex.exe -synctex=1 -interaction=nonstopmode "test".tex Error: Command crashed: lualatex.exe -synctex=1 -interaction=nonstopmode "test".tex Process exited with error(s)"   Why does the command crash? What should be done to continue my work?   PDFLatex and XeLatex work fine, but I need lualatex, cause my thesis is with lualatex.


Multiple bibliographies with BibTeX and IEEEtran: error with citations INSIDE captions

I am writing my PhD thesis and I am using an adapted version of the memoir-class + IEEEtran.bst for the bibliography style.   The idea is to create a specific List of Publications exclusively with the papers of the PhD canditate. This List of Publications is divided in two sections:'pub' denoting peer-reviewed papers, and 'pubOther' for other publications. Inside the document, the command \selfcite{} is used for citations in aforementioned List of Publications.  I get errors if I use \selfcite{} INSIDE a caption, while everything works fine if it is used elsewhere.  Here I copy the error I get:  ! Undefined control sequence. <argument> ...@tempc }\fi \fi \def \@tempa {\@nil }\ifx \@tempa \@nnil \else... l.96 ...ncies. (Source: \selfcite{JS2009})} ?   While here I copy the piece of code describing the List of Publications and the command \selfcite  \RequirePackage[resetlabels]{multibib}  % Used for multiple bibliographies, as this class enables the use of a separate List of Publications      %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % We define two 'sections' in our own List of Publications, but it can be     % % expanded as desired. Here, 'pub' denotes peer-reviewed papers (journals,    % % conferences), and 'pubOther' denote other publications (popular article,    % % invited talk, workshop, ...). Use \selfcite{<key>} to cite these            % % These two lists need to be separately compiled: 'bibtex pub'                % %                                                 'bibtex pubOther'           % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \makeatletter \newcites{pub}{Peer-reviewed} \newcites{pubOther}{Other} \newcommand\biblabelprefix{} \newdimen\b@belwidth \newdimen\b@b@lwidth \newcommand\setbabelwidth[1]{{%     \newbox\tmp     \setbox\tmp=\hbox{#1}%     \global\b@belwidth=\wd\tmp }} \renewcommand\@biblabel[1]{{%     \newbox\tmp     \setbox\tmp=\hbox{#1}%     \@tempdima=\wd\tmp%     \@tempdimb=\m@ne\@tempdima     \advance\@tempdimb by \b@belwidth     \rule{\@tempdimb}{0pt}[\biblabelprefix#1]% }} \def\@bibitem#1{%     \item\if@filesw         \immediate\write\@auxout{\string\bibcite{#1}{\biblabelprefix\the\value{\@listctr}}}%     \fi\ignorespaces} \renewcommand{\@fnsymbol}[1]{%     \ensuremath{%         \ifcase#1\or \dagger\or \ddagger\or         \mathsection\or \|\or \mathparagraph\or **\or \dagger\dagger         \or \ddagger\ddagger \else\@ctrerr\fi     } } \newcommand\blfootnote[1]{% Enable a footnote at begin of chapter to say e.g. parts of this chapter were published in ...      \xdef\@thefnmark{\null}     \@footnotetext{%     \hspace{-1.8em}     #1     } } \@ifundefined{@mb@citenamelist}{\def\@mb@citenamelist{cite,citep,citet,citealp,citealt}}{\relax} \def\selfcite#1{\setcitestyle{open={[\initials}}\citepub{#1}\setcitestyle{open={[}}}  \newcommand\listofpublications{{%     \small     \setbabelwidth{10}     \microtypesetup{protrusion=false}%       \renewcommand{\bibsection}{%no chapter but simply section         \section{\bibname}         \prebibhook     }        \renewcommand{\biblabelprefix}{\initials}% Add prefix to biblabel for publications     \continuouslabelstrue     \bibliographystylepub{IEEEtran2}%     \bibliographystylepubOther{IEEEtran2}%     \chapter{List of publications}     \scriptsize      \bibliographypub{IEEEabrv,\bibfile}     \bibliographypubOther{IEEEabrv,\bibfile}%        \microtypesetup{protrusion=true}% }} \makeatother   Can you please help me to find the problem? Thanks!


Why is the light in an airplane turned off during take off and landing?

I wondered for a long time why the light inside an aircraft is always turned off when taking off or landing.


I can't think of the word that describes a word snob and use of the word pretty much proves you are one.  Anybody?


Which one should be used?      To me, it makes no difference, but I'm not really sure why.   vs     For me, it makes no difference, but I'm not really sure why.


is there any way to secure your whole code ? or some important files. which is not changeable to other even it is deployed to other servers like client's server.  or we can create any DLL file(which is not changeable) which can be run by Apache server and authenticate the requirements.


Ordinarily I draw graphs in tikz with:  \begin{tikzpicture}     \Vertex[x=1,y=1]{x1}     \Vertex[x=2,y=1]{x2}     \Vertex[x=3,y=1]{x3}     \Vertex[x=4,y=1]{x4}     \Vertex[x=5,y=1]{x5}     \Edge(x1)(x2)     \Edge(x2)(x3)     \Edge(x3)(x4)     \Edge(x4)(x5) \end{tikzpicture}   Now I want to draw a factor graph, where the vertices are squares instead of circles.  This is the only difference.  I can't, however, find out how.  How do I?


My US visa  b1/b2 got rejected for the second time under 214 (b). I hold Indian passport, living in KSA for 3 years as resident (Doctor). Since i want to attend a conference in US which will be held in every year in any one of the states , i decided to attended interview in KSA and was rejected. can you please suggest what could be the possibilities  and how i can improve my chances  for next time? how long I should wait before applying for a next chance?   Both interview, I was prepared with invitation letter from organizers of conference, salary certificate from employer, evidence of family ties in KSA, asset documents. Unfortunately consul officer not asked for any of documents and he clearly told that he need only the passport when I tried to give all the documents.  First interview was:   me- good morning officer: good morning me: when i was trying to submit passport and other documents  officer : give only your passport officer: first time to us? me : yes officer : why you are going to us ? me : to attend conference  officer : who sponsoring? me : myself officer: what your job in ksa, how long, salary? me; bla..bla..bla  officer : are you traveling alone ? me : yes officer:are you married?  me : yes, staying here with family  in KSA, have 2 kids. officer:have you traveled to any other country during last 5 years? me : UAE once officer: relative in us ? me : no officer: any relative in canada ? me: no officer: show your bank statement? me : shown officer: cannot issue a visa under 214(b).   Since conference is hardly 2 weeks away, Second attempt was done exactly a week later after submitting a new application. This time I included more documents to prove more ties such as family photo with date,  my first kid's school fee receipts, bonafide  certificate from school , second child's vaccination card, my car documents etc..and all documents organized well. on the day of second interview :  me : good morning ( same officer interviewed for the first time ) officer: good morning me : i was trying to give all documents including passport on top in a transparent file. officer: give only the passport officer: travelling first  time to us ? me : yes officer: purpose?  me ; to attend conference officer:you have been here before? smiling me : yes, last week officer : give your token number, you have to wait  wait until Some one calls you. after a minute i was called for interview by  another officer. officer 2 : hi good morning me : good morning officer 2 : what you doing here me : im working as bla bla  officer 2 : how long in KSA  me:3 YEARS officer 2 : WHERE YOU GOING TO US ? ME :  bla bla to attent conference officer 2 : your salary me : bla bla officer 2 : travelling alone me : yes officer 2 : dates of your conference? me : bla bla officer 2 : have you traveled TO ANY COUNTRY DURING PAST 5 YEARS ? ME : UAE  officer 2 : with in  past 3 years have you traveled to any country other than India ? me : no officer 2 :  sorry, your visa got denied under section 214(b).   Both officers not asked for any other documents/ ties  and so i didn't gt  a chance to show/ explain the ties.  what could be the possible reason for rejection? how can i improve my chance if iam applying for nex time either for conference / for sight seing with my family ?


I have a dictionary, the keys are integer values and the values are a list of strings. I want to make it vice versa, the string become key and integers become values.  Like:  first design:  {1:["a"], 2:["a","b"], 3:["a"], 4:["b", "cd"], 6:["a","cd"]}   second design:  {"a": [1,2,3,6], "b":[2,4], "cd":[4,6]}   any clue? Thanks


Existence of totally ordered ring with zero divisors

Does there exist a totally ordered ring with zero divisors? I can't think of an example right now.


How would you explain these mistakes to an adult language learner?

what is the mistake in "I Have visited washington two years ago"?


derivative of $e^x$ using the limit definition

Looking to prove  $ f(x) = e^x =f'(x) $ using the limit definition of the derivative. So far I have gotten to here:  $e^x * \lim\limits_{h \to 0} \frac{e^h-1}{h}$  Any hints on what I can do next to get that entire limit to $1$?  I can't use l'hopital's rule, otherwise that'd defeat the purpose.


just had a quick question.  Should be a simple fix.  When I am trying to bring in HDRs for lighting, it seems to not be scaling or working properly.  I can't see the HDR in the background.  I have kind of fiddled around with it by trying to use texture coordinate and mapping in the world section of the node editor but nothing was working.  It appears that the HDR is still lighting my scene for the most part but it's all thrown off.  Here is a screenshot of what it looks like.  You'll notice there is some blue in the background, but that's not very helpful.  Also, you can see what the HDR looks like in the preview area on the properties editor.  Thanks for the help!


$(-1)^{1/3} = ((-1)^2)^{2/6} = 1^{2/6} = 1$  but the actual answer is (-1)  what is wrong with the first approach?


Paperback novel: Earth hits cosmic string, human DNA affected, main character is a White Card - Protoman

I read this in the late 80's early 90's as a long paperback novel. The earth hits a cosmic string, humans DNA is damaged. The main character is a "White Card" his DNA is pure. He is a slave/worker for someone who recognizes that he is a white card and is trying to make him into a "Protoman". He kills the guy and tangles his body in a fishing net to give the appearance that it was an accident. He escapes. The rest I don't remember much.


Identify cartoon about a set of fairy/demon twins in a far future where the demon uses propaganda to take over the world

I'm looking for a cartoon from the 70's (I believe) which is about a set of twins; one plump "fairy" and a skeletal "demon". The "fairy" has magic powers and ends up living a life of pleasure, while the "demon" flees and turns evil.  When the "demon" finds his new weapon in the ruins of the ancient world (roughly modern day) he plots to enslave the world; the weapon in question is a set of propaganda movies with Adolf Hitler.


Can I turn off high-DPI scaling for all applications?

I'm on a Windows 8.1 laptop (Thinkpad T440s). For some programs to not appear blurred/scaled, I have to access the .exe properties, go to Compatibility and "Disable display scaling on high DPI settings."  This is pretty annoying to have to do for many applications, and whenever I install a new program. Is there a global override I can use?


Changing the color of itemize item in beamer

I would like to change the color of itemize item and itemize subitem (the bullet) throughout the presentation. I was wondering how I can do that. Here is my MWE:  \documentclass [11 pt, xcolor=pdftex,x11names,table]{beamer}  \usepackage{pgf, pgfpages} \usepackage[latin1]{inputenc}  \usepackage[english]{babel} \usepackage{beamerhighlight} \usepackage{colortbl} \usepackage{color} \usepackage{pdfpages} \usepackage[absolute,overlay]{textpos} \usepackage{url} \usepackage{graphicx}  \mode<presentation> {     \usetheme{Madrid}     \usefonttheme{professionalfonts}      \setbeamertemplate{itemize item}{$\blacksquare$}     \setbeamertemplate{itemize subitem}{$\blacktriangleright$} } \usepackage{hyperref} \begin{document} \begin{frame} \begin{itemize}     \item hey \end{itemize} \end{frame} \end {document}