Interval of existence of a certain first-order ODE

Without solving the following initial value problem, determine the interval in which the solution is certain to exist: $$\dfrac{dy}{dx}+(\tan x)y=\sin x, \ \ \ y \left (\frac{\pi}{4} \right )=0.$$   Please help me also solve (if you can) under what conditions the solution of the first-order ordinary differential equation exists?  This question is different is differenr from the previously asked queston in a way that it has two parts furthermore, the equation given is completely different from the previously asked question.  It is sad that none of the repliers have answered the question yet whereas they have accepted that they know answers. I am extremely disappointed with this forum which was suggested to me by my friend. Leaving it right now. Good Bye.


I already record my biometric , should I record biometric for my new visa?

I am going to UK for business trip and may apply 6 month business trip visa. Should I record my biometric for second time even though I have already recorded my biometric last year?  Indonesian, female, 28 years.


Automatically create and remove desktop shortcut to USB device?

Is any possible to have:    When I plug in a USB drive, a shortcut to it is created on the desktop automatically? When I unplug in a USB drive, the shortcut to it is removed from the desktop automatically?


Can I use a single jumper wire to run to two outlets and two breakers?

Situation: Have a jetted bathtub that requires 2 15A gfci outlets each to its own breaker. Problem only have one wire running into tub area (would have to tear up.newly installed floor to run another. Is it possible to use that single wire and connect two wires and run to the outlets and connect two wires to the other end of the wire (wire is approx 8 ft) and run those to the breaker box and attach to two gcfi breakers?


How to place two pictures next to each other?

I added two photos in Latex. I want these two pictures to be placed next to each other. Note that two pictures are appropriate, not two sub-pictures in one picture. \begin{figure}[t]     \centering     \includegraphics[width=\linewidth]{figure/a.eps}     \caption{This is my first picture } \end{figure}  \begin{figure}[t]     \centering     \includegraphics[width=\linewidth]{figure/b.eps}     \caption{This is my second picture. } \end{figure}


Prove that $\det A=0$ if $I \notin \operatorname{span} \{A,A^2,\dots,A^n\}$

Why if $A \in \textsf{M}_{n\times n}(F)$ and  $$I \notin \operatorname{span} \{A,A^2,\dots,A^n\}$$  so $\det (A)=0$?  I understand that $A$ is not invertible if $I \notin \operatorname{span} \{A,A^2,\dots,A^n\}$, but can't explain why.


I installed Ubuntu 16.05 alongside Windows 10 on a Dell Inspiron 3543 laptop. Installation was successful, but could not get the WiFi connected to the internet.  I can see my SSID being displayed on the drop down menu, but WiFi doesn't work after I click it and enter the WiFi password. The WiFi icon is displayed with an "empty WiFi" sign.    How can I fix this so that I can access the internet?  I followed instruction from the duplicate page step by step and still have the issue.


I'm trying to match Cycles to a Blender-Internal material setup and I didn't see a way for cycles to have an image reference more then one UV map.  Is it possible to have a node setup with 2 image textures, each using a different mesh UVLayer?


Is it possible to calculate the average value of $x^{2}p^{2}$ for an infinite square well?

If you can only measure either position and momentum in quantum mechanics how would one find the average value of $x^{2}p^{2}$ for an infinite square well?


Problem in second and third author using Biblatex

My code:  \usepackage[backend=biber, style=authoryear, citestyle=authoryear, dashed=false,maxcitenames=2,giveninits]{biblatex} \renewcommand*{\nameyeardelim}{\addcomma\space} \DeclareNameAlias{editor}{last-first}  \DeclareNameAlias{translator}{last-first}   and referencing:  @inproceedings{kazem2003design,   title={Design considerations for a background auditory display to aid pilot situation awareness},   author={Kazem, Mandana LN and Noyes, Janet M and Lieven, Nicholas J},   year={2003},   organization={Georgia Institute of Technology} }   The outcome:    It supposes to be:  Kazem, M.L., Noyes, J.M. and Lieven, N.J., 2003. Design considerations for a background auditory display to aid pilot situation awareness. Georgia Institute of Technology.   where the order of the first name and last name for the second author and the third author is not working well.   (Second author) J. M. Noyes --> Noyes, J.M. (Third authro) N.J. Lieven --> Lieven, N.J.


I do not have anything other than the normal using System;  namespace TryStuff {     class Program     {         static void Main(string[] args)         {                      }     } }  And I know that having nothing at the start and still asking questions isnt highly looked on but STILL... Im trying to create a code that asks you for an integer, and if you answer anything over 0, it ADDS the given number to an array, once you stop giving numbers (example type some "stop") it prints out ALL the numbers given to the array. I DO NOT need the full code for something like this, just an answer to how do I append to an array without making it insanely complicated (things ive found on the google are like 20 lines of code but im pretty sure its not that hard). Sorry for the long post and in short, how do I append to an array? If you can provide me a code, please implement it in the C# code or give me a "explanation" how to do it. Thank you very much!


OS-Prober doesn't show my Windows 7 partition

I'm having a problem installing Ubuntu 12.04 on my ASUS UX31A alongside Windows 7; I tried to launch os-prober in my terminal and the only option I get is:   /dev/sda5:Windows Recovery Environment (loader):Windows1:chain   while Windows 7 (mounted on dev/sda3) is not shown.  This is what I see in my Disk Manager in Windows 7:    C: basically is the partition with Windows system's file, while the D: one is for data), while this is what I see when I launch GParted:     May it be because Windows is installed on SSD? How do I know that? Is it safe if I proceed with the installation for computers with UEFI, SSD and HDD? I'm not sure that's my case.


Private Beta link on the help > asking page

I was perusing the  of GIS to make sure that my next question is on-topic for their site and I noticed something that was rather odd for a graduated site, a link that says        it appears that this is on other Help Pages as well, Meta being one of them.  Is there a reason why this is kept linked? Note that this is not a duplicate of  asking for it to be removed.


Install the correct Nvidia driver version for NVIDIA CUDA Toolkit

I have installed Ubuntu on, but now I am trying to install NVIDIA CUDA Toolkit for the GPU. When I install it, it says that there is no driver found, so I have tried to install the driver, but I don't know why after installation, the system not coming up. Maybe it is because of the wrong version of the driver.   When I tried to detect the driver version using sudo lshw -C display , it showed this information:    But here it doesn't say that what is the product name of the driver, and also when I go Software & Updates -> Additional Drivers, then it says NVIDIA Corporation: Unknown.    What should I do?


I found  on Stack Overflow.  Whoever created or edited the tag had said specifically not to use it. What is the point of the tag then?  It has quite a few questions on it, which some are very well  received. Should we delete this tag?  I asked this question on Meta because there might be similar tags on other Stack Exchange sites.


Let it be more clear for new users that their questions can be edited anytime

After  on a  from a new user,  was:     thanks for the corrective feedback, as this is my first question ever   on Stackoverflow. Didn't even know I could edit the question again,   which I will based on your advices. If you can, please tell me if my   new question is more appropriate. Thanks. – Filipe Santos 9 mins ago   By this comment, the new user didn't know about editing their question.  Hence, this might be use for future modifications of the help page and related material first shown to new users.  Is there plan(s) to handle the correct or more direct tutorial/information/guide to new users?     doesn't answer this question - it only saw comment and say the OP about edit their own answer instead using comments - which is not what my question is about. My point was some like the question-wizard and there it's explained that they can edit ther question anytime.


Why are no Pokemon are spawning at my house?

I keep my phone on for hours, even though there are Pokemon nearby they never come over my house so I can never catch them.


How to find which item in a JSON list has the greatest value for a given attribute in Python?

I'm using JSON data from the .  What I need to do is to find the most recent goal scored by a given team in a given match. To do that, I need to sort by the value of the attribute key in each element of the array that is the attribute of the away_team_events attribute.   Let me illustrate.   Here's sample JSON for France from the ongoing (at the time of writing) France v Switzerland.  "away_team_events": [             {                 "id": 276,                  "type_of_event": "goal",                  "player": "Giroud",                  "time": "17"             },              {                 "id": 277,                  "type_of_event": "goal",                  "player": "Matuidi",                  "time": "18"             },              {                 "id": 278,                  "type_of_event": "penalty-wrong",                  "player": "Benzema",                  "time": "32"             },              {                 "id": 279,                  "type_of_event": "goal",                  "player": "Valbuena",                  "time": "40"             },              {                 "id": 281,                  "type_of_event": "substitution-in",                  "player": "Pogba",                  "time": "63"             },              {                 "id": 282,                  "type_of_event": "substitution-in",                  "player": "Koscielny",                  "time": "66"             },              {                 "id": 283,                  "type_of_event": "goal",                  "player": "Benzema",                  "time": "67"             }         ]   So what I need to do here is find which "id" attribute is greatest, because that will be the latest goal.   How do I sort by a specific attribute like this?  I've seen , but I can't really make sense of the answers.  EDIT: rephrase, sorry for the confusion.   I don't need to necessarily rearrange them, but how do I identify which item in the list has the greatest id, and use that?


Post viral apocalypse story, maybe from 50's, hero was bitten by a rattlesnake, has hammer

I read an already old paperback novel in about 1969. Most human life is destroyed by a virus, and it is the story of one of the survivors.  I remember:  he survives because he had just been bitten by a rattlesnake and  as he finds other survivors his hammer becomes the symbol of authority.  There is a late scene when only his young son or protégé is willing to pick up the hammer.   It may have been called something like 'The Green Earth', 'The Good Earth', titles which do not do well on a Google search.  My impression at the time was that the author was not a regular sci fi writer, but I don't know for sure.


Is there a keyboard shortcut for maximizing the current window on Lubuntu 16.04?


Is frequency quantized in the black body spectrum?

I'm aware that there're some questions posted here with respect to this subject on this site, but I still want to make sure, is frequency quantized? Do very fine discontinuities exist in a continuous spectrum like the black body spectrum?


We have the following tree. Contact.BOG_Committee__c.BOG_Committee_w_Membership__c   On BOG_Committee_w_Membership__c , I want the contact name.   When I put BOG_Membership__r.Contact__r.Full_Name1__c in my SOQL query which is querying BOG_Committee_w_Membership__c  I get "[object Object]" and not the actual contact name. Why?  FYI, Full_Name1__c is a formula field just concatenating first and last name.


How to draw underline in textblock Windows Phone 8.1 Universal app

Hi i want underling like   how can i add underline like this in Windows Phone 8.1 universal app  I have tried the below solution but seems that it dosent work on wp8.1  <Border BorderBrush="DeepSkyBlue" BorderThickness="0,0,0,1">     <!-- your text --> </Border>


Different behaviour of 'do .. end' and "{..}" block in ruby

Sorry if this question is duplicate. But I can't find the difference in usage. When I run the below codes I am getting different answers. I see from most tutorials that using of "do ... end" is same as "{ ... }" blocks.  include Comparable  a = [1, 4, 2, 3, 5]  p a.sort do |x,y|     y <=> x end   output shows as = [1, 2, 3, 4, 5]  but when I run like this...  include Comparable  a = [1, 4, 2, 3, 5]  p a.sort { |x,y|     y <=> x }   output shows as = [5, 4, 3, 2, 1]  what was wrong here. is there any situations that two syntaxes has any different behaviour?


Proof that in hyperbola sum of squares of a and b is equal to c.

Where c is the focus of the hyperbola.I came across this problem when I was going through the  derivation of equation of hyperbola. A substitution was made there and difference of squares of c and a were replaced by b but no proof of it was given.


On my MacBook Air, I upgraded from Ubuntu 16.04 to Ubuntu 18.04. Everything is fine, but booting with Ubuntu takes approx. 6 minutes!  Running $ systemd-analyze time outputs:  Startup finished in 4.480s (kernel) + 6min 545ms (userspace) = 6min 5.026s graphical.target reached after 6min 535ms in userspace   The final part of $ systemd-analyze time:  ... [    7.005447] Bluetooth: BNEP socket layer initialized [    7.354030] IPv6: ADDRCONF(NETDEV_UP): enx00e04c6800c5: link is not ready [    7.359359] IPv6: ADDRCONF(NETDEV_UP): enx00e04c6800c5: link is not ready [    7.363620] IPv6: ADDRCONF(NETDEV_UP): wlp3s0: link is not ready [    8.977999] r8152 2-1.4:1.0 enx00e04c6800c5: carrier on [    8.978018] IPv6: ADDRCONF(NETDEV_CHANGE): enx00e04c6800c5: link becomes ready [  359.996525] random: crng init done [  693.520385] thunderbolt 0000:07:00.0: resetting error on 0:b. [  693.520465] thunderbolt 0000:07:00.0: 0:b: hotplug: scanning [  693.520471] thunderbolt 0000:07:00.0: 0:b: hotplug: no switch found [  693.820626] thunderbolt 0000:07:00.0: resetting error on 0:b. [  693.820711] thunderbolt 0000:07:00.0: 0:b: got unplug event for disconnected port, ignoring [ 1338.638266] thunderbolt 0000:07:00.0: resetting error on 0:b. [ 1338.638283] thunderbolt 0000:07:00.0: 0:b: hotplug: scanning [ 1338.638288] thunderbolt 0000:07:00.0: 0:b: hotplug: no switch found [ 1338.938543] thunderbolt 0000:07:00.0: resetting error on 0:b. [ 1338.938568] thunderbolt 0000:07:00.0: 0:b: got unplug event for disconnected port, ignoring [ 1357.411889] Bluetooth: RFCOMM TTY layer initialized [ 1357.411894] Bluetooth: RFCOMM socket layer initialized [ 1357.411900] Bluetooth: RFCOMM ver 1.11 [ 1358.945100] rfkill: input handler disabled   The etc/fstab file:  ... # <file system> <mount point>   <type>  <options>       <dump>  <pass> # / was on /dev/sda4 during installation UUID=2ef34bb8-5360-460a-8a8a-646d3a102a3a /               ext4    errors=remount-ro 0       1 # /boot/efi was on /dev/sda1 during installation UUID=67E3-17ED  /boot/efi       vfat    umask=0077      0       1 # swap was on /dev/sda5 during installation UUID=7c820859-65c5-44ac-9704-b3e0bb8c8020 none            swap    sw              0       0   How can I further troubleshoot and possibly solve this problem? Thank you in advance.  Mario


Basically I am trying to implement this solution:  using this MWE:  \documentclass{scrartcl} \usepackage[style=authoryear-ibid,backend=biber,dashed=false]{biblatex} \DeclareLabeldate{\field{date}\field{eventdate} \field{origdate}\literal{nodate}}  \begin{filecontents}{\jobname.bib} @online{Example,   author = {Zuiop, Qwert},   title = {TITLE 1},   urldate = {2014-04-15} } @online{Example2,   author = {Zuiop, Qwert},   title = {TITLE 2},   date={2012},   urldate = {2013-04-15} } @online{Example3,   author = {Zuiop, Qwert},   title = {TITLE 3},   urldate = {2013-04-15} } @online{Example4,   author = {Zuiop, Qwert},   title = {TITLE 4},   date={2012},   urldate = {2013-04-15} } \end{filecontents} \addbibresource{\jobname.bib} \addbibresource{sources.bib}  \begin{document} Test\autocite{Example} Test2\autocite{Example2} Test3\autocite{Example3} Test4\autocite{Example4}  \printbibliography  \end{document}   This results in:    However, the first two entries should contain "(n.d.[a])" / "(n.d.[b])", too:     Zuiop, Qwert (n.d.[a]). TITLE 1. (Visited on 04/15/2014).   Zuiop, Qwert (n.d.[b]). TITLE 3. (Visited on 04/15/2013).   Zuiop, Qwert (2012a). TITLE 2. (Visited on 04/15/2013).   Zuiop, Qwert (2012b). TITLE 4. (Visited on 04/15/2013).     How can I get this to work? I don't see any differences to the linked example which could cause this issue.


Travelling from Berlin to Mumbai to Goa, how long would I need for processing in Mumbai before my flight to Goa?

I am travelling from Berlin to Goa via Mumbai. According to the latest guidelines I need to take a PCR test on arrival and get my receipt before I can take the connecting flight. Can someone who has recently travelled, please shed some light on how long it might take on average to exit the flight, complete immigration, take the test and proceed to the transit gates?


Why is the iterator preincremented when using with map.begin()?

in the example at      // map::begin/end #include <iostream> #include <map>  int main () {   std::map<char,int> mymap;   std::map<char,int>::iterator it;    mymap['b'] = 100;   mymap['a'] = 200;   mymap['c'] = 300;    // show content:   for (std::map<char,int>::iterator it=mymap.begin(); it!=mymap.end(); ++it)     std::cout << it->first << " => " << it->second << '\n';    return 0; }   why is the iterator it preincremented in the for loop?


How is Fermat's least time principle proven?

How is  proven? Or it is what usually is observed and is basis for the theories?


Where did Mark Watney get the escape pod in The Martian?

In the end Mark Watney played by Matt Damon escapes in a space shuttle (don't know what it is called). I have watched the movie only didn't read the book, I have some doubts   From where did the space shuttle appear? Why it has only small energy so that he can't reach the crew?   Any help on these will be appreciated.


The difference of two ways generating a list in Python?

When I do an exercise, I want to generate a m*n list , and all the elements are 0. I find an interesting question:  # first way a = [[0]*n]*m a[0][0]=1 # then I find a[1][0]=1,a[2][0]=1....  # second way b = [[0 for _ in range(n)] for _ in range(m)] b[0][0]=1 # in this way, I get the normal effect   I am confused about the first way, what is the * means for list?


Data set size, how many to have a significant result?

How many records (at least) should I have for my correlation (pearson/canonical) to be significant.


I've spent all day on this and have found no solution; I'm trying to graph a cosine plot (y(x) = 2cos(x/4)) and while I have tried to plot the actual function out on pgfplot, the graph just wouldn't work, with either the negative values going on the positive side, or the curves not showing up at all so I decided to just plot the coordinates instead which has technically almost worked. The problem is that my coordinates are pi values but they don't show up as such in the plot and I've tried xticklabels but that isn't working either. This is my code: \begin{tikzpicture} \begin{axis}    [grid=both, minor tick num=4, grid style={line width=.2pt, draw=black!10}, major grid style={line width=.4pt,draw=black!50}, axis lines=middle, enlargelimits={abs=0.1}, width=12cm, height=9cm ] axis y line=middle, axis x line=middle, \addplot[smooth, blue] coordinates {     (-6*pi,  0)     (-4*pi,  -2)     (-2*pi,  0)     (0, 2)     (2*pi, 0)     (4*pi, -2)     (6*pi, 0) }; \end{axis} \end{tikzpicture}  And this is the picture:  What I'm trying to figure out is how to change the values on the x-axis to pi while keeping those on the y-axis as they are. Thanks!


New Privileges page with facebook kind of logo

Is this by-design or some mistake? I see a Facebook icon on the . It is really not looking great if it is the new design.


Missing favourite star while reading posts

I tried the android app and so far I don't see any bugs etc, maybe one crash but I miss button for saving questions.  If this is multiple "question" I apologize for spamming. Would you please add it? Thank you.


use decimal values as attribute params in c#?

I've been trying to use decimal values as params for a field attribute but I get a compiler error.  I found this blog post  saying it wasn't possible in .NET to use then, does anybody know why they choose this or how can I use decimal params?


May seem like a noob question: really, why can't we divide by 0?

Yes, I know, can't be answered, blah, blah, blah.... but here are a few of my theories. I know, plenty of other questions like this, but before marking this as a duplicate, consider this, my mathematical friends:   We know that $ x/x = 1 $. We also know that $ 0/x = 0 $.   Then, considering these to facts, $$ 0/0 $$ could be    $ 1 $, because $ x/x = 1 $ or $ 0 $, because $ 0/x = 0 $   Then, of course we can consider $ x/0 $, where $ x $ can be any real number. Then $ 0/0 $ can be $ 0 $ or $ 1 $, and then the rest according to theory, is $ \infty $ or $ \text {undefined} $. Then how come we say $ \dfrac {x}{0} = \infty $? Or is this only true being $ x \neq 0 $?  Or is it that just for practical sense, we just say that $ x/0 = \infty $? Is it because it is just because it is not computationally possible? Or is it just because $$ \dfrac {5}{\dfrac {1}{2}} = 5(\dfrac {2}{1}) = 10 $$  and then $$ \dfrac {5}{\dfrac {1}{100}} = 500 $$ and then $$ \dfrac {5}{\dfrac {1}{100000}} = 500000 $$ and so the numbers keep on going to $ \infty $ as we get closer to $ 0 $?   I know there are lots of possible answers but then the theory that $ \dfrac {x}{0} = \infty $ even though $ \dfrac {0}{0} $ could be 1 or 0, that just does not make sense to me. I will appreciate any answers / at lease possible answers, because I understand that this is just a very controversial topic of mathematics.


Show this equality (The factorial as an alternate sum with binomial coefficients).

Why does the following equality hold? $$n!=\sum_{k=1}^n (-1)^{n-k} \binom{n}{k} k^n$$


What is the meaning of biasing in electrical/electronics circuits? What is the need for biasing in BJT/MOSFET? What will happen after biasing when we apply input signal(AC/DC)? Will biasing signal and input signal superimpose?


Have lost all Google information to allow me to sign into my Google accounts

Have been trying to login to my accounts and not able to as I have forgotten all emails, passwords, username and how I sign up as per name.  Have no idea estimated (date) when I signed up but has been years.  No memory of password or hint of one. Thinking of going into Hardware and Features and just deleting Google completely but don't know if that is the correct way and then open another account.


This  explains how energy curves spacetime. But I would like to know why energy curves spacetime, is there something like particle interaction that produce this result?


Fitting lognormal distribution from D10, D50, and D90

I have a statistical sample where D10 = 8 (10% of population under the value 8), D50 = 11 (median), and D90 = 18 (90% of population under the value 18)  Now, I need to find the best fit, in terms of the values $\mu$ and $\sigma^2$ of a lognormal probability distribution, given these D values.   Any help is highly appreciated


How can i verify $(a+b)^\frac{1}{n} \le a^\frac{1}{n} + b^\frac{1}{n}$ for all 'a' and 'b'. are positive real no.

I am trying to solve this problem. But I do not have any perfect proof of that.


Regular expression for US toll free number

What is the regular expression for USA toll free number 1 800 ###-####? How to validate this for phone using c#?


Has anyone ever noticed a meaningful SEO difference, between the use of A 'hierarchical' URL and its shorter variant?

When putting together an ecommerce website structure, one of the ongoing questions I keep asking myself, is:     What would I need to do, in the event of future product expansion.  Ideally, how can I 'future proof' said website.   More specifically, let's say the site has the following Product structure:   Wall Art > Wooden Wall Art > Product Name   This would typically create the following URL structure:  www.example.com/wall-art/wooden-wall-art/product-name/   So far, fairly simple!  Then, 12 months later, the site decides it would like to expand its product offering.  It now wishes to sell Clocks.  As such, it would like to create a 'Wall Decor' Product Category.  As such, the site would have the following Product structures:   Wall Decor > Wall Art > Wooden Wall Art > Product Name Wall Decor > Clocks > Wooden Clocks > Product Name   Referring to the 'Wooden Wall Art' Product structure, we can now see that the URL has changed from ...  www.example.com/wall-art/wooden-wall-art/product-name/   to ...  www.example.com/wall-decor/wall-art/wooden-wall-art/product-name/   Consequently, requiring the implementation of various '301 Redirects'.  It has been said that '301 Redirects' do not affect SEO.  Regardless, I would like to avoid this avenue as I personally as it adds a few extra milliseconds to a site load speed.  Also, I associate redirects with pop up ads etc.  Some people may feel the same and as such, may immediately click off as soon as a page starts to redirect.  As such, I am contemplating the idea of getting rid of a 'hierarchical' URL altogether.  Let's say, someone wishes to visit:   Wall Art > Wooden Wall Art   Instead of the generated URL being ...  www.example.com/wall-art/wooden-wall-art/   ... it would be:  www.example.com/wooden-wall-art/   Say the site should expand to include a 'Wall Decor' Product Category, then the user would still be taken  to ...  www.example.com/wooden-wall-art/   Rather than ...  www.example.com/wall-decor/wall-art/wooden-wall-art/   In order to generate the required internal linking, between Product Categories, all Category Pages would have Breadcrumbs.  It would be through these Breadcrumbs, which would highlight the linking structure.  Prior to adopting this approach, I am wondering if anyone is aware of any potential SEO issues or whether this would cause any other problems; be it SEO or organisational related.  As a side not, I realise that the Product pages themselves would be unaffected.  The reason being that all Product pages would have the following URL structure:  www.example.com/product/product-name/   with all ...  www.example.com/product-category/product-name/   URL variants containing a Canonical link.


It is known that if two matrices $A,B \in M_n(\mathbb{C})$ commute, then $e^A$ and $e^B$ commute. Is the converse true?     If $e^A$ and $e^B$ commute, do $A$ and $B$ commute?   Edit: Addionally, what happens in $M_n(\mathbb{R})$?  Nota Bene: As a corollary of the counterexamples below, we deduce that if $A$ is not diagonal then $e^A$ may be diagonal.


Photons acting as carriers of both attractive and repulsive forces

I understand, in basic terms, how a photon, whilst not being electrically charged itself, is viewed as creating electrical repulsion by means of positive momomentum transfer between two negatively charged electrons.  In most introductory quantum mechanics and basic quantum field theory textbooks this repulsive momementum transfer picture is almost always used as a (in classical terms) billiard ball type illustration for electrical repulsion, the Compton effect and so on.  As a photon is a photon is a photon..... I would like to know how it also has the ability to produce atttraction and how negative momentum transfer (such as that between a positively charged object, say a positron and an electron) is explained in any sort of visualisable picture. I'm guessing this may involve Feymann diagrams and the use of time reversal but I'm on shaky ground from there on.


I have prepared strawberry sauce by cooking strawberry with sugar, squeezing juice of a lime. The mixture was cooked for 10 minutes and mashed. Chia seeds were added in the end and cooled. Strawberry season is ending soon and I would like to make more of this if it can last for few months. Since I have not cooked it long enough to turn into a jam am unsure of its shelf life. How long can I store it in regular refrigerator and how long would I be able to store it in a chest freezer. I plan to deep freeze it in a chest freezer and thaw/reheat it when required.


Can I "tip" someone who left a good comment on my answer?

Sometimes I post a "good" answer to a question, but then it turns out I missed something.  Someone else comes along and points out my error/omission in a comment, and I change my answer.  My answer is now better, freshly active, and I get more upvotes.    However, I kind of feel that I owe that commenter a little bit of the credit (and therefore rep) for having helped support my answer.  I can upvote the comment, but there's no rep gain for that.  Is there any way I can give the commenter a portion of the rep I gain from further upvotes to what is now our answer?  I don't mind some approved existing solution, or some new totally manual solution, but it seems like it could be automated as well.  A similar question was asked in a comment to an answer here:    and one suggestion (which was not popular) was to find some other questions/answers by the helpful commenter and upvote them.  I'm kind of in agreement that each post should gain upvotes of its own accord, and besides, there may not be enough other posts by that user to fully compensate them for their assistance.


How to change the font size of verbatiminput to footnotesize?

I'm using the following code in latex for inserting R output from the package verbatim. First I put the output in a text file then call it from the following code, \verbatiminput{2.txt}  The font size is a bit big. How can I change the font size to footnotesize for all the command \verbatiminput{}?


Noise cancelling speakers to cancel sound in the room

A thought of mine from class, where not everyone is the "silent kid" type. The teacher would very often need to shout to keep the class barely quiet enough for the students who actually are paying attention. This drives me insane, and I often wish there was a way I could silence the entire classroom.  My idea comes from a feature headphones have, noise cancelling. The way I understand it, a microphone takes in the ambient sound and creates a similar sound at a different phase such that the two sound waves cancel each other out inside the listener's ear. My question is: can I route that other wave back out through a speaker such that the entire class can't communicate the "usual" way? An  suggests that such a device would break conservation of energy, but I could be understanding it incorrectly.


How to rename multiple files sequentially from command line?


How to overload and reuse class constructor java

I believe this is a rather easy question to answer, and is probably a repost.  Thing is, I don't exactly know what to search for. I've tried searching for generic terms regarding overloading, but I can only find examples of different ways to use different types or number of arguments.  I think it's easier to understand the problem with an example:  Let's suppose I have an Adder class, which allows me to add two integers, but I want to be able to call it with only one integer, using 1 as the second integer:  public class Adder {     int sum;      public static void main(String[] args) {         Adder myAdder = new Adder(3);         myAdder.printSum();     }     public Adder(int a, int b) {         this.sum = a + b;     }     public Adder(int a) {  // Overloading for default behaviour         return Adder(a, 1);     }     public printSum(){         System.out.println(this.sum);     } }   As you can see, I'm trying to add a new constructor for a single integer, where it just calls Adder(a, 1) instead, but constructors can't return anything, as far as I'm concerned.  What am I missing to do this?


I am trying to model a Lamorghini which has some sharp edges.  The problem is when I create a mesh for the bonnet and use smooth in a left window all hard edges are gone (red in first picture).  I am watching lots of tutorials all over the internet but so far I haven't found the answer for my specific question. When I smooth the bonnet in the left menu (smooth faces) all my hard edges are gone and I have no idea how to bring them back.   Additionally there should be a sharp edge where is the clipping edge with the mirror part of the car (in the middle). There is always some stupid shading on it, I tried to get rid of it by pressing ctrl + m and it worked a bit but I need sharp edge there also. I simply want to model exactly the shape which is in the reference photo of the red lambo. And I want to have it smooth without seeing the faces.  Your kind advice would be really appreciated. (The rendered picture I provided has the lines and smoothness as I want it but the bonnet is created from 3 different parts separately and when i put them together with ctrl + j those nice edges will dissappear again)


What do you call those divisions of a book bigger than a paragraph but smaller than a chapter?

In printed books, or at least in novels, there are often major breaks within a chapter more important than paragraphs.  Often they are separated by a greater amount of whitespace than paragraphs and sometimes this whitespace will contain special symbols such as ⁂ or * * * or even a custom symbol.  So is there a specific term for these, perhaps used by authors or in the publishing industry? Or are the more general terms like section and subchapter the best we have? Some online sources at least seem to say this is used for subdivisions smaller than a subchapter, which doesn't help much.


Do I need a transit visa for Amsterdam for my route - Nairobi to Berlin. I am traveling from Nairobi to Berlin via Amsterdam. My flight is KLM.


I'm making a desktop dictionary which gives meaning with audio pronouncation and also user could record his pronouncation in .wav format..... and the application would tell him how prefect he is in his pronouncation.......! I want to known whether there is way that could help me in comparing the audio file in .wav format....? *Not the size actually but the pronouncation.....* I'm using visual studio 2008


Are the conjugacy classes normal subgroups in $S_n$?

I am working on proving that if $C$ is a conjugacy class in $S_n$ then $C^g =C$ for all $g \in S_n$. I went over similar questions which only prove that a normal subgroup is contained in union of conjugacy classes, but not claiming a conjugacy class is normal subgroup.


In the following scenario, does a double word premium apply to both words made on the same turn? Player 1 plays the word "book". Player 2 plays the word "shot", placing the "s" on a double word score space, and also forming the word "books".


Find all the places where a block type is used

I have a plugin installed that adds additional custom block types that can be used in the Gutenberg editor (the plugin is called Block Lab). Now I want to remove that plugin. For that, I have to remove all the used instances of those blocks. Is there a way to find all the occurrences of a used block type?


Unit testing with SOAP and REST callouts

My project assumes quite big integration with external webservices. Unfortunately first major service is SOAP and second is REST.  Problem is that there are getting more and more places in the code where for example SOAP callout needs some value from different REST callout. Putting this methods inside one wrapper is impossible for me to test since Apex is allowing only to mock one type of callout at the time (either REST or SOAP).  Question: How to create unit test with mocks for both callouts to achieve 100% code coverage of the wrapper method?


I am creating a 2D platform game in a wpf application... and I tried to make my character walk with a gif animation.  Here's my C# code:  private void imgMega_OnKeyDown(object sender, KeyEventArgs e)         {             if (e.Key == Key.Right)             {                 if (Grid.GetColumn(imgMega) <= Grid.ColumnDefinitions.Count - 1)                     Grid.SetColumn(imgMega, Grid.GetColumn(imgMega) + 1);                 BitmapImage bmi = new BitmapImage(new Uri("megaman.gif", UriKind.Relative));                 imgMega.Source = bmi;              }         } /*---- When my character walk ----*/          private void imgMega_OnKeyUp(object sender, KeyEventArgs e)         {             BitmapImage bmi = new BitmapImage(new Uri("Megaman8bit.jpg", UriKind.Relative));             imgMega.Source = bmi;         } /*---- When my character stop walking ----*/   And my XAML code:  <Image Name="imgMega" Width="60" Grid.ColumnSpan="4" FocusVisualStyle="{x:Null}" Source="Megaman8bit.jpg" Focusable="True" KeyDown="imgMega_OnKeyDown" KeyUp="imgMega_OnKeyUp"/>   * My "megaman.gif" image is my walking character and my "Megaman8bit.jpg" image is my immobile character. *  With this code, the character changes his position but the gif animation doesn't work... Somebody can help me to find what's wrong ?


What are the limitations on the "Dueling" fighting style for Fighters?

So I was looking over the wording for the fighting styles for Fighters, and I notices the wording for the Dueling Fighting Style (p. 72 PHB) seemed to allow for more options than you would automatically assume.     Dueling: When you are wielding a melee weapon in one hand and no other weapons, you gain a +2 bonus to damage rolls with that weapon.   So if I am reading this correctly... and I'd like to think I am, I could take this as a fighting style, and still use a shield in my other hand, since, as it was worded, it's not a weapon.  Now of course this whether you could do this or not, at the end of the day is at your GM's discretion, but as far as the rules go as stated in PHB it is a viable course of action, yes?


I'm trying to order by WeekId, then Order in my SQL table (end result should have workouts together by id, then ordered by the order specified), yet it is giving the wrong order. Is there something wrong with my LINQ statement?  private List<Workout> GetWorkouts(int id) {     return new OPPDBContext().Workouts         .Where(p=>p.ClientId == id).OrderBy(p => p.Order).OrderBy(p => p.WeekId).ToList(); }   The table:    The results:    Expected results:   Lat Pulldowns  Squats  Lat Pulldowns  Squats  Reverse Lunges


I am trying to install sshd on my Ubuntu system but I am unable to do so. I tried below things.  sudo apt-get install openssh but I received below error.   When I am checking with which command for ssh, I am getting result for ssh but not for sshd.  While checking for status of ssh, I am getting an error of unrecognized service.   Please help me to overcome this as I am new to Ubuntu and I need both ssh and sshd to be available in my system.


This is how I started toggling classes:  $(document).ready(function() {     window.setInterval(function() {         $('.blinkClass').toggleClass('blink');     }, 500);   });   How can I stop toggling these classes?


Regular expression diffrence between [waz{2,3}up] and waz{2,3}up

Exercise 6: Matching Repeated Characters Task    Text      Match   wazzzzup    Success Match   wazzzup Success Skip    wazup   I came up with [waz{2,3}up].  What I meant was matching character w, a and z, with z in repetition 2-3 times, followed by u and p. But without [] was the answer


Why didn't Severus Snape from Harry Potter kill Nagini?

It's stupid how Snape didn't resist Nagini when Voldemort ordered Snape's death.


How to customize 19.10 Desktop Icon Font Size

I'm searching how to customize the desktop icons font size on Ubuntu 19.10 GNOME (standard) edition. For example, i Want 8px.  With 18.04, it was as simple as   gsettings set org.gnome.nautilus.desktop font 'Ubuntu 8'   On 19.10, there is no org.gnome.nautilus.desktop schemadir. I searched inside all  parameters gsettings list-recursively and dconf dump /, cannot find any related to desktop icons font.


I know there is a question  but I checked its answers and it didn't help. I'm just learning developing modules for Drupal so maybe it's something really stupid but I have no idea...  My hook (in testModule4.install):  function testModule4_update_7001() {  $schema['testModule4_table'] = array(     'description' => 'TODO: Description',     'fields' => array(         'main_id' => array(             'description' => 'TODO: Description.',             'type' => 'serial',             'not null' => TRUE,         ),         'settings' => array(             'description' => 'TODO: Description',             'type' => 'text',             'not null' => FALSE,         ),         'uid' => array(             'description' => 'TODO: Description',             'type' => 'int',             'not null' => FALSE,         ),         'created' => array(             'description' => 'TODO: Description',             'type' => 'int',             'not null' => FALSE,         ),         'changed' => array(             'description' => 'TODO: Description',             'type' => 'int',             'not null' => FALSE,         ),     ),     'primary key' => array('main_id'), );  db_create_table('testModule4_table', $schema['testModule4_table']);  }   My module is working just fine. The schema_version of module in database is 0 but update.php just cannot see it. What can be the cause of that? :/ I was trying clearing cache and reenabling a module but without success. I just don't know where to search for source of the problem. If you need more data, just comment :/ .  Edit:  I created simple module:  testModule.module:  <?php   function testModule_myform($delta = "") {      $form['something'] = array(         '#type' => 'markup',         '#markup' => 'Something',     );     return $form; }    /**  * Implements hook_menu();  */  function testModule_menu() {     $items["test/test"] = array(         'title' => 'testModule',         'description' => 'TODO: Description',         'page callback' => 'drupal_get_form',         'page arguments' => array('testModule_myform'),         'access callback' => TRUE,      );     return $items; }   testModule.info:  name = testModule description = Test module for Drupal experiments. package = CustomTest core = 7.x   testModule.install:  function testModule_update_7001() {     drupal_set_message('It works!');     print 'Show something!'; }   And it still ignores this hook... Is it officially a Drupal bug and I need to reinstall the whole Drupal? >_<


jQuery mouseenter does not want to trigger

I just don't know how to make mouseenter event on trigger on certain element and to perform an action on the other. Here is the thing, i'm trying to make an dropdown menu but not in an ordinary way (submenu nested in an li of the main menu) but to make submenu appears bellow main menu when mouse enters zone of a certain element and submenu should hide when mouse leaves area of submenu. Mouseenter just does not trigger when mouse enters zone of desired element of the main menu. (I tried with console.log but the event just isn't triggering) It's really annoying because mouseleave normally triggers when I deleted initial property display: none, to display submenu initially and when I left area of submenu event worked properly and submenu hid. Does anybody know what the solution is? Function that generates code, annoying events and HTML:     function showMenu(menuJsonData){     var writingMenu = "";     var writingSubmenu = "";     for (partOfMenu in menuJsonData){         if(menuJsonData[partOfMenu].primaryHref!="#"){             writingMenu+=`<li>                             <a href="${menuJsonData[partOfMenu].primaryHref}" class="whiteColor linkMarginLeftRight">${menuJsonData[partOfMenu].primaryLabel}</a>                         </li>`;         }         else {             writingMenu+=`
                             ${menuJsonData[partOfMenu].primaryLabel}
`;             for (partOfSubmenu in menuJsonData[partOfMenu].secondaryHrefs){                                     writingSubmenu+=`
                                                      ${menuJsonData[partOfMenu].secondaryLabels[partOfSubmenu]}
`;             }             document.querySelector("#submenu").innerHTML=writingSubmenu;         }     }     document.querySelector("#menu").innerHTML=writingMenu; }  $("#includesSubmenu a").mouseenter(function(){     console.log('Clint Eastwood');//event doesn't trigger    $("#submenu").parent().parent().removeClass("displayNone");  });  $("#submenu").mouseleave(function(){ console.log('Al Pacino');// event does trigger      $("#submenu").parent().parent().addClass("displayNone"); });


Can "zero hours contracts" be considered as not grammatical?

Zero hour contract (or zero-hour contract) can be found :                    But more frequent with an s:              or hyphenated:        (to note that this Independent article mixes hyphenated and non hyphenated forms in the same article)  My question is not about zero+plural noun, I am aware of ,  but on the "s" being left when "zero-hour" is used in front of a noun, i.e. as an adjective.   I've noticed that "hours" is sometimes (but rarely though) used, in for instance, "" or "" but "eight-hour day" and "eight-hour shift" seem to be more frequent.   The only explanation I can think of is that an apostrophe ('s) has been lost somewhere in the process and thus should not correct spelling have been either zero-hours' contract or zero-hour contract?  If not why are the usual forms "eight-hour day" (no s) and "zero-hours contract"?


Prove that for all $n\geqslant 1$ we have $F_n<{\left(\frac 74\right)}^n$.

Recall that the Fibonacci sequence is defined by $F_0=0, F_1=1$ and $F_n =F_n−1 +Fn−2$, for $n\geq 2$.  Prove that for all $n\geq 1$ we have $F_n<{\left(\frac 74\right)}^n$.


Show that $(\mathbb{Z}/n)^\times$ cannot be cyclic unless $n$ is either a prime power or twice a prime power.

Q: Show that $(\mathbb{Z}/n)^\times$ cannot be cyclic (i.e., there is no   primitive root modulo $n$) unless $n$ is either a prime power or   twice a prime power.  I'm reading a solution. The first step is that for any $n$ it can be factorized into three relatively prime terms: $n = 2^r \cdot p^s \cdot m$ where $p$ is prime.  Since these terms are relatively prime, we can say that:  $(\mathbb{Z}/n)^\times \cong   (\mathbb{Z}/2^r)^\times \times (\mathbb{Z}/p^s)^\times \times (\mathbb{Z}/m)^\times$  The next step claims that for $(\mathbb{Z}/n)^\times$ to be cyclic, at most one of the three factored groups can be an even cyclic group. Why is this statement true? I know what cyclic groups are, does "even cyclic" just mean a cyclic group of even order?


I'd like to know whether "was" or "were" should be used in the main clause of the following:     If there were a 200-story office building without an elevator, those whose office was / were on the 180th floor would climb many steps each day.   I'd appreciate your help.


How can I download music from YouTube and not the video film?

I want to know if is there any programme to download music from YouTube, not video, just audio, like DVDvideosoft in Windows.


Check file extension in upload form in PHP

I check the file extension for upload or not uploaded. My example methods worked, but now I need to understand if my methods (using pathinfo) is true. Is there another better and faster way?  $filename = $_FILES['video_file']['name']; $ext = pathinfo($filename, PATHINFO_EXTENSION); if ($ext !== 'gif' || $ext !== 'png' || $ext !== 'jpg') {     echo 'error'; }


Brief outage where all questions were gone

Just now, none of the sites I visited had any questions:        I don't belong to Politics, but in addition to this I was getting a 404 by going to this .  For sites that I belonged to, I was getting the error "it was not possible to perform this tag search at this time due to an unexpected error.":      (Both of the above are pictures from the home page.)


Search Gmail for e-mails with no tags (labels) (or just the `Inbox` tag)?

I try to put at least one tag on each e-mail that comes in, but sometimes I miss some.  Is there any way to search for all untagged e-mails in Gmail (or all e-mails with just the Inbox tag)?  Right now the only way to find Gmail e-mails with no tags (or with only the Inbox tag) is to scroll through my list of all e-mail and look for myself...terrible.  I would like a way to get a list of all e-mails with no tags (or with only the Inbox tag).  I have tried a search term with "-[Tag1] -[Tag2] -[Tag3] [...]" with "-" in front of all of the tags I use, but that does not work.  If it or something like it did work, even being while long and awkward, I would still use it since it would be better than what I currently have to do!    Edit:  I originally typed this out referring to "tags", the non-Gmail-centric word for "labels".  Right before submitting I remembered the Gmail-centric term and changed those words to "labels" before submitting the question.  I have now put the question back to the original way I wrote it so that people searching using search term "tags" (like I did, which is why I did not find ) will find an answer.


Theresa May to press Trump at G7 to reverse metal tariffs .   Link to this news was   The first "to" is vague for me but second "to" would mean "in the means of". So, I would be glad for some help !


Proof explanation: Hahn-Banach Theorem in Stein's functional analysis

Theorem: Let $V$ be a linear space and $V_{0}$ is its subspace. Also let $p$ be a finite convex functional in $V$ and $l_{0}$ is linear functional in $V_{0}$.   While $l_{0}(v)\le p(v),v\in V_{0}$   Then exists linear functional $l$ defined in $V$, which is extension of functional $l_{0}$ and   $l(v)\le p(v),v\in V$      Stein's proof in functional analysis page$_{21}$ :     ......   Well-order all vectors in $V$ that do not belongs to $V_0$ , and denote this ordering by $\lt$ . Among these vectors we call a vector $v$ "extendable"if the linear functional $l_0$ has an extension of the kind desired to the subspace spanned by $V_0 , v$ and all vectors $\lt v$ . What we want to prove is in effect that all vectors not in $V_0$ are extendable .   ......     Since we can not apply well-ordering principle to find the largest element in $V$ . If we have proved all vectors not in $V_0$ is extendable , then how to show $V$ is extendable ?


modprobe: FATAL: Module rtl8723de not found. Ubuntu 18.04 on HP Pavilion

I am facing the common problem of adapter not found on Ubuntu 18 while trying to connect wifi. I followed this  These steps: sudo modprobe -r rtl8723de sudo modprobe rtl8723de  give me "module not found error". So, I ran: lspci -nn and got 00:00.0 Host bridge [0600]: Intel Corporation Mobile PM965/GM965/GL960 Memory Controller Hub [8086:2a00] (rev 0c) 00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) [8086:2a02] (rev 0c) 00:02.1 Display controller [0380]: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (secondary) [8086:2a03] (rev 0c) 00:1a.0 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #4 [8086:2834] (rev 03) 00:1a.1 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #5 [8086:2835] (rev 03) 00:1a.7 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #2 [8086:283a] (rev 03) 00:1b.0 Audio device [0403]: Intel Corporation 82801H (ICH8 Family) HD Audio Controller [8086:284b] (rev 03) 00:1c.0 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 1 [8086:283f] (rev 03) 00:1c.1 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 2 [8086:2841] (rev 03) 00:1c.2 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 3 [8086:2843] (rev 03) 00:1c.3 PCI bridge [0604]: Intel Corporation 82801H (ICH8 Family) PCI Express Port 4 [8086:2845] (rev 03) 00:1d.0 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #1 [8086:2830] (rev 03) 00:1d.1 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #2 [8086:2831] (rev 03) 00:1d.2 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #3 [8086:2832] (rev 03) 00:1d.7 USB controller [0c03]: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 [8086:2836] (rev 03) 00:1e.0 PCI bridge [0604]: Intel Corporation 82801 Mobile PCI Bridge [8086:2448] (rev f3) 00:1f.0 ISA bridge [0601]: Intel Corporation 82801HM (ICH8M) LPC Interface Controller [8086:2815] (rev 03) 00:1f.1 IDE interface [0101]: Intel Corporation 82801HM/HEM (ICH8M/ICH8M-E) IDE Controller [8086:2850] (rev 03) 00:1f.2 SATA controller [0106]: Intel Corporation 82801HM/HEM (ICH8M/ICH8M-E) SATA Controller [AHCI mode] [8086:2829] (rev 03) 00:1f.3 SMBus [0c05]: Intel Corporation 82801H (ICH8 Family) SMBus Controller [8086:283e] (rev 03) 05:00.0 Ethernet controller [0200]: Marvell Technology Group Ltd. 88E8039 PCI-E Fast Ethernet Controller [11ab:4353] (rev 14) 07:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4312 802.11b/g LP-PHY [14e4:4315] (rev 01) 08:09.0 FireWire (IEEE 1394) [0c00]: Ricoh Co Ltd R5C832 IEEE 1394 Controller [1180:0832] (rev 05) 08:09.1 SD Host controller [0805]: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter [1180:0822] (rev 22) 08:09.2 System peripheral [0880]: Ricoh Co Ltd R5C592 Memory Stick Bus Host Adapter [1180:0592] (rev 12) 08:09.3 System peripheral [0880]: Ricoh Co Ltd xD-Picture Card Controller [1180:0852] (rev 12)  Now which driver do I require? What steps do I have to follow?


i have 24gb RAM and 4 core LEMP server for run one application with Websocket PHP/Mysql but the problem is cpu going over 10-18% for just one user  I dont know if server can crash with many users (over 100 in the same time) ?  Im on Debian 7  My config (i add random number)  key_buffer              = 800M max_allowed_packet      = 16M thread_stack            = 192K thread_cache_size       = 8 myisam-recover         = BACKUP max_connections        = 1000 query_cache_limit       = 10M query_cache_size        = 124M log_slow_queries        = /var/log/mysql/mysql-slow.log long_query_time = 1 #log-queries-not-using-indexes   #innodb_read_io_threads=4 #innodb_write_io_threads=8  #To stress the double write buffer #innodb_buffer_pool_load_at_startup=ON #innodb_log_file_size = 32M #Small log files, more page flush #innodb_log_files_in_group=2 #innodb_file_per_table=1 #innodb_log_buffer_size=8M #innodb_flush_method=O_DIRECT #innodb_flush_log_at_trx_commit=0  skip-name-resolve innodb_buffer_pool_size=1G innodb_buffer_pool_size = 3G innodb_thread_concurrency = 12  [mysql] #no-auto-rehash # faster start of mysql but no tab completition   fpm/php.ini  memory_limit = 1024M   memcached.conf  -m 1024   Nginx  worker_processes  3;   This configuration is good or i need to decrease ? Thanks you


representing f as a sum of symmetrical and antisymmetrical bilinear forms

i've tried to solve this following question without any success. can you help me with it please?  let $V=M_{2 \times 2}^\mathbb{R}$ and $f: V \times V \to \mathbb{R}$ so that $f(A,B)=tr(A^tMB)$ for every $A,B \in V$. when n=2, $V=M_{2 \times 2}^{\mathbb{R}}$ and $M=\begin{pmatrix}1&2\\ 3&5\end{pmatrix}$  find a representation of f as a sum of a symmetrical bilinear form and an anti-symmetrical bilinear form.  what i tried:  since from the details we can infer that in order for f to be symmetric, M must be equal to $M^t$ ($M=M^t$). now for a bilinear form to be symmetrical we need that $B(u,v)=B(v,u)$ for every $u,v \in V$, and for a bilinear form to be anti symmetrical it must follow $B(u,v)=-B(v,u)$. but i don't get to finding a representation of f as a sum of a symmetrical and anti symmetrical bilinear forms using the given values.  please help me if you can.   thank you very much.  (edit: this is not a theoritical question about proving that every biliear map can be written as a sum of biliner symmetric map and a bilinear anti-symmetric map. This question is about implementing the theory using the given details in order to obtain the needed representation. additionally, on that thread the answer is incomplete and not enough for me in order to solve this question. thank you very much).


Logo formats for a web site and digital photographs and using for print

Someone is designing a logo for me. I need to use it for a web site, as a watermark on digital photograph as well for printing on photos, business cards, etc. What formats should I confirm for all purpose? Should it be easy for them to provide all formats requested.


Can the Telekinesis spell be used to manipulate liquids?

The description of the  spell in the PHB states, under the "Object" section of the spell:  You can try to move an object that weighs up to 1,000 pounds. [...] You can exert fine control on objects with your telekinetic grip, such as manipulating a simple tool, opening a door or a container, stowing or retrieving an item from an open container, or pouring the contents from a vial.  For reference, the definition of  is:   a material thing that can be seen and touched.   The answers to the question  seem to imply that any material that is inanimate is an object. However, the use of 'object' does not jibe well with what I typically consider to be an object, as I would say that an object needs to be discernible from its surroundings, something you can pick up and manipulate. Is uncontained liquid (like a puddle of water) considered an object? Can it be controlled with telekinesis?


ffmpeg: extremely precise extraction of video segments

I want to extract segments of video with extremely precise start and end points. Unfortunately I'm only seeing accuracy to a hundredth of a second.  ffmpeg -i kayak.mp4 -ss 00:00:00 -t 2.86953 kayak_segment.mp4   Though I expect this segment to have a duration of 2.86953, analysis on the outputted segment shows 2.891.  ffprobe -i kayak_segment.mp4 -show_format -v quiet | sed -n 's/duration=//p'   (returns 2.891000)  How do I best ensure that the durations of extracted video segments are as close to what is specified as possible? I'm not concerned about audio.  Thanks!


Simple proof that equilateral triangles have maximum area

Using Lagrange multipliers, it can be shown that a triangle with given perimeter has the maximum possible area, if it is equilateral. Is there a simple geometric proof of that fact ?


why is there only a referenced before assignment error for int values but not lists inside a nested function?

I'm doing a leetcode problem - rightSideView. When I create an inner helper function, I thought I'd have access to the outer function variables. However, that only holds true for result (a list) but not maxHeight (an int). Code referenced below: class Solution(object):     def rightSideView(self, root):        result = []        maxHeight = 0        def dfs(node, height):            if node is not None:                height += 1                if height > maxHeight:                    maxHeight = height                    result.append(node.val)                dfs(node.right, height)                dfs(node.left, height)        dfs(root, 0)        return result  This can be fixed if I reference self.maxHeight; however I don't have to do the same for result. Why is this? Could it be that lists are created as global variables inside classes in python? Not sure how else to explain this. The following code works without errors: class Solution(object):     def rightSideView(self, root):        result = []        self.maxHeight = 0        def dfs(node, height):            if node is not None:                height += 1                if height > self.maxHeight:                    self.maxHeight = height                    result.append(node.val)                dfs(node.right, height)                dfs(node.left, height)        dfs(root, 0)        return result


How common is it to have multiple muggle-borns in a single family?

covers individual Muggle-Born, but this is about multiple in the same family. For instance, Collin Creevey introduces himself to Harry as a Muggle-Born in Chamber of Secrets, saying  "I'm muggle-born, you see. My dad is a milkman. I would love to send a picture of us home to them to prove I've met you."  Though I cannot recall the source, I have read that two muggle-borns in the same family are so rare that it is nearly impossible. Dennis and Collin Creevey, being brothers, are both muggle-born from the same family. Are they just a rare case or is there something else I am missing?


Nullable: and overloaded operators, bool? & bool

Why is operator '&' defined for bool?, and operator '&&' is not?  How exactly does this 1) bool? & bool? and 2) bool? and bool work?   Any other "interesting" operator semantics on Nullable? Any overloaded operators for generic T?


Polymorph Question :: Excess Damage (And resistances)

Ok so if I polymorph a Fire Giant into a Baby Chicken and drop it into Lava the Baby Chicken will take 10d10 or 18d10 if I dunk it.  When it hits 0 it reverts back to its previous form and takes the excess damage, but what if the creature was immune.. like a fire giant? Does it assume to take all that damage because it was a Baby Chicken? Basically Im tryin to turn a giant into a nugget.


Why does blender cover the whole cube and not selected areas with materials?

I have tried a lot of different ways to cover the Roof of my cube with a material, but every time I tried, blender covers the whole cube with the painting color. How can I simply coloring just parts of a cube?


how to add parameter to bash alias without space in between?

We can do with ease:  myalias='command param1 param2'   then myalias param3 runs   command param1 param2 param3   I need an alias which will run the same, but without the last 'space':  command param1 param2param3   For example I have many servers in /24 subnet and need to run the same command using the ip. So I want alias like command param1 192.168.0. then just run myalias 103 and the command will be applied to 192.168.0.103.  I tried to add $1 at the end of the alias but no luck.


The nth prime gap is defined as $p_{n+1} - p_n $, [sequence A001223 in OEIX] (). What values can occur as a prime gap?  Clearly with the exception of $1 = 3 - 2$, all the prime gaps must be even. We also know that this sequence must contain infinitely large numbers, since there are no primes between $n!+2$ and $n! + n$.   Is it true that every even number occurs as a prime gap?


Is there any initiative to start a community about sports?

I was wondering if a community for people who play any sport will be worth. Is there any initiative?


Showing all pages at once with man command

Say if I run the command man who, I have to keep pressing space or enter to show all content. Is there a way to show all of the content at once?


Surjective function: $x^2- \lfloor x \rfloor^2$?

I understand that a function $f$ from a set $X$ to a set $Y$ is surjective, if, for every element $y$ in the codomain $Y$ of $f$, there is at least one element $x$ in the domain $X$ of $f$ such that $f(x) = y$.   Is $x^2- \lfloor x \rfloor^2$ surjective for all real numbers greater than or equal to $0$? I know that it is from graphing it, however, I'm not sure how to formally prove it.


Activating Field of Ruin's ability without a target

The activated ability of  states:     Destroy target nonbasic land an opponent controls. Each player searches his or her library for a basic land card, puts it onto the battlefield, then shuffles his or her library.   Can I use this ability to make all players search out a basic land card even if the first part has no valid target, for example because there is no nonbasic land to destroy?  I am assuming the period matters, and the next section is a different effect that is not contigent upon the first resolving.


What's up with the visited "Hot Network Questions" links?

On some sites (like User Experience), under the "Hot Network Questions" on the side, the links you have clicked on previously are darker than ones you haven't visited (I think this is the way it should be...).  However, on some sites (like Music: Practice and Theory) it is REVERSED! (Links you haven't visited are darker than links you have visited).  This drives me nuts, I always get confused. Is there any reasoning behind this?


HDMI to active dual link DVI (2560x1600px)

Is it possible to go from HDMI to active dual link DVI with a resolution of 2560 x 1600px ? I have a Lenovo E540 laptop, and it only got a HDMI and a VGA out, but I have a 30" Mac Cinema HD screen, which only has a DVI connector.  From several searches I can see that there are plenty of Displayport to active DVI converters, but none from HDMI to active DVI. Now is my question if it's possible to convert HDMI to displayport and go from there with a displayport to active DVI converter. Or is this not possible? If not, are there other possibilities?


Prove using mathematical induction that for all $n! \ge 2^{n-1}$  Base case, p(1), 1! >= 1  $p(n+1), n!(n+1) \ge 2^{n-1}(n+1) $


The set of functions $P$ for which $P(x)^2=P(x^2)$ for all $x\in \mathbb{R}$

We showed that all of polynomials satisfy the equation $$P(x)^2 = P(x^2)$$ are $P(x) = x^n, n \in \mathbb{N}$.   If $P(x)$ is only a continuous function, can we describe the set of solutions of the above equation, i.e., $P(x)^2 =P(x^2)$?


Let $f(z) = z + g(z)$ where $g$ is holomorphic. Suppose that $|Img(z)| < 1$ for $z \in [−1−i,1−i]\cup[−1+i,1+i]$ and $|Reg(z)| < 1$ for $z \in [−1−i,−1 + i]\cup[1−i,1 + i]$. Show that $f$ has exactly one zero on the square $Q = \{x + iy \in \mathbb C : |x| < 1,|y| < 1\}$.  I have been trying to find the appropriate function to compare to $g(x)$ in order to apply the theorem, the most obvious candidate would be the function $h(z) = z$. I can show that this function is greater than $g(z)$ on the corners of the square but not anywhere else.  Any tips? Thanks!


Trying to find the name of a SF short story about earth violent race

Several years ago I Had a book of sci fi short stories and one of the stories in it was amazing. Hopefully someone can tell me the name of the story or the book it was in --  In the short story, some human astronauts in space encounter some aliens. The aliens ask them where they're from, and the astronauts happily tell them from Earth, and then where Earth is located, in the Milky Way Galaxy. The aliens then tell them a story, about how long ago there was a huge intergalactic war, where all races had to come together to defeat one race that was incredibly brilliant but also bloodthirsty and vicious. The bloodthirsty race was ultimately defeated but one of their ships got away and the aliens have been hunting the universe for their descendants for thousands of years. And those descendants are us, humans. The aliens tell the astronauts they're sorry but they have to kill them, and then they're heading to earth to finish us off.   It was an amazing story and chilling. Any one recognize it please??


\documentclass{article}  \usepackage[utf8]{inputenc}  \begin{document}  \maketitle  \text{I can't use the #-symbol}  \end{document}


Is there a way to make Android think it has a different screen size and dpi than what was programmed in its factory settings?  I'm asking because we bought a 7-inch tablet recently, and its interface is too large for a 7-inch tablet. I installed  and it confirmed what I suspected: The tablet thinks its screen is 4.86 inches with 192dpi.  Is there a way to fix this and tell it its screen is 7 inches and 133dpi?  The tablet is Genx GX7-3GS running Android 4.2.2.


is_active_sidebar() Always Returns False

I've never gotten is_active_sidebar() to work, no matter if there's widgets in the sidebar or not I always get false returned. Currently I'm creating a sidebar for each top level page:    I create my own widget(s):    And I'm testing whether the sidebar is active like so:  if(is_active_sidebar(get_the_title()))     echo 'active'; else     echo 'not active';   Even when I manually put the title in: is_active_sidebar('Test'); it always returns false. Am I using the conditional wrong? Do I need to add some sort of setting? Why would is_active_sidebar() fail?


In a ring with identity, prove that (−1) · (−1)= 1.

I'm not sure how to start this problem with Rings, could someone perhaps lead me in the right direction?


I'm currently taking an introductory C++ class and the professor gave us the following example:  unsigned int TEST = -1; cout << TEST;   Now, on his machine, TEST is returned as the maximum value for an integer, because he forced underflow. But on my machine, it is returned as 0.  Is this behavior compiler dependent or anything? In other words, why did my machine return 0 but his machine return the maximum?


This is a question about the classical two envelopes paradox problem. The solution posted in  seems to be uniform across all the sources I've seen. The question is:  Suppose that there are two envelopes. One containing $\$m$ and the other containing $\$2m$. You don't know which envelope contains which. You pick one at random. You want to decide if you should switch to the other envelope under the following conditions (1) You are NOT allowed to open your envelope and see how much is inside. (2) You are allowed to open your envelope and see how much is inside.  The mathematical approach shows that for (1), you don't gain anything from switching because each envelope has an expected value of $\$1.5$. The mathematical approach shows that for (2), you gain  $\$0.25$ from switching to the other envelope. I don't understand the solution for (2). The logic is that when you peek into your envelope and you observe $\$x$, this means that the other envelope has $\$x / 2$ or $\$2x$ with equal probability. I'm not sure if I agree with this, as I think the solution for (2) should be the same as (1). I don't think you can say that the other envelope contains $\$x / 2$ or $\$2x$. Suppose that $x = \$m$. This would mean that if you claim the other envelope contains either $\$x / 2$ or $\$2x$, then that would mean the other envelope contains $\$m/2$ or $\$2m$, but we know that the other envelope contains only $\$m$ or $\$2m$ and there's no envelope with $\$m/2$. The analogous issue occurs if $x = \$2m$. Ultimately, I'm just not seeing how observing how much you have changes anything. Like if I were to simulate this with monte carlo or to do this in real life with two envelopes, I don't see how I'm going to, gain, on average by choosing the other envelope after I open my envelope and see what's inside, so that brings me back to the same situation as not observing what's inside my envelope in the first place. Could someone explain? What if we applied this same logic to a True/False test? Say there are 100 questions, and you know there are 50 false and 50 true answers. Say I initially picked True for all the answers. According to the above logic, I should switch all my answers to False? If that's the case, then I clearly don't gain anything from switching.


Gnome - Cannot click between windows or click on UI elements with Mad Catz R.A.T. 3 mouse

I recently switched to Linux. Everything went fine, but when I installed the gnome-shell, it started to ignore clicks outside the focused window. I cannot click on another window to focus it or click on any gnome UI elements. The super key also does nothing. I installed gnome-tweaks and I use a user theme, but that shouldn't be the problem because the problem remained even when I had a fresh install. Also, sometimes when I reboot it works normally. But after another reboot, it comes back.   PS- I found a very temporary fix: If I move the focused (or sometimes other windows) it will start recognizing my keystrokes. On Firefox I need to move the window by the bar with open tabs, as I cannot move it with the title bar.  I read  by someone who had a very similar issue, but the solution did not work for me. I think it has to do something with NVidia drivers, because if I change them then the frequency of this happening changes.  Sorry if something is weirdly written. English is not my native language.


Why the following expression is evaluated to true?

I want to know why the following expression is evaluated to true.  var_dump(('a' == 0)); //bool(true)


What do you call a mother whose children have died?

For instance, a child whose parents have died is an orphan; while a woman whose husband has died is a widow...


I tried to fix the    :count($analyzed_sql_results['select_expr']   error in  :usr/share/phpmyadmin/libraries/sql.lib.php      but I cannot write to it. Error :      Error writing /usr/share/phpmyadmin/libraries/sql.lib.php: Permission denied


The "of" in company names—avoid or embrace?

Are you aware of any rules, statistics, or guidelines that address the "of" in company names?  For instance, which is more accepted: Institute of Research or Research Institute? Canada Bank or Bank of Canada? What guides the choice?  Thank you in advance.  Justin


Assume $F$ is a field of zero characteristic. Denote the elementary symmetric polynomials of $n$ variables by $e_k$, $\quad k=\overline{1,n}$. Let the symbol $\sum ax_1^{i_1}\dots x_n^{i_n}$ denote the sum of all different monomials which can be obtained from $ax_1^{i_1}\dots x_n^{i_n}$ by permuting its variables. For instance, if $n=3$,  $$\sum x_1^2x_2=x_1^2x_2+x_1^2x_3+x_2^2x_1+x_2^2x_3+x_3^2x_1+x_3^2x_2$$  The polynomials $S_k=\sum_{i=1}^n x_i^k$ are called power sum symmetric polynomials. Obviously $S_1=e_1$ and $S_2=e_1^2-2e_2$. In order to prove Newton's identities one can see that for $2<k<n+1$  $$e_iS_{k-i}=\sum x_1^{k-i+1}x_2\dots x_i+\sum x_1^{k-i}x_2\dots x_ix_{i+1}$$  How can we see the above identity?


I have 397 shapefiles that I need to merge into one shapefile, and I need to add an attribute for the name of each of the shapefiles. I have no experience in coding/ Python.   Is this possible to do without any coding in ArcMap 10.3?


Variable may not have been initialized (a)

import java.util.*; public class lab3 {     public static void main(String args[])     {          Scanner input= new Scanner (System.in);          System.out.println("Enter the height (feet;");          double height;          height= input.nextDouble();          double width;          width= input.nextDouble();          double area;          final double GALLONS_PER_SQUARE_FEET=150.0;          double gallons;          gallons = area/GALLONS_PER_SQUARE_FEET;          System.out.println("The amount of paint is " + gallons + " gallons.");      }//end main }//end class      lab3.java:19: error: variable area might not have been initialized   gallons = area /GALLONS_PER_SQUARE_FEET;


Proof of Euclid's lemma using fundamental theorem of arithmetic

I want a proof of Euclid's theorem (if p is prime and p|(a.b) where a and b are integers, then either p|a or p|b) using the fundamental theorem of arithmetic.  I already understand the proof assuming p is not |a and using gcd(p,a). I want a proof that rely's on FTofA.  Searching on line I can find examples of using Euclid's lemma to prove Fundamental Theorem of Arithmetic but I want to go the other direction, and assuming Fundamental Theorem of Arithmetic, prove Euclid's lemma.


If $n$ and $p$ are coprime how it will be true for some $x$ and $y$. $Nx+ py = 1$


Get last full backup and transaction log backup for each database

How to write script or a query that will display the last full backup  and the last log backup for each database on each of the production servers using the system table "backupset" and related backup tables.


How to become root when your user is hardened?

I currently have a VM where the user is locked down and i am unable to find any flags. I have tried to use sudo but the account is not a sudoer. I have tried "nano /etc/sudoers" but i received a permission denied message. Any other ideas on how to become root?  Also, this is for a class. Its a basic CTF, and he completely locked down his VM it seems...


There is some sense in saying that the limit of $\ell^p$ norms  $\displaystyle \lim_{p \to \infty} \lVert x \rVert _p = \lVert x \rVert _{\infty}$  is uniform in $x$?  Maybe with this definition  $(\forall \varepsilon > 0)(\exists M>0)(\forall x \in \ell^q) \big( p>M \ \Longrightarrow \ | \ \lVert x \rVert_p - \lVert x \rVert_{\infty} \ | < \varepsilon \big)$  where $q \in [1, \infty)$ is fixed, and $p$ take values in $(q, \infty)$.  This is true? If not, someone have a counterexample?  Thanks


Can a brokerage hold BUY order from customer until brokerage has needed stock to fill the order "in-house"?

According to :  Internalization When you place an order to buy or sell a stock, your broker has choices on where to execute your order. Instead of routing your order to a market or market-makers for execution, your broker may fill the order from the firm's own inventory. This is called "internalization." In this way, your broker's firm may make money on the "spread" – which is the difference between the purchase price and the sale price.  So from this definition, I've understood that if a broker has a particular stock, it can fill it "in-house" instead of directing it to the open market. But can a broker hold the BUY order from the customer(one with a big possible spread), until the brokerage purchases needed stock from either its customers or open market and then fill the BUY order to gain the spread profit? I assume that the operation itself will be very fast(to buy the stock at market price) and, probably, not noticeable by a customer. Example: stock costs $100, some customer places an order to buy the stock for $400. A brokerage firm doesn't have the stock in inventory at the current time. Is it legal? Is it a common practice?


Why didn't Doctor Strange wind back the clock way before Thanos got any of the Infinity Stones?


Can different gauge wiring be used in the same circuit?

I am extending a lighting and outlet circuit in a basement. The current setup has the following characteristics   15 amp. circuit breaker (200 amp service) 4 existing lighting fixtures using CFL bulbs (~ 20 W each) 1 existing double duplex outlet box (no regular appliance in use) 14/2 and 14/3 NM cabling (lighting switched, outlets not) throughout less than 100 ft of cabling so far   I plan on adding three lighting fixtures (for LED spots, less than 20W each) and one duplex outlet. I will tap off one of the existing boxes to get both a switched and a constant hot line.  Additional cabling will be less than 30 ft.  Is there any reason I cannot use 12/2 and 12/3 NM cabling for this project (I happen to have some on hand)?    Is there any practical benefit (e.g., less voltage drop in this small section of line)? Is there any disadvantage in doing so, other than higher cost of cabling  and the slightly harder handling of thicker wires?    If the cabling were concealed, would the presence of a 12 gauge wire in an outlet box or fixture convey something to an electrician or future DIYer that is misleading based on the existence of unseen 14 gauge wiring upstream?


Interaction between charged particles through static electric fields

I generally find it pretty primitive to accept that static charges communicate with the help  of static electric fields without any exchange going on between them such as electromagnetic waves. I wanted to know whether there are any theories that put forth more detailed explanation for this kind of interaction using any wave picture.  I know that it has been postulated that charged particles radiate energy only when they are accelerated and I  do have few confusions regarding the necessity of the involvement of EM waves in static charge interaction but to shorten up the question I would like to ask the following question :  what is the relation between speed of EM radiation and electrostatic interaction ?


In ubuntu bash script how to remove space from one variable  string will be      3918912k    Want to remove all blank space.


Let $f: [0, 1]\rightarrow R$ be continuous and suppose that $f(0) = f(1)$. Prove there is $x$ such that $f(x)=f(x+\frac{1}{n})$

Let $f: [0, 1]\rightarrow R$ be continuous and suppose that $f(0) = f(1)$. Prove that for each positive integer $n$ there is an $x$ in $[0, 1 - \frac{1}{n}]$ such that $f(x) = f(x + \frac{1}{n}$). Without loss of generality, take $f(0)=f(1)=0$. I have been able to show that if $f(x)\ge 0$ or $f(x)\le 0$ the statement is true. It actually isn't that difficult to show. The trick is to define $g_n(x) = f(x+\frac{1}{n})-f(x)$, on $[0,1-\frac{1}{n}]$ then notice that $g(0)=f(\frac{1}{n})$ and $g(1-\frac{1}{n}) = -f(1-\frac{1}{n})$. We want to exclude the cases where $f(\frac{1}{n})=0$ and $f(1-\frac{1}{n})=0$ since that will immediately prove our statement. Using our condition $f(x)\ge 0$ and $f(x)\le 0$ and applying intermediate value theorem, we deduce that there's some $c$ such that $g_n(c)=0$. When we don't have the condition $f(x)\ge 0$ and $f(x)\le 0$, we could have continuous function such that $f(\frac{1}{n})\cdot f(1-\frac{1}{n}) = -|f(\frac{1}{n})\cdot f(1-\frac{1}{n})|$ (this is a long way of saying they have different sign). Notice that the method I described in the paragraph above can be extended to any interval $[a,b]$ if $b-a\ge \dfrac{1}{n}$. The main obstacle I face right now is that $f$ could have at least $n$ zeros such that the distance between any consecutive zeros the distance is at most $\frac{1}{n}$. However, I have struggled with this problem for a while now and I have made little progress. I would appreciate some hints, but please don't post complete solutions.


Why pressure is considered as scalar quantity?

Why is pressure is considered as a scalar quantity not a vector one while we know the pressure is force exerted on a specific unit area and vector is a quantity which is defined as a magnitude and a direction. It is not like any question asked before about scalar and vector quantities


What to read in History of Middle-earth?

I’m interested in reading some Lord of the Rings books but I’m wondering which ones to start with having to do with History of Middle-earth. Are they all important or can one just read The Silmarillion?


Is the result still true if we drop completeness?

I know how to prove the following exercise ( from Folland) :      If $X$, $Y$ are Banach spaces. $T:X\rightarrow Y$ is a linear map such that $f\circ T\in\operatorname{dual}(X)$ whenever $f\in \operatorname{dual}(Y)$, then $T$ is bounded.    Now I want to know whether the result is still true if $X$ and $Y$ are just normed vector spaces instead of Banach spaces.   Thank you so much.


Slight difference in definitions of Glassers Master Theorem

I’m probably misreading but there seems to be a slight difference in the definition of Glasser’s Master Theorem between  and .  The difference lies in the substitution $u$ and $\phi(x)$ with $u$ having $x - a - \sum$ over $x - \sum$.  Are these equivalent? Is there an error with one?


One might want to use a generic pronoun, that doesn't specify the gender of the person. Although "he" can be used in such case, they decide that "he" still reflect the history time when male was dominant. After searching in the internet, they find the .  The problem is, what they learnt in school is they only use for a group of people. Someone may not know the existence of the singular "they", so it can lead to misunderstanding. Especially when after the singular they, the verb doesn't change to reflect the singular form:     When I tell someone a joke they laughts laugh.   So they want to know how popular the singular they get known in modern English. Is it safe to use it without any note?   Ok, I am them


Write a file in a "resources" folder within Eclipse source

I have the following code to write a string on a file (relative path loaded):  void writeFile(String string){         try {             //ClassLoader classLoader = Thread.currentThread().getContextClassLoader();             ClassLoader classLoader = getClass().getClassLoader();             File newFile = new File(classLoader.getResource("conf/passwords.txt").getFile());              //Path of "passwords.txt" where it writes the info             System.out.println("ABSOLUTE PATH: " +newFile.getAbsolutePath());              FileWriter flux = new FileWriter(newFile);             BufferedWriter writer = new BufferedWriter (flux);             writer.write(string);              writer.close();         } catch (IOException e) {             System.out.println("ERROR on file writing.\n" +e.getMessage());             e.printStackTrace();         }     }   It works, but the string is not written on my original file that is located on the project path, as it follows: src/conf/passwords.txt  Instead of this, the string is saved on the following path: C:\Users\becario01\workspace.metadata.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\searchLef\WEB-INF\classes\conf\passwords.txt  I want to write the string on my original file, to show easily while I´m working on my workspace.   I would thank a lot any helpful reply.  Regards.


I am trying to change the icon of my Java application. Here is the structure of my project:  src    gui       FileCopyManager.java images     folder.png   Now I have the following code:  public class FileCopyManager extends JFrame{     public void changeIcon() {         this.setIconImage(new ImageIcon(Toolkit.getDefaultToolkit()                 .getClass().getResource("../../images/folder.png")).getImage());     }     public FileCopyManager() {         changeIcon();         this.setSize(800,600);         this.setVisible(true);     }     public static void main() {         new SwingUtilities.invokeLater(()->{             new FileCopyManager();         });     } }   However when I try to run this code I get a NullPointerException on the this.setIcon line.  Any ideas?


Solution check: Let $f_n$ be fibonacci numbers. Prove: $\sum_{k=0}^{n-1} \binom{n+k}{2k+1} = f_{2n-1}$ and $\sum_{k=0}^n \binom{n+k}{2k} = f_{2n}$

The question: Let $f_n$ be fibonacci numbers. Prove: $\sum_{k=0}^{n-1} \binom{n+k}{2k+1} = f_{2n-1}$ and $\sum_{k=0}^n \binom{n+k}{2k} = f_{2n}$  For every $n\in N$.  $f_0=f_1=1$, $f_n=f_{n-1}+f_{n-2}$ for $n\ge 2$  I'm supposed to do this through induction.  What I did, first, is that I've seen that for $1$ both statements are true, then assumed for $n$.  For $n+1$ I got that the first sum is equal to the first sum for $n$ and the second sum for $n$, which under the definition of fibonacci numbers, makes the assumption true.  Similarly I did the process for the second sum.  Is this all that I had to do to solve this problem? What's bugging me is that I need to use both of the sums for a certain $n$ in proving that either one of those sums is valid for $n+1$, which I haven't encountered yet in exercises containing induction.


What can I use to find duplicate photos, including photos that have been resized?


It is perhaps a bit embarrassing that while doing higher-level math, I have forgot some more fundamental concepts. I would like to ask whether the square root of a number includes both the positive and the negative square roots.  I know that for an equation $x^2 = 9$, the solution is $x = \pm 3$. But if simply given $\sqrt{9}$, does one assume that to mean only the positive root? And when simply talking about the square root of a number in general, would one be referring to both roots or just the positive one, when neither is specified?


Beginner Books to learn fuzzy set and fuzzy logic

I want to learn measures of possibility but first I need to learn Fuzzy Set/Logic, some book/material recommendations for beginners?


Accepting vs failing to accept the null hypothesis?

In  paper the authors state the following regarding a null hypothesis significance test:  If P-value < critical value, reject null hypothesis and accept the alternative hypothesis (difference detected). If P-value > critical value, accept null hypothesis (no difference is detected)  Have the authors made a mistake by saying 'accept the null'? I initially thought so but then I noticed in the abstract they state:  P value is condemned by one school of thought who claims that focusing more on P value undermines the generalizability and reproducibility of research.  So they are clearly aware of the issues with p-values. So why do they then say 'accept the null' instead of 'fail to reject the null'? Maybe its just a convention to say 'accept the null' even if one is aware that what we are really doing is failing to reject the null?


issue in Previous Button Navigation in ScreenFlow

<template>            <lightning-card>                     <lightning-input type="text" label="field1" name="field1" onchange={handleChange}></lightning-input>                     <lightning-input type="text" label="field2" name="field2" onchange={handleChange}></lightning-input>                     <lightning-input type="text" label="field3" name="field3" onchange={handleChange}></lightning-input>

{errorMsg}

                 </lightning-card>
         <lightning-button class="slds-m-left_x-small" label="Previous" onclick={handlePrevious}>         </lightning-button>         <lightning-button class="slds-m-left_x-small" label="Next" variant="brand" onclick={handleNext}>         </lightning-button>
 </template>  We have above lwc component, which is embedded in screenflow. and the screen flow previous,next buttons are overrided by using Flow Navigation Events. So when we clicked on Previous button, we are facing  class java.lang.String cannot be cast to class java.lang.Boolean (java.lang.String and java.lang.Boolean are in module java.base of loader 'bootstrap')


This app won't run without google play services, which are missing from your phone. it's asking me for a code for redeem, setting and or _________   please help me reinstall the google play services that was on the phone it an LG trac phone through page plus


Resistors in para and series circuit, finding volt

How anyone know how to do the question? I know how to reduce it to a window pane of 6/6/6/6 with a 3 in series but i have no idea how to do it.  Well i did manage to reduce the right side of the circuit to a pane of 6/6/6/6 and am unable to determine if its a Wye-Delta transformation (probably not) and I do not know which of the resistors are in parallel and which are in series.  Answer should be 4/3V   (The website which the answer was hosted initially no longer exists)


I want to start developing in Swift. I already own an apple developer account, yet am struggling to download Xcode (n) beta.  How can I do this?  Thank you in advance.


How can I take a picture with my webcam in Windows 7?

I know it existed as sort of a folder in Windows Explorer in at least Windows XP, but I just can't seem to find it in Windows 7...  How can I take a picture with my webcam in Windows 7 without using any 3rd party tools?


question on US Advance Passenger Information System

I have a question on this electronic APIS. If I fly from China to USA and book ticket and check in using Chinese passport, but enter USA using US passport, will this be a problem? I am concerned due the the information mismatch between APIS (immigration) and US passport, there will be a problem entering US?  thanks


after German residence permit expires, can I start my tourist 90/180 days?

I am an American studying abroad in Germany, but I want to spend up to 90 days as a tourist in Spain following the end of my program and the expiration of my residence permit.   I entered the Schengen zone on the grounds that I have US citizenship and can therefore enter without a visa and stay in Germany for up to 90 days while applying for a residence permit. However, I do not know if the two months that it took me to officially receive my residence permit count as ~60 out of the 90 days. I do know however that time passed within the period of the res permit does not count towards the 90 days, as other posts have pointed out.  The main thing I want to know is if my residence permit retroactively covers that two-month period that passed before I officially received it (I was already applying for it upon arrival, but it got delayed and so the sticker in my passport officially says the term is March-June, even though I arrived in January). If so, I would have never started an 180 day cycle and can therefore just make a stop in the UK and get a re-entry stamp to Spain to begin my 90 days as a tourist.


I have noticed that in both the 10k tools and in many Meta questions, 'rejected' migrations are referenced. What are they? How is one rejected? What happens?


WMI object to get current sessions with client name?

I want to be able to create a powershell script that will tell me, for all RDP sessions currently active on a machine, who the user is, and what their clientname (machine name) is.  I can use a combination of win32_loggedonnuser and win32_logonsession to get the username information, but I can't find the client name in these objects (enumerations?).   PS C:\> $logons = gwmi win32_loggedonuser; $lstring = ""; foreach($l in $logons) { $lstring +=$l;} $lstring -match "cephalopod"; False PS C:\> $sessions = gwmi win32_logonsession; $sstring = ""; foreach($s in $sessions) { $sstring +=$s;} $sstring -match "cephalopod"; False   (cephalopod is my machine name, the machine that's logged into the server box)  .  I can see that HKCU:\Volatile Environment does have the client name, and the temp key has the user name within it, but I can't establish from the keys alone if the session is currently active.  Am I missing an API call that will get me all this information in one place?  Basic requirement: grep out the Task Manager > Users listing for user and client name, where status is active.


Definition of Basis for the Neighborhood System

I'm trying to learn a bit about topology through independent study. I've been using Bert Mendelson's "Introduction to Topology - 3rd edition". I'm having a lot of fun but I'm a bit confused regarding definition 4.9 on pg 45. I will reproduce it hereafter:     Definition 4.9 - Let $a$ be a point in metric space $X$. A collection of neighborhoods $\mathcal{B}_a$ is called a basis for the neighborhood system at $a$ if every neighborhood $N$ of $a$ contains some element $B$ in $\mathcal{B}_a$.   Here is the source of my confusion, please correct me if I am wrong:   1) Every neighborhood of $a$ must contain $a$ it self, so shouldn’t any neighborhood of $a$ be automatically a basis of the neighborhood system at $a$?   2) If this is true (and I'm hoping it is false) what is the condition that forces $\mathcal{B}_a$ to grow beyond a trivial set such as $\mathcal{B}_a = \{a\}$?  Thank you.


Are there any differences between Java's "synchronized" and C#'s "lock"?

Do these two keywords have exactly the same effect, or is there something I should be aware of?


True seeing, can you see what you see past?

When under the effects of true seeing, and you see past illusions and stuff, do you still see the other forms? So lets say people were using illusions as advertising banners, could you see the banners?


Prove that lebesgue integrable equal lebesgue measure

Let $S$ be a bounded measurable subset of $\mathbb R$. Let $f \colon S  →  (0,\infty)$ be Lebesgue integrable. Prove that   $$\lim_{n\to\infty}\int_S\ f^{1/n} \;\mathrm{d}m = m(S)$$  Where $m(S)$ is the Lebesgue measure of $S$.  There is a hint that let $S = A \cup B$, where $A = f^{−1}((0, 1))$ and $B = f^{−1}([1,+\infty))$.   And the sequence of functions $h_n\ (n = 1, 2, 3, \dots),$ where $h_n(x) = ({f(x)})^{1/n}$.  I notice that $h_1(x)\leq h_2(x)\leq h_3(x) \leq \dots$   How can I apply monotone convergence theorem to the given hint.


Received an "Enlightened badge" and then had my answer unaccepted

Per the subject, I'm wondering if my enlightened badge will disappear (it hasn't yet, but my answer was only recently unaccepted). To be clear, I'm not worried about my badge or my answer being unaccepted (a different answer was accepted in my place that absolutely deserved it). I'm mainly just curious about how thorough Stack Exchange is with edge cases. In detail:   I posted this answer:  The answer was accepted pretty quickly. After it was accepted another answer was posted that answered the question even better A day later I received the enlightened badge A couple of hours later the other answer was accepted in my place.   I already had a couple of enlightened badges, and if I click on the badge to see the list of answers that I received it for I see this answer.  Clicking on that answer from the enlightened badge page brings me to my non-accepted answer. This begs the question: Will Stack Exchange remove the badge from my profile? I feel like it should.


Which is faster: Stack allocation or Heap allocation

This question may sound fairly elementary, but this is a debate I had with another developer I work with.  I was taking care to stack allocate things where I could, instead of heap allocating them. He was talking to me and watching over my shoulder and commented that it wasn't necessary because they are the same performance wise.  I was always under the impression that growing the stack was constant time, and heap allocation's performance depended on the current complexity of the heap for both allocation (finding a hole of the proper size) and de-allocating (collapsing holes to reduce fragmentation, as many standard library implementations take time to do this during deletes if I am not mistaken).  This strikes me as something that would probably be very compiler dependent. For this project in particular I am using a  compiler for the  architecture. Insight on this combination would be most helpful, but in general, for GCC, and MSVC++, what is the case? Is heap allocation not as high performing as stack allocation? Is there no difference? Or are the differences so minute it becomes pointless micro-optimization.