I have a wordpress website   mywebsite.net   on the wwww version www.mywebsite.net wordpress doesn't load  so  want that if the user open the www version of my website is redirect to the non-wwww version  here my .htaccess  # Do not remove this line or mod_rewrite rules and search engine friendly URLs will stop working RewriteBase /  # BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule>  # END WordPress  # Enable cross-domain CORS  <FilesMatch "\.(ttf|otf|woff)$"> <IfModule mod_headers.c>         Header set Access-Control-Allow-Origin "*" </IfModule> </FilesMatch>  # WordPress SEO - XML Sitemap Rewrite Fix <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^sitemap_index.xml$ /index.php?sitemap=1 [L] RewriteRule ^([^/]+?)-sitemap([0-9]+)?.xml$ /index.php?sitemap=$1&sitemap_n=$2 [L] </IfModule>

This question is here so we can offer users who are looking for information on how to make one or more common or basic redirects in Apache using the htaccess file. All future questions pertaining to finding information that is that is covered by the question should be closed as a duplication of this question. .  Whats the point in this question? The idea while not perfect is catch the most commonly asked questions regarding redirects using the  htaccess on the Apache platform either on  some type of lamp or a live server. The type of answers should be generally those that you could imagine are used by 100,000’s of sites world-wide and are constantly asked here at Pro Webmasters repeatedly over and over in various forms.  A few examples of the type of answers we are looking for:   How can I redirect non-www to www? How can I redirect a sub domain to the main domain? How can I redirect a sub folder from domain to a root or a subdomain?  How can I redirect an old URL to a new URL?   A few examples of the types of answers that we are not looking for:   Answers that do not involve a redirect. Any answers relating to NGinx, IIS or any other non-Apache platform. Answers that involve custom and complex string or query removals.   Resources for Advanced to Complex Mod_Rewrite Rules:      Please note: that this question is still in construction and may need some refining either by myself or a real moderator of Pro Webmasters, if you have any concerns or questions .


I think I'm overthinking it, but this p-value for the exp.c:anx.c interaction (3.84e-09) is significant, right? In other words, it's much smaller than 0.001? Irrational numbers are confusing for me, and I also have a negative t-value that is throwing me off.   I'm also confused at the bottom where it shows: p-value: < 2.2e-16, what does this mean? Overall for the model?

I have a problem with the interpretation of a test result in which the p-value is 8.6e-28. How should it be interpreted? What is the e for?  Specifically, I used White's Test for the homoscedasticity assumption of a linear regression:  White's general test statistic :  150.0535  Chi-sq( 9)  P-value =  8.6e-28


I dont see how we can find the length of an object. For arrays i can your array.length but it doesnt work for objects, any suggestions?  Thanks!

I have a JavaScript object. Is there a built-in or accepted best practice way to get the length of this object? const myObject = new Object(); myObject["firstname"] = "Gareth"; myObject["lastname"] = "Simpson"; myObject["age"] = 21;


I was using blender and i accidentally closed the menu on the right and i cannot get it open. It appears there is no button or shortcut to open it from the search menu. Any help? Ive done so much and i dont want to restart it.

I can't find a way to close a view panel, in particular the horizontal at the bottom, is pretty useless to me at this moment.


When you visit your user page at https://stackexchange.com/users/<ID>/<NAME> (note HTTPS, secure connection), the links (e.g., top questions and answers) take you to the HTTP (not HTTPS!) locations.  My experience with other sites created an expectation that once I land in a secure area, I only leave it by an explicit request and with a warning, so the current behavior looks like a bug to me.  It appears that I am not the first to notice this shortcoming. Other sites appear to make faster progress on this. SE is the premier technology site on the internet, and it seems to be struggling with a technical issue for years. Isn't this weird?  Related:

The links to other StackExchange sites in User profile -> Summary -> Accounts don't use https when the User profile was accessed using https.


For $\mathcal L = -\frac14 F_{\mu\nu}F^{\mu\nu}$ I would appreciate some help evaluating  $$\frac{\partial \mathcal L}{\partial(\partial_{\mu}A_{\nu})}.$$  I've found  $$\frac{\partial \mathcal L}{\partial(\partial_{\mu}A_{\nu})} = -\frac14\frac{\partial}{\partial(\partial_{\mu}A_{\nu})}(\partial_{\lambda}A_{\sigma} - \partial_{\sigma} A_{\lambda})(\partial_{\lambda} A_{\sigma} - \partial_{\sigma} A_{\lambda}) $$  $$ = -\frac14 \frac{\partial}{\partial(\partial_{\mu}A_{\nu})} \left( 2\partial_{\lambda}A_{\sigma}-2\partial_{\lambda}A_{\sigma}\partial_{\sigma}A_{\lambda}\right)$$ $$ = -\frac14 4\left(\partial_{\nu} A_{\mu} - \partial_{\mu} A_{\nu}\right) \qquad(*)   $$ $$ = F_{\mu\nu}$$  but I cannot understand the step taken to get to $(*)$. In my attempt, I take the chain rule to obtain   $$\frac{\partial \mathcal L}{\partial(\partial_{\mu}A_{\nu})} = -\frac12 F_{\mu\nu} \frac{\partial(\partial_{\alpha}A_{\beta} - \partial_{\beta} A_{\lambda})}{\partial(\partial_{\mu} A_{\nu})}$$  $$= -\frac12 F_{\mu\nu}(1) - \frac12 F_{\mu\nu} \frac{\partial(\partial_{\beta}A_{\lambda})}{\partial(\partial_{\mu}A_{\nu})}$$ $$ = -\frac12 F_{\mu\nu} - \frac12F_{\mu\nu}\delta_{\beta\mu} \delta_{\lambda\nu} = -\frac12 F_{\mu\nu} - \frac12 F_{\beta\lambda}$$  which seems to give me almost what I want, but I must have run into an error because this expression no longer makes sense, as each term should be indexed by $\mu,\nu$.   So my 2 questions are: how do we get to $(*)$ and where did my attempt go wrong?

I've started reading Peskin and Schroeder on my own time, and I'm a bit confused about how to obtain Maxwell's equations from the (source-free) lagrangian density $L = -\frac{1}{4}F_{\mu\nu}F^{\mu\nu}$ (where $F^{\mu\nu} = \partial^\mu A^\nu - \partial^\nu A^\mu$ is the field tensor).  Substituting in for the definition of the field tensor yields $L = -\frac{1}{2}[(\partial_\mu A_\nu)(\partial^\mu A^\nu) - (\partial_\mu A_\nu)(\partial^\nu A^\mu)]$.  I know I should be using $A^\mu$ as the dynamical variable in the Euler-Lagrange equations, which become $\frac{\partial L}{\partial A_\mu} - \partial_\mu\frac{\partial L}{\partial(\partial_\mu A_\nu)} = - \partial_\mu\frac{\partial L}{\partial(\partial_\mu A_\nu)}$, but I'm confused about how to proceed from here.  I know I should end up with $\partial_\mu F^{\mu\nu} = 0$, but I don't quite see why.  Since $\mu$ and $\nu$ are dummy indices, I should be able to change them: how do the indices in the lagrangian relate to the indices in the derivatives in the Euler-Lagrange equations?


I have about 500 threads that I want them to run simultaneously. I read that the default glibc allows only about 300 threads to run simultaneously. How did they got to this number? (I'm on 32 bit system)

What is the maximum number of threads that can be created by a process under Linux?  How (if possible) can this value be modified?


After pumping both the tires equally, after a  few weeks pass, the rear tire of my bicycle keeps on getting flatter day by day, and looses pressure. I have checked everything and there is no leakage anywhere.  Why always does it effect rear wheel?

I rode my road bike on Friday and the tyres were at the correct pressure then, around 100psi.  On Tuesday, I jumped on without checking them and quickly realised something was wrong with the rear tyre.  It wasn't completely flat but was fairly soft.  I hadn't gone far so went home and took the car to work instead.  When I got home later, I was surprised to find the tyre, while still soft, hadn't lost all pressure by any means.  It was around 40psi and felt the same as when I left it in the morning.  I decided there must be a slow leak somewhere, but I couldn't find one anywhere, putting the inner under water and going around it methodically looking for bubbles.  I've never failed to find a leak before that way.  I've switched it out anyway because I don't want to mess around with my commute, but I'm curious ... is there another explanation for that amount of pressure loss?  Or must there have been a puncture somewhere that I missed somehow?  The tyres (whole bike) are pretty new and in excellent condition.


A couple of days ago I decided to install Ubuntu on my computer that runs Windows 8.1. I downloaded LiLi USB Creator, ubuntu-14.10-desktop-amd64.iso, and used it to create a 100Gb partition and install Ubuntu there.  Everything went fine, I was able to reboot, install Java JDK, and other stuff. When I went into Windows again and back to Ubuntu I got the dreaded Low Graphics Mode error, and I couldn't reach the login screen.  I tried entering fail safe mode and install drivers for my AMD GPU using sudo apt-get install fglrx.  I tried editing the /etc/lightdm/lightdm.conf file because I read something about a bug, but this file was not present in the mentioned folder.  I tried switching from lightdm to gdm using . Nothing worked, so I reinstalled the same version of Ubuntu. The same thing happened again, without me changing/installing anything or entering Windows in between. I tried installing everything again. I tried updating my programs using some GUI in the sidebar as well as using sudo apt-get update && sudo apt-get upgrade.  I tried installing the 14.04.2 LTS version instead. When trying to install drivers using fglrx in this version, it complains about dependencies.  After some installations I'm able to reach the login GUI a couple of times, and after some I go directly to the graphics error. I have done so many re-installations and tried so many things in so many orders that my head is about to explode.  Is there something I should reconfigure in my BIOS? Does my 2x AMD 280x GPUs in crossfire have anything to do with it?  Can someone more experienced than me help me to troubleshoot this?  EDIT: I've mainly used  when trying to troubleshoot. I've tried most of the things that I've found relevant. The post is also quite old, and some of the solutions are out-dated. I also have a problem that I haven't seen anywhere else: The error occurs randomly after a fresh installation. That is why I've created my own post about the problem.

Note: This is an attempt to create a canonical question that covers all instances of "low-graphics mode" error that occurs to a user, including but not limited to installation of wrong drivers, incorrect or invalid lightdm greeters, low disk space, incorrect installation of graphics card like ATI and Nvidia, incorrect configuration of xorg.conf file while setting up multiple monitors among others. If you are experiencing the "low-graphics mode" error when trying to login but none of the following answers work for you, please do ask a new question and then update the answers of this canonical question as and when your new question gets answered.   When I try to boot into my computer, I am getting this error:  The system is running in low-graphics mode Your screen, graphics cards, and input device settings could not be detected correctly. You will need to configure these yourself.   How do I fix the failsafe X mode and login into my computer?  Answer index:


The Player's Handbook states (emphasis mine):  An incapacitated creature can’t take actions or reactions.  Suppose I am fighting a creature that has a multiattack, and I have an ability that can incapacitate a creature as a reaction. If the creature has completed the first attack in its multiattack, could I prevent the remainder of its attacks with my ability? Or is it too late, since the remaining attacks aren't actions?

Suppose Alex is a fighter with the Extra Attacks feature, so each time they take the Attack action they can make two attacks. Alex attacks Sam, a Fighter/Monk with access to the Riposte Battle Master maneuver and the Stunning Strike monk feature.   Here's what happens:   Alex takes Attack as their action for the turn. Alex makes their first attack against Sam and misses. Sam uses their reaction and Riposte (spending a superiority die) to attack Alex. Sam hits. Sam spends a ki point to activate Stunning Strike. Alex attempts a Con save and fails. Alex is now stunned.    It's still Alex's turn. They are stunned and thus cannot take actions. Can they make their second attack?   On one hand, Alex isn't taking an action to make their second attack; they have already taken their action and still have part of it left to resolve.  On the other hand, the effects of being stunned could be read as meaning that a stunned character stops taking actions, so any in-progress actions don't continue.        Riposte       When a creature misses you with a melee attack, you can use your   reaction and expend one superiority die to make a melee weapon attack   against the creature. If you hit, you add the superiority die to the   attack's damage roll.   (PHB, p. 74)     Stunning Strike      Starting at 5th level, you can interfere with the flow of ki in an   opponent’s body. When you hit another creature with a melee weapon   attack, you can spend 1 ki point to attempt a stunning strike. The   target must succeed on a Constitution saving throw or be stunned until   the end of your next turn.   (PHB, p. 79)     Stunned         A stunned creature is incapacitated (see the condition), can’t move,    and can speak only falteringly.    The creature automatically fails Strength and Dexterity saving throws.    Attack rolls against the    creature have advantage.      (PHB, p.292)


I got a file with some params of a script:  foo1 a b c foo2 a b c foo3 a b c   I need to run a script once for each line in this file passing the line as script arg, so it should do:  ./MyScript.sh foo1 a b c ./MyScript.sh foo2 a b c ./MyScript.sh foo3 a b c   How can I achieve this using Bash?

I have a text file that has a list of paths to various files. Is there a command I can use that will iterate through each line and delete the file at the stated path?


I'm currently learning Python, and don't know a whole lot- so I need somebody experienced to help me out here.  The code is this:  usernum = input('Enter a number, Ill determine if its pos, neg, OR Zero.') if usernum < 0:     print("Your number is negative.") if usernum > 0:     print("Your number is positive.") if usernum == 0:     print("Your number is zero.")   The error is this:  Traceback (most recent call last):   File "C:\Users\Admin\Documents\Test.py", line 2, in <module>     if usernum < 0: TypeError: '<' not supported between instances of 'str' and 'int'

In Python, how can I parse a numeric string like "545.2222" to its corresponding float value, 545.2222? Or parse the string "31" to an integer, 31?  I just want to know how to parse a float str to a float, and (separately) an int str to an int.


Says I have a link, which contains the ID = 19963307  Type 1 :   http://stackoverflow.com/questions/19963307/how-to-install-asp-net-mvc-5-on-a-server   Type 2 :   http://stackoverflow.com/questions/how-to-install-asp-net-mvc-5-on-a-server-19963307   Which one of the above links is better for SEO, or are they the same?

I would like to know what's the best location for an ID in a SEO optimized URL:   http://www.example.com/123/slug-title  http://www.example.com/slug-title-123


how to integrate $\int_{-\infty}^\infty\frac{dx}{x^2(1+e^x)}$?  How can I integrate this difficult form of integration, I tried many times to solve it by parts or by substitution but I didn't get it.

Essentially, all is in the title: Is it possible to compute the integral $$\int_1^{+ \infty} \frac{dx}{x^2(1+e^x)} \hspace{1cm} ?$$  I suspected some relation with a , but I was not able to find something explicit.


Whats the best but simplest way to add water mark using DPP4?  I cant find anything to create and save watermarks to use.

I recently downloaded Canon's DPP (Digital Photo Professional) 4. After the new UI improvements, and better algorithms that are incorporated into the new DPP 4, I thought I would give it a try and started using it. Everything looks good and easily understandable in DPP4 except one thing: adding watermark onto the photo? This option is available with Adobe Lightroom, but I'm not sure if DPP has this option or not.  Could anyone confirm whether DPP has this option? If it does, then how I do I put an image watermark when I'm editing in DPP 4?


Pressing ctrl+esc opens the windows start menu.. I'd like to disable this shortcut but still have normal functionality of ctrl and esc individually. Is this possible?

I am a Windows 7 user that spends 80% of my time in gvim, with caps remapped to escape.  Just recently I have started hitting Ctrl-escape (well, Ctrl-Caps) by mistake, which pops up the start menu. This then requires and awkward escape > Alt-Tab > Alt-Shift-Tab combo to get back to gvim.  Is there a way to disable this shortcut?


we are asked by our prof. to make a code of a game in eclipse and we chose tic tac toe but i can't get it to play properly. when i run the program i can still change from x to o and not get a winner.  here's my code:  private void winningGame() {     String b1 = btn1.getText();     String b2 = btn2.getText();     String b3 = btn3.getText();     String b4 = btn4.getText();     String b5 = btn5.getText();     String b6 = btn6.getText();     String b7 = btn7.getText();     String b8 = btn8.getText();     String b9 = btn9.getText();      //////Player X Winning Combination//////      if (b1==("X")&& b2==("X") && b3==("X"))     {         JOptionPane.showMessageDialog(null, "Player X wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         xCount++;         gameScore();     }     if (b4==("X")&& b5==("X") && b6==("X"))     {         JOptionPane.showMessageDialog(null, "Player X wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         xCount++;         gameScore();     }     if (b7==("X")&& b8==("X") && b9==("X"))     {         JOptionPane.showMessageDialog(null, "Player X wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         xCount++;         gameScore();     }     if (b1==("X")&& b4==("X") && b7==("X"))     {         JOptionPane.showMessageDialog(null, "Player X wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         xCount++;         gameScore();     }     if (b2==("X")&& b5==("X") && b8==("X"))     {         JOptionPane.showMessageDialog(null, "Player X wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         xCount++;         gameScore();     }     if (b3==("X")&& b6==("X") && b9==("X"))     {         JOptionPane.showMessageDialog(null, "Player X wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         xCount++;         gameScore();     }      ////////Player O Winning Combination//////////      if (b1==("O")&& b2==("O") && b3==("O"))     {         JOptionPane.showMessageDialog(null, "Player O wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         oCount++;         gameScore();     }     if (b4==("O")&& b5==("O") && b6==("O"))     {         JOptionPane.showMessageDialog(null, "Player O wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         oCount++;         gameScore();     }     if (b7==("O")&& b8==("O") && b9==("O"))     {         JOptionPane.showMessageDialog(null, "Player O wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         oCount++;         gameScore();     }     if (b1==("O")&& b4==("O") && b7==("O"))     {         JOptionPane.showMessageDialog(null, "Player O wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         oCount++;         gameScore();     }     if (b2==("O")&& b5==("O") && b8==("O"))     {         JOptionPane.showMessageDialog(null, "Player O wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         oCount++;         gameScore();     }     if (b3==("O")&& b6==("O") && b9==("O"))     {         JOptionPane.showMessageDialog(null, "Player O wins","Tic Tac Toe", JOptionPane.INFORMATION_MESSAGE);         oCount++;         gameScore();     }     }  ////////Methods//////// private void gameScore() { txtCountX.setText(String.valueOf(xCount++)); txtCountO.setText(String.valueOf(oCount++)); }  private void choosePlayer() { if(start.equalsIgnoreCase("X")) { start = "0"; } else { start = "X"; }  }   everything from the reset to the other functions are working . The only problem is i can't get a winner and also the result or the score. and the debugger says it's in these lines of codes. more acccurately on the winningGame().

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I noticed that I lost 40 reputation points on Stack Overflow today. I checked my reputation history and this is the reason it gave me:     -10   19 mins ago     removed     User was removed      -30   19 mins ago     removed     Where is Visual Studio Express?   I did answer a question about where Visual Studio was located about a week or so ago, but I can't find it now.   I'm guessing that the original person who asked the question deleted his account and so all his questions got deleted as well, but why remove the reputation on the answer?

Possible Duplicate:          There is a weird scenario I came across, I that know if you earn reputation and the user deletes the question the reputation remains.  However on 22nd of June, I answered a question and it was accepted. Today I found out that the question was deleted along with the user (couldn't find the user or any of his questions) and the reputation I earned is also gone.  I know this is not the expected behavior, but can I get the my reputation points back?


In an exam I have been asked to discuss the convergence of a series regarding a parameter $d$. Here's the following : $\sum_{n=0}^\infty \frac{(n!)^d}{(d\cdot n)!}$   The answer is that this series converges for $d \geq 2$. I totally understand that if $d \leq 1$, the series will not converge but I am blocked while trying to use the d'Alembert or Cauchy's rules.   Can somebody give me a tip ?

How can we find the general formula about the convergence of the serie $\sum_{n=0}^\infty \frac{(n!)^d}{(dn)!}$ for all $d\geq2$ ?  I tried using the d'Alembert Criteria but it doesn't simplify itself enough to prove the convergence.


I have a thread with some parser of an array. I have an array of String splitted by white-spaces from other String, cleared empty fields and now I am trying to clear all colons and equals from it. So I have created method that uses for-each with 'String s' in that array. Than I have another for-each with 'char c' in that String converted to char array. And here's that exception. Here's the code:      public String[] clearColons(String[] in) {             List<String> output = new ArrayList<>();              for (String s : in) {                     StringBuilder out = new StringBuilder();                      for (char c : s.toCharArray()) {                         if (c != ':' && c != '=') {                                 out.append(c);                         }                     }                      output.add(out.toString());             }              return output.toArray(in);         }   Please help!

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


Someone commented on an answer I've written, and I noticed there was a "1 more comment" message. I clicked on it, and saw the comment. I even replied.  A couple of minutes later I'm seeing a red [1] over my "inbox", and the comment is what I'm notified about.  Comments with which I've known to have interacted - e.g. by clicking "more comments" or by replying below them - should be considered as not requiring notification.

The notification area in the top-left notifies you when there is a comment posted on your question or answer. However, if you're already on that page and click the "add / show 1 more comment" button, the notification stays there until you click it to dismiss it, even though you've already read the comment.  My suggestion would be for clicking the "add / show n more comments" button to denotify all watched comments that it displays.


I disabled password for login at User Account setting, and later when I ran sudo, I get "Sorry, try again." It seems my previous password doesn't work anymore. I also tried hitting enter directly but it didn't work either.   I attempted to change the root password by following this article: .  Everything works fine, I did have got the "update password successfully" message. However, when I get back to the graphic desktop and tried to sudo anything, the new password didn't get me any more luck.   I repeated the process three more times and made sure there is no typo in setting new password.  I also tried to remove sudo requirement by following this article:   after resetting password in grub mode, but that didn't help.   So right now the OS works fine but I can't do sudo anymore or authenticate anything at all.  Any help will be appreciated!    So appearantly sudo asks for the user's instead of the root password, I guess that's while changing root password doesn't help. (Please correct me if that's not exact). However, I still can't find anything to get sudo to work after trying every single password I ever set up..

$ ls -l /usr/bin/sudo -rwsr-xr-x 1 root root 136808 Jul  4  2017 /usr/bin/sudo   so sudo is runnable by any user, and any user who runs sudo will have root as the effective user ID of the process because the set-user-id bit of /usr/bin/sudo is set.  From      the most visible difference between sudo and su is that sudo requires the user's password and su requires root's password.    Which user's password does sudo asks for? Is it the user represented by the real user ID of the process?   If yes, doesn't any user can gain the superuser privilege by running sudo and then providing their own password? Can Linux restrict that on some users? Is it correct thatsudo asks for the password after execve() starts to execute main() of /usr/bin/sudo?  Since the euid of the process has been changed to root (because the set-user-id bit of /usr/bin/sudo is set), what is the point of sudo asking for password later?   Thanks.  I have read , but it doesn't answer the questions above.


Help!  I have a 3 x 5 ft banner I'm making but I'm not sure about the photograph they want included.  How do I know if the photograph will work?  Need advice ASAP!  From resolution to size of image...

For wall-sized graphics and large banners (e.g. 3m × 5m), what is an acceptable PPI for print? As I understand it 300 ppi is the typical for 'small' artworks (esp. for clean text resolution). However, for small artworks, the audience usually engages at a much closer distance. Therefore, in the interests of keeping a bitmap file down to a reasonable size, can you get away with a much-reduced PPI for a large format/banner print?


Video and music editing software that can be used on Ubuntu 14.04? I installed Kdenlive, and seems to work okay, except that it tends to slow down the system a little. It also takes a bit of time to get your head around it. But I was wondering if there were other alternatives that I should try out as well.

What video editing software would you recommend on Ubuntu (or Linux in general) and why?  It can be for either beginners or experienced users.  Please only place one piece of software per response and include details to what makes it great!


My first thought was to try a contradiction; So given n is prime assume p is not prime i.e $p = p_{1}^{\alpha1} .... p_{r}^{\alpha r}$. But i didnt know where to go from there.

I have been researching  so I can write a program that finds them. A Mersenne prime looks like $2^n-1$. When calculating them, I have noticed that the $n$ value always appears to be odd. Is there confirmation or proof of this being true?


I have tags with asterisks in my favorites, like c#-* and *xaml*, in addition to normal tags like c# and wpf. Previously they worked correctly in the new navigation, but now they cause a couple of issues in the :   Questions are filtered by all tags (for example, questions with just c#-4.0 tag are included), but only tags without asterisks are displayed in the filter editor, page title and filter dropdown.  Expected: all tags are displayed the filter editor, page title and filter dropdown. Questions which are included based on the tags with asterisks are highlighted, other questions are not.  Expected: no questions are highlighted, because all of them are included in the filter.

In this case I'm filtering by the tag [tag:css*], but it's showing this as [css*] and showing the  tag's exerpt.


I am trying to fetch some data on my android validation using Facebook API. I am able to login into my facebook account. This is the permission I have set to fetch data from Facebook account  loginButton.setReadPermissions(Arrays.asList( "public_profile", "email", "user_birthday", "user_friends"));   using the above permissions I am trying to fetch profile name and other data I am getting a null pointer exception with the below code snippet  public void getFacebookData(AccessToken accessToken, Profile profile) {         System.out.println("---------------------");         System.out.println("--Facebook Login Successful!");         System.out.println("--Logged in user Details : ");         System.out.println("---------------------");         System.out.println("--User ID : " + accessToken.getUserId());         System.out.println("--Authentication Token : " + accessToken.getToken());         System.out.println("---------------------");         System.out.println("--First Name : " + profile.getFirstName());         System.out.println("--Last Name : " + profile.getLastName());         System.out.println("--URL Perfil: " + profile.getLinkUri());         System.out.println("--URL Imagem: " + profile.getProfilePictureUri(500, 500));         System.out.println("---------------------");         System.out.println("--ID : " + profile.getId());         System.out.println("--Name : " + profile.getName());         System.out.println("---------------------");          TextView profile_name = (TextView)findViewById(R.id.profile);         profile_name.setText(profile.getName());   Please, what be wrong with the approach I am using.


I'm from programmer background.  I would like to mimic the color scheme used in most Google Android app such as GMail, Google Analytic, to use them in my own app.      Those color looks   Elegant Harmony Comfortable   I was wondering, usually, for a designer, how does they generate such color scheme?

I'm a web developer, started to become a web designer. However, I think my understanding of colors is not practical yet. There are tools out there that can give you color harmonies, and more stuff, like , but they don't give you the start point. I mean, how should I know that for this web site, I'd better use green and for that website, choose red. How should I know that?  I think color selection is more like an art, instead of being a science, and I'm like "you should become an color artist, in order to become a web designer".  How can I improve my color selection skill?


I have 2 languages installed, normally I switch between them using CTRL + SHIF combination of keys. I updated few months ago Ubuntu to 17.10 and now I can't work in my IDE or other programs where I use CTRL + SHIFT + [SOME_KEY], because in 17.10 handles it the wrong way. Where as previously (in 17.04), I didn't have such problems. So, basically in the programs I can't use CTRL + SHIFT + F for example, it just switches the languages.  P.S. Please, don't propose the solution to change the combination of keys to switch the language.

I use Ctrl+Shift to change keyboard layout and Ctrl+Shift+v in terminal. It never was a problem with Unity but now Ctrl+Shift immediately changes language so that I can't use it for other shortcuts. Is there a way to solve this for GNOME without changing those shortcuts?


For the sake of simplicity I posted an anonymous question on a Stack Exchange site yesterday. Is there a way to "un-anonymize" the posted question by linking it to an account that will be created (To answer comments and stuff for example)? Since I have given my mail when creating the question, it should be possible right? (I got a mail telling me that I could do it, but when registering, the question still wasn't linked with my account, weirdly. )   does not solve my problem, as it does not work on beta boards (Or at least on some specific boards).

I asked a question and mistakenly created an unregistered user. Now I'm unable to access the question and respond to people answering it.  I have created a stack exchange user - how can I gain access to the unregistered account, and preferably move the question to my stack exchange user?


I have a problem. I have a .deb file for my ubuntu app, but I want users to be able to install it using the sudo apt-get install  command. How would I make it so that anyone can install my .deb file with sudo apt-get install?

As a developer of free software, I want to get my application into Ubuntu.  Should I provide a source tarball and ask for packaging? Or should I create a package myself? Should I target Ubuntu directly, or should I try to get into Debian and then into Ubuntu automatically?


There is a concept in computer science which deals with how to demonstrate negative binary numbers. Two methods for achieving this goal are  and .  Since I got acquainted with these methods, this question never stops coming to my mind that why the apostrophe is placed differently in ones' vs two's? I also saw many articles using one's instead. Even Google suggests that I might be mistaken!    So I want to resolve this issue once and for all. Is it a stylistic preference? What causes this difference? And please provide more examples of similar usage.

Why does the place of the apostrophes differ in the following two titles?   en.wikipedia.org/wiki/Two's_complement en.wikipedia.org/wiki/Ones'_complement   Which one is the correct?


Because of price, instead of taking a flight to Berlin, I have had a flight to Prague booked, and will take a bus to Germany. I am aware that a travel insurance is necessary as a tourist in Czech Republic, or I will have to pay a fine, but is that also the case for entering the country? As far as I am aware we will not be staying in Prague; our time in Czech Republic will be 5 hours or less.

For nationals that request the Schengen visa, the traveller must have insurance that covers, for a minimum of €30,000, any expenses incurred as a result of emergency medical treatment or repatriation for health reasons.  But what about citizens of 'Annex II' countries and territories (Japan, Brazil, etc)? Are they also required to have such insurance?


I’ve recently noticed that many of my posts get edited by new users, and the edits are subsequently approved (often unanimously).  Great, right?  Yes. Except that many of these edits are spurious, or wrong. The first kind irks me somewhat but is tolerable. The second kind, not so much.  Here are two examples from the last day:    – The edit doesn’t invalidate the answer, it’s just completely superfluous. I don’t particularly resent it, I just think it shouldn’t have been approved: that’s not what edits are for.  – The editor apparently confused the words “expect” and “except”. No biggie, but all but one reviewer didn’t notice this.   That’s not review. It’s just clicking “ok”.  I realise that there are already measures in place to catch  reviewers. But they don’t seem to be working particularly well, at least as far as I can tell.  I have no solution. I just wanted to offer this anecdote for consideration.

Already I have lost all hope of looking at late answers etc. It's just a parade of meh. I can't make any kind of intelligent decision because I can't see the other answers to the question, for instance. There's no Looks Good, only Skip, and those feel different to me. So I've been more interested in .  But people keep approving crap while I'm looking at it. Two or three "the post was already approved; please visit to edit" and I'm just "screw this whole thing".  Can we do something like one reject bounces all existing votes: you need three approves in a row? Because a lot of people are stupidly approving and actually driving me away from the queue.    Note this is less about letting bad edits through and more about keeping reviewers motivated.


precision = 2 number = 31684.28 result = Decimal(number) - Decimal(10 ** -precision) print(result)  Desired output: 31684.27  Actual output: 31684.26999999999883584657356  What I try to do is to subtract 0.01 from number.

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


Consider the matrix: $A = \pmatrix{-1&1 \\1&-1 \\ 0& 0}$ For this matrix, it is easy to see that no linear combination of its columns will yield a positive vector $b$ (namely, where $b_i > 0,  \forall i$). For other matrices, it is easy to see that there exists some linear combination that will yield a desired $b$. I am interested in the general case: How do I prove whether or not a given matrix $A \in \mathbb{R}^{m \times n}$ ($m > n$) can yield a linear combination that is positive? Note that there are no constraints on the linear combination - I am looking for any $x$ such that $Ax = b, \forall i, b_i > 0$ The  seems relevant, but I can't find exactly how to exploit it for this use case.

Given a matrix $A$ in $\mathbb R^{m\times n}$, if I want to know whether or not there is an $x \in \mathbb R^{n}$ such that  $$ Ax > 0, $$ (meaning all elements in $Ax$ are positive). Is there some easy way to verify whether or not such $x$ exists?


We already know that continuous image of path-connected spaces are path-connceted. I was thinking if the same result is true when we replace path - connected with locally path - connceted.  I think I have proved this for a continuous and open map.     Is the openness requirement necessary or continuity is enough (and simply I was not able to prove the statement in that case)?   More precisely, this is what I proved: suppose $f:X \to Y$ is a continuous and open map. Let $a=f(x) \in f(X)$ and let $J$ be a neighborhood bases for $x$ of path- connected spaces. Then $J'=\{f(A): A \in J\}$ is a neighborhood bases for $a$ of path- connected spaces. The openness of $f$ helped me to say that $A$ neighborhood of $x$ implies $f(A)$ neighborhood of $a$. The continuity of $f$ implies that $f(A)$ is path - connceted whenever $A$ is path - connected. Finally, if $U$ is a neighborhood of $a$ then $f^{-1}(U)$ is a neighborhood of $x$ and then there is $A\in J: A\subseteq f^{-1}(U)$, then $a \in f(A) \subseteq U$.

The question is pretty much in the title, I'm looking for an example of a locally connected space and continuous mapping such that the image is not locally connected.  Thanks!  EDIT: Corrected the phrasing to the intended meaning.


Been thinking about this one for awhile and I'm still stuck...  Thought about proving it by arriving at a contradiction but I haven't reached anything noteworthy.  If you do a proof by contradiction, you're assuming that you have an infinite poset that does not contain an infinite chain and infinite totally unordered set but I don't know how that helps me :(

Let $(X, \leq)$ be an infinite poset. Prove that there is an infinite $X' \subset X$ for which holds one of the following:  1) Induced order on $X'$ is linear.  2) $(X', \leq_\mathrm{ind})$ is antichain. (Every two elements in $X'$ are incomparable)    My attempt:  Let's start trying to construct a linearly ordered set $(X', \leq_\mathrm{ind})$ element by element. First we take some element $x_1 \in X$, then we take another $x_2 \in X$ such as $x_1 \leq x_2$ or $x_2 \leq x_1$. Basically, we take an element from $X$, if it is "good" we put it in our chain, otherwise we throw it away. We continue constructing the chain that way. If we do not stop at some finite step, then we are done, we have constructed linearly ordered subset.  If we do stop at some $x_n$ that means that we have finite amount of comparable elements, which means that $X \setminus X'$ is an antichain.    a) I am not sure about the soundness in the last step, could somebody please check it?  b) Can this be proved without a choice function?


Is the following equality correct?  $$\int_{a}^{b} f(x)\,dx = - \int_{b}^{a} f(x)\,dx.$$  I think I have already seen it before (I don't remember exactly where), but I can't find nothing about it in the internet. If the answer is yes, can you show the proof?

Let us define a very simple integral:   $f(x) = \int_{a}^{b}{x}$    for $a,b\ge 0$.  Why do we have the identity $\int_{a}^{b}{x} = -\int_{b}^{a}{x}$?  I drew the graphs and thought about it but to me integration, at least in two-dimensions, is just taking the area underneath a curve so why does it matter which direction you take the sum?


Assume $y$ is a Gaussian random variable with $\text{Var}(y)= \sigma_y^2=\sum_i a_i^2\sigma_i^2$, where $\sigma_i$ corresponds to $x_i$, all $x_i$ are independent. $\mu_y = \sum a_i\mu_i$. I want to derive a formula for $\text{Cov}(y,x_i)$. I have tried the following: $\text{Cov}(y,x_i) = \mathbb{E}[x_iy] - \mathbb{E}[x_i]\mathbb{E}[y]$. The last term is trivial to get. $\mathbb{E}[x_iy] \approx \mathbb{E}_z[\int \exp[-.5 (((x - \mu_i)^2)/\sigma_i ^2 + ((z/x - \mu_y)^2)/\sigma_y^2 )]/|x| dx]$, which is untractable I am afraind. So, I am wondering if there is a way to tackle this problem?

I think the following two formulas are true:  $$ \mathrm{Var}(aX)=a^2  \mathrm{Var}(X) $$ while a is a constant number $$ \mathrm{Var}(X + Y)=\mathrm{Var}(X)+\mathrm{Var}(Y) $$ if $X$, $Y$ are independent  However, I am not sure what is wrong with the below:  $$\mathrm{Var}(2X) = \mathrm{Var}(X+X) = \mathrm{Var}(X) + \mathrm{Var}(X) $$ which does not equal to $2^2 \mathrm{Var}(X)$, i.e. $4\mathrm{Var}(X)$.  If it is assumed that $X$ is the sample taken from a population, I think we can always assume $X$ to be independent from the other $X$s.  So what is wrong with my confusion?


I got $(a,b) \to a$, $(a,b) \to b$ and $(a,b) \to 0$ these mappings to be homomorphisms just by hit and trial. So when I looked for it's solution, these were the ONLY homomorphisms from  $ \Bbb Z$  $\oplus$ $\Bbb Z $ to $\Bbb Z$.  There was a hint, which is as follows: "Observe that an idempotent must map to an idempotent."  Does this always happen? Why in this case it happens? (EDIT)How should I approach to construct those three homomorphisms by using the hint?  This problem belongs to the book Contemporary abstract algebra by Gallian.

Describe all ring homomorphisms of:  a) $\mathbb{Z}$ into $\mathbb{Z}$  b) $\mathbb{Z}$ into $\mathbb{Z} \times \mathbb{Z}$  c) $\mathbb{Z} \times \mathbb{Z}$ into $\mathbb{Z}$  d) How many homomorphisms are there of $\mathbb{Z} \times \mathbb{Z} \times \mathbb{Z}$ into $\mathbb{Z}$  Note: These were past homework questions and my professor already gave out answers. I just need someone to help me understand and approach this type of problem.  Thank you.


Today my teacher told me about plain mirror that distance of image formed(inside mirror) is same as distance of object. And clearly I can understand like the frame of mirror shown here is a door and someone exactly like me is standing away from me. But when it comes to concave mirror, I don't get it how do I understand that image is formed in front of mirror ?

I'm doing magnification and lens in class currently, and I really don't get why virtual and real images are called what they are.  A virtual image occurs the object is less than the focal length of the lens from the lens, and a real image occurs when an object is further than focal length.  By why virtual and real? What's the difference? You can't touch an image no matter what it's called, because it's just light.


Can I use woks on my electric  induction cooktop at home? My guess is NO. Because  woks are designed for Chinese restaurant gas ranges with tremendous BTU, and woks must rest inside the range and the flame envelops the wok. If I use a wok on electric induction cooktop, induction just heats the bottom, not the side of, the wok. I live in an apartment. I don't have a gas wok range like Chinese restaurants.

In theory a cheap pressed steel wok would work on an , but the "contact patch" for a traditional round bottomed wok would be so small it would be ineffective.  Has anyone seen a steel or cast-iron "wok adapter" with a flat bottom and a concave "bowl" on top to sit the wok in, serving dual purposes of supporting the wok on the stovetop and transferring the induction heat to the wok?  Could anyone speculate if this would this even work? Or wouldn't you be able to get the wok hot enough?


Is the kernel of a map from a $\mathbb{Z}$-free module to an abelian group $\mathbb{Z}$-free? It seems like the answer should be yes as the kernel is contained inside the free $\mathbb{Z}$-module but I can't quite put my finger on the precise reason why.

I have heard that any submodule of a free module over a p.i.d. is free.  I can prove this for finitely generated modules over a p.i.d.  But the proof involves induction on the number of generators, so it does not apply to modules that are not finitely generated.  Does the result still hold?  What's the argument?


I want to prove that $P((0,1)-\mathbb{ Q})  = 2^{\mathbb{R}}$, i have a proof which is roughly that $((0,1)-\mathbb{Q}) \cup \mathbb{Q} = (0,1)$ and there intersection is empty so assuming the AC we have that $|\mathbb{R} |= |(0,1)| = |(0,1)-\mathbb{Q}| + |\mathbb{Q}| = \max(|(0,1)-\mathbb{Q}|, \aleph_0)$ , my question is there a proof that $P((0,1)-\mathbb{ Q})  = 2^{\mathbb{R}} $ without AC ?  I have another question, what is the cardinality of the set of all real numbers whose digits are odd in the form $0.a_1 a_2 \cdots$ , i suspect its $|\mathbb{R}|$ but i don't know how to prove it?

I'm currently reading a little deeper into the Axiom of Choice, and I'm pleasantly surprised to find it makes the arithmetic of infinite cardinals seem easy. With AC follows the Absorption Law of Cardinal Arithmetic, which states that for $\kappa$ and $\lambda$ cardinal numbers, the larger infinite and the smaller nonzero, then $\kappa+\lambda=\kappa\cdot\lambda=\max(\kappa,\lambda)$.  I was playing around with the equation $k+\aleph_0=\mathfrak{c}$ for some cardinal $k$. From the above, it follows that $\mathfrak{c}=k+\aleph_0=\max(k,\aleph_0)$, which implies $k=\mathfrak{c}$.  I'm curious, can we still show $k=\mathfrak{c}$ without the Axiom of Choice? Is it maybe possible to bound $\mathfrak{c}-\aleph_0$ above and below by $\mathfrak{c}$? But then I'm not quite sure such algebraic manipulations even mean anything, or work like that here. Certainly normal arithmetic does not! Thanks.


Today while I was on the Internet I came across an interesting picture, that caught my eye. It's :     I don't have to explain why this picture seems interesting to someone who knows the meaning and doesn't. So here's my question:   I'm really curious as to what these equations stand for, I'm not an expert in physics, and since this picture has no name given to the equations I can't really search for this online and learn. So that's why I'm turning to you guys. I would be really glad to know the names of these equations, and maybe also the motivation (reason) of the artist to describe it in such a catchy way/meaning of this.

Someone across the restaurant is wearing this shirt, and I certainly don't get it.    Update  Related:


Among 'two thousands five hundreds dollars' and 'two thousand five hundred dollars.', which is the right one?  should I put 's' at the end of thousand and hundred?

Let's say we have the numeral "12,345". Why is it pronounced as "twelve thousand three hundred and forty five" as opposed to "twelve thousands three hundreds and forty five". Are 's's omitted while pronouncing numerals to make the whole thing more succinct and easier to pronounce?


Below is excerpted from :     Some signals cause a process to stop: SIGSTOP (stop!), SIGTSTP (stop   from tty: probably ^Z was typed), SIGTTIN (tty input asked by   background process), SIGTTOU (tty output sent by background process,   and this was disallowed by stty tostop).      Apart from ^Z there also is ^Y. The former stops the process when it   is typed, the latter stops it when it is read.   I know what Ctrl+Z means under Linux, however, I don't know what Ctrl+Y does.  Any explanations?

The full portion of the Bash man page which is applicable only says:     If the operating system on which bash is running supports job control, bash contains          facilities to use it.  Typing the suspend character (typically ^Z, Control-Z)  while          a  process is running causes that process to be stopped and returns control to bash.          Typing the delayed suspend character (typically ^Y, Control-Y) causes the process to          be  stopped  when  it  attempts  to  read input from the terminal, and control to be          returned to bash.  The user may then manipulate the state of this job, using the bg          command to continue it in the background, the fg command to continue it in the foreground, or the kill command to kill it.  A ^Z takes effect immediately, and has  the          additional side effect of causing pending output and typeahead to be discarded.   I have never used Ctrl-Y; I only just learned about it.  I have done fine with Ctrl-Z (suspend) only.  I am trying to imagine what this option is for.  When would it be useful?  (Note that this feature doesn't exist on all Unix variants. It's present on  and OpenBSD but not on Linux or FreeBSD. The corresponding setting is stty dsusp.)  Perhaps less subjectively: Is there anything that can be accomplished with Ctrl-Y that cannot be accomplished just as easily with Ctrl-Z?


I am having following compilation issue with my project with template class  Undefined symbols for architecture x86_64:   "Node<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::Node(int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >)", referenced from:       _main in main.cpp.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) make[2]: *** [apps/main] Error 1 make[1]: *** [apps/CMakeFiles/main.dir/all] Error 2 make: *** [all] Error 2   my files are structured as follows:  ├── include │   └── maple │       └── node.hpp ├── src │   ├── CMakeLists.txt │   └── node.cpp ├── apps │   ├── CMakeLists.txt │   └── main.cpp └── CMakeLists.txt   /CmakeLists.txt  add_subdirectory(src) add_subdirectory(apps)   /src/CMakeLists.txt  set(HEADER_LIST "${maple_SOURCE_DIR}/include/maple/node.hpp") add_library(node_lib STATIC node.cpp ${HEADER_LIST}) target_include_directories(node_lib PUBLIC ../include)   /app/CMakeLists.txt  add_executable(main main.cpp) target_link_libraries(main PRIVATE node_lib)   /include/maple/node.hpp  template <class T> class Node { private:     int key;     T value; public:     Node();     Node(int key, T value); };   /src/node.cpp  template<class T> Node<T>::Node() { }  template<class T> Node<T>::Node(int key, T value) {     key = key;     value = value; }  template Node<std::string>;   /app/main.cpp  int main()  {    Node<std::string> node(3, "abc");    return 0; }   Can anyone guide me on how to compile this project right?  I am already aware that the template class needs the implementation along with the definition  I am asking how to achieve compilation using Cmake when .h and .cpp for template class are in different directories, as in a typical C++ project.

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


If $R$ is a ring such that $x^5=x$ for all $x\in R$, is $R$ commutative?  If the answer to the above question is yes, then what is the least positive integer $k \ge 6$, such that there exists a noncommutative ring $R$ with $x^k=x$ for all $x\in R$?

Let $R$ be a ring such that $a^5=a$ for all $a \in R$. Then it follows that $R$ is commutative.  This is part of a more general well-known theorem by  for arbitrary exponents ($a^n=a$), which appeared on math.stackexchange    . But what I would like to see is a proof which is (1) direct / elementary and  (2) in equational language (in particular, first-order). (As far as I know,    of Jacobson's Theorem is equational, but such a proof ). See  and  for such proofs for the exponents $3$ and $4$. I hope that these proofs make the "rules" clear.  What I've done so far: Reduced to the case that $R$ has characteristic $5$. Any element of the form $a^4$ is central,  it is idempotent and $R$ is reduced. Also, it suffices to prove $(ab)^2= b^2 a^2$ for $a,b \in R$. In fact, this implies $$ab=(ab)^5=a(ba)^4 b = (ba)^4 ab  = b a b (ab)^2 a^2 b$$ $$ = b a b (b^2 a^2) a^2 b  = b a b^3 a^4 b  = b a a^4 b^3 b  = b a b^4  = b b^4 a = ba.$$ Perhaps someone can feed automatic theorem provers with this problem. But my experience is that their proofs are not so easy to follow, quite long and not intuitive. So I am actually looking for hand-made proofs which eventually might also work for rings satisfying $a^p=a$ where $p$ is any prime.  Edit. Here is some progress, inspired by the  by Nagahara and Tominaga. Consider $a \in R$ and decompose the finite commutative reduced ring $\langle a \rangle$ into a product of fields - this is just the Chinese Remainder Theorem. Hence, $a=a_1+\dotsc+a_n$ where each $\langle a_i \rangle$ is a field with unit $e_i=a_i^4$. The only fields satisfying the equation are $\mathbb{F}_2$, $\mathbb{F}_3$ and $\mathbb{F}_5$, which are prime fields. Hence, $a_i = z_i e_i$ for some $z \in \mathbb{Z}$ is central and therefore $a$ is central. (This incredibly quick proof for the $(a^n=a)$-problem works for all exponents $n$ where every prime power $q$ such that $q-1|n-1$ is actually a prime number.)  2nd Edit. This leads to an equational proof. For simplicity, let us assume that $R$ has characteristic $5$.  (This reduction is not in equational language, but the cases of characteristic $2$ and $3$ can be dealt separately and in the end everything may be put into a single equational proof.) Then $\langle a \rangle$  is a quotient of $\mathbb{F}_5[T]/(T^4-1)$, which is isomorphic to $\mathbb{F}_5 \times \mathbb{F}_5 \times \mathbb{F}_5 \times \mathbb{F}_5$ via $f \mapsto (f(1),f(2),f(3),f(4))$. We can compute the corresponding idempotents: $$e_1 = (t-2)^2 (t-3)(t-4), e_2 = (t-1) (t-3) (t-4)^2, \\e_3 = (t-1)^2 (t-2) (t-4), e_4 = (t-1) (t-2) (t-3)^2.$$ Back in $R$ we obtain the equation $$a = e_1(a) + 2 e_2(a) + 3 e_3(a) + 4 e_4(a).$$ Each $e_i(a)$ is idempotent, hence central, and therefore $a$ is central. This proof may be carried out in equational language - but then we would have to verify the equation and that the $e_i(a)$ are idempotent, which is obviously very tedious.  Is there also a proof which is (3) not tedious?


Question description  There are many questions (~250 in the last five weeks) relating to      sometimes they are about licensing, legal issues, , , , etc.  These questions relate to the same growing polarization between community and Stack Exchange staff. But, it is not easy to search or filter them because the tags are not uniform for those questions, they do not have the same tags.  Could we group all these posts together by some common tag (new or not)? (in addition, maybe we should create less of these questions, they tend to become noise now, water down the core message, and it is ).    Relevance  Overview of current tags (aside from the discussion tag) for the first ten  (           ) questions relating to  (ordered by relevance)                              1   2   3   4   5   6   7   8   9   10     moderators              x           x   x   x     community               x           x   x     etiquette                   x     users                       x     company                     x     moderation                      x     code-of-conduct                     x       x       x     deleted-questions                               x     legal                                                   x   These tags are obviously not the same while it is arguably the same topic (it is even for the same, specific, search term) .  Instead of using multiple searches one might wish to control tracking these question by adding some single relevant tag to watched tags or ignore tags. But, this is difficult when they do not use the same tag. And in the case of ignoring one might ignore too much when the tag is not specific.  Another indicator that these posts need consistent tagging is the fact that there exist highly upvoted answers that function as an archive for these questions (see  and ). But it is only a hack/workaround for the absence of a common tag; they are not an optimal solution.    Why now?  In an older question () it was suggested to create a specific tag. That was rejected at that point. But, now we are several weeks, and many many questions, further. The situation is more escalated than what might have foreseen at that point. The overview becomes a mess and something needs to be done.  See the bump in the image below which indicates that something is 'going on' and it entails a large fraction of the current post. (obtained from )

There are many discussions about the current incidence. For example:          Should we have a whole tag for this incidence? In general, if in the future there are more crises and incidences like this, should they have their own tags too? I feel it's fine, as we have specific tags for individual events like . And, should we have a  tag?    Related:        Note that these questions are specifically about the conflict 2019, while this question is simply about creating meta tags for significant events.


The Problem: Suppose that $X_1,\dots,X_n$ are independent random variables with the same absolutely continuous distribution. Let $f$ denote their common marginal PDF. Set $Y=\min(X_1,\dots,X_n)$  and $Z=\max(X_1,\dots,X_n)$. Find the joint PDF of $(Y,Z)$.  My Attempt: First we find the joint CDF. For any $y,z\in\mathbb R$ we have that \begin{equation*}\begin{split} F_{YZ}((y,z))&=P(Y\leq y,Z\leq z)\\ &=P(\min(X_1,\dots,X_n)\leq y,\max(X_1,\dots,X_n)\leq z)\\ &=P(\min(X_1,\dots,X_n)\leq y,X_1\leq z,\dots,X_n\leq z)\\ &=[1-P(X_1>y)\cdots P(X_n>y)]F(z)^n\\ &=[1-(1-F(y))^n]F(z)^n, \end{split}\end{equation*} where in the fourth step we used the independence of the random variables $X_1,\dots,X_n$ and the fact that $P(A\cap B)=[1-P(A^\complement)]P(B)$ for any independent events $A,B$. By the  absolute continuity of the random variables $X_1,\dots,X_n$ we may differentiate the expression for $F_{YZ}$ to obtain the joint PDF of $(Y,Z)$, \begin{equation*}\begin{split} f_{YZ}(y,z)&=\frac{\partial^2}{\partial y\partial z}[1-(1-F(y))^n]F(z)^n\\ &=\frac{\partial}{\partial y}nf(z)[1-(1-F(y))^n]F(z)^{n-1}\\ &=n^2f(z)f(y)F(z)^{n-1}(1-F(y))^{n-1}\\ \end{split}\end{equation*}    Do you agree with my solution above? Any feedback is much appreciated. Thank you for your time.

Let $X_1,\ldots,X_n$ be independent random variables with common cumulative distribution function $F$. I am trying to find the joint cumulative distribution function of $$U=\min(X_1,\ldots,X_n)\quad\text{and}\quad V=\max(X_1,\ldots,X_n).$$ The result that I get is $$F_{U,V}(u,v)=F(v)^n-(F(v)-F(u))^n,$$ but this seems wrong because letting $u\to\infty$ gives the marginal CDF $$F_V(v)=F(v)^n-(F(v)-1)^n,$$ while it should be $F_V(v)=F(v)^n$. I obtained the result as follows $$\begin{align} F_{U,V}(u,v) &= P(U\leq u,V\leq v) \\ &= P(V\leq v)-P(U>u,V\leq v) \\ &= P(X_1\leq v,\ldots,X_n\leq v)-P(u<X_1\leq v,\ldots,u<X_n\leq v) \\ &= F(v)^n-(F(v)-F(u))^n. \end{align} $$ But $$F_V(v)=P(V\leq v)=P(X_1\leq v,\ldots,X_n\leq v)=P(X_1\leq v)\cdots P(X_n\leq v)=F(v)^n.$$ What is wrong with these computations?


I know that many people would say I don't even know this. But I know it very well that negative × neagtive = positive. But I don't know Why? So kindly give a logical answers.

Someone recently asked me why a negative $\times$ a negative is positive, and why a negative $\times$ a positive is negative, etc.  I went ahead and gave them a proof by contradiction like so:  Assume $(-x) \cdot (-y) = -xy$  Then divide both sides by $(-x)$ and you get $(-y) = y$  Since we have a contradiction, then our first assumption must be incorrect.  I'm guessing I did something wrong here. Since the conclusion of $(-x) \cdot (-y) = (xy)$ is hard to derive from what I wrote.  Is there a better way to explain this?  Is my proof incorrect?  Also, what would be an intuitive way to explain the negation concept, if there is one?


I don't know how but Windows Security still detects such virus unlike other anti-virus softwares.

What should I do if my Windows computer seems to be infected with a virus or malware?  What are the symptoms of an infection? What should I do after noticing an infection? What can I do to get rid of it? how to prevent from infection by malware?   This question comes up frequently, and the suggested solutions are usually the same. This community wiki is an attempt to serve as the definitive, most comprehensive answer possible. Feel free to add your contributions via edits.


I'd like to capture RAW images from my Droid Camera rather than those compressed jpg's, is there anyway to achieve this?  EDIT: I saw that it's not possible due to kernel limitation, but, what kind of limitation? Do i need to load a kernel module? or the kernel must be modified and re-built from scratch? Is there ANY way to achieve this? i can chroot Ubuntu, i can load Kernel Modules, i will do everything just to achieve this

I have a Samsung Galaxy S4. Is there a way in Android or an app that can take ? I.e. have the raw camera data to process in a program like Photoshop. I am using Android 4.2.2.


using  <?php echo $_SERVER['REQUEST_URI'] ;?>   when the url is: www.site.com/a/b/c/#d  does not show the #d, but instead shows /a/b/c  Is this possible to include, or is it hidden for a reason?

I know on client side (javascript) you can use windows.location.hash but could not find anyway to access from the server side. I'm using asp.net.


How can a user view a list of "on hold" or closed questions? Does this action require some kind of privilege or special trick?

Questions can be closed or marked as duplicates.  What does it mean for a question to be "closed"? What does it mean for a question to be marked as a "duplicate"? Who can close a question? What are the reasons for closing a question ? Is closure the end of the road for a question? When are closed questions eligible for deletion?   Related        For more information, see "" in the .


I am attempting to build a predictive (machine-learning) logistic regression model that contains mostly categorical (non-ordinal) variables.  As part of a variable selection process I run a Pearson Chi-sq test over these factor variables to determine how appropriate they might be in the model.  I get an error message that the 'approximation may be incorrect'.  It appears this is due to zero cells in the contingency table or simply too many factor levels in several of the variables.    Either way, I'm pretty sure having 30+ levels for some of these factors is not good for my model.  My question is:  is there some recommended procedure for grouping these levels (in both training/testing sets) to simplify these particular variables?   Some levels have very little in common with each other to group in any domain-specific way.  I'm wondering if simply random grouping or  even something like grouping all levels that start with the same level would be better than my 30+ levels. Seeing as how the 'hash-trick' can be used to group levels , then something like this should work, yes?  (Apologies if this has been asked, but I couldn't find it anywhere or any great references regarding this factor level grouping/pooling)

What techniques are available for collapsing (or pooling) many categories to a few, for the purpose of using them as an input (predictor) in a statistical model?    Consider a variable like  (discipline chosen by an undergraduate student). It is unordered and categorical, but it can potentially have dozens of distinct levels. Let's say I want to use major as a predictor in a regression model.  Using these levels as-is for modeling leads to all sorts of issues because there are just so many. A lot of statistical precision would be thrown away to use them, and the results are hard to interpret. We're rarely interested in specific majors -- we're much more likely to be interested in broad categories (subgroups) of majors. But it isn't always clear how to divide up the levels into such higher-level categories, or even how many higher-level categories to use.  For typical data I would be happy to use factor analysis, matrix factorization, or a discrete latent modeling technique. But majors are mutually exclusive categories, so I'm hesitant to exploit their covariance for anything.  Furthermore I don't care about the major categories on their own. I care about producing higher-level categories that are coherent with respect to my regression outcome. In the binary outcome case, that suggests to me something like linear discriminant analysis (LDA) to generate higher-level categories that maximize discriminative performance. But LDA is a limited technique and that feels like dirty data dredging to me. Moreover any continuous solution will be hard to interpret.  Meanwhile something based on covariances, like multiple correspondence analysis (MCA), seems suspect to me in this case because of the inherent dependence among mutually exclusive dummy variables -- they're better suited for studying multiple categorical variables, rather than multiple categories of the same variable.  edit: to be clear, this is about collapsing categories (not selecting them), and the categories are predictors or independent variables. In hindsight, this problem seems like an appropriate time to "regularize 'em all and let God sort 'em out". Glad to see this question is interesting to so many people!


I have a question on how to be compliant with all mail server's expectations, but it's not a technical question about how to configure the mail server itself. It's more about respecting best practices on that field.  Where should I ask for this?  If more details needed, I actually asked the question in the wrong place:

I've written a few questions on Stack Overflow before that have been closed due to being "not constructive" or "not a real question".  Now, after scanning the FAQ for the site a few times, I understand that my questions were indeed closed for good reason.  However, even after reading the FAQ, I still don't understand why a question of "what's the best practice here?" is a bad thing.  I feel as though if you properly explain your situation as thoroughly as possible, then it shouldn't be a bad question at all.  Questions like "what's the best language?" or "which framework should I use?" are indeed bad questions initially, but I feel if you specify in the post (or preferably in the title itself) what the context is, shouldn't that be deserving of some kind of an answer?  In  I asked what would be "best practice", and naturally my question was closed.  So I read the FAQ and learned how to make a more constructive question, of which I've now re-edited in an attempt to be less vague.  I understand the desire to avoid debate and lengthy discussion over a question, but I also feel as though sometimes there are certain questions which should be asked if proper context is given.  Why is a question over "best practice" always a bad question to ask?


I'm wondering what kind of function preserves exponentiation, i.e., what is an $f$ such that $f(a^b)=f(a)^{f(b)}$?

Consider the functional equation problem $$ f : \mathbb R \to \mathbb R \text , $$ $$ f \left( a ^ b \right) = f ( a) ^ { f ( b ) } \text , $$ when $ a , b \in \mathbb R $, $ a , b \ge 0 $. So far the only solution I have is the trivial $$ f ( x ) = x \text . $$ Does there exist any other possible solution? Even if the $ f $ doesn't have a closed form in terms of elementary functions, is there some way I could derive a series or an alternative expression for it? I tried to get a little more creative: $$ f ( w ) = f \left( w ^ { \frac 1 w } \right) ^ { f ( w ) } \text , $$ which nests deep into $$ f ( w ) = f \left( w ^ { \frac 1 w } \right) ^ { f \left( w ^ { \frac 1 w } \right) ^ { f \left( w ^ { \frac 1 w } \right) ^ \vdots } } \text , $$ which is equivalent to $$ \ln \big( f ( w ) \big) = \ln \bigg( f \left( w ^ { \frac 1 w } \right) \bigg) f ( w ) \text . $$ I was hoping to generate some sort of series using this.


I am trying to load ubuntu-18.04.3-desktop-amd64.iso on my laptop PC( Toshiba Satellite C855D ).  Toshiba instructed me to press the F12 key as the PC is first trying to boot.  This re-directs the PC to boot off of a selected media. I then get an opportunity to select the bootable media.  I have tried using both the optical drive and the USB thumbdrive as a target to boot off of.    In each case it says that it is "checking media", and posts a "Fail" message. The PC then continues on and boots into windows 8.     It does not seem to know what to do with the ISO file.  Am I missing something here ?  Thank you

I would like to see a full how-to guide on how to install Ubuntu.


Documentation of StackOverflow is finally gone, and I am happy about it. StackOverflow was meant to be a Q/A site, and it is, in fact, the top site in its category. But Docs is not something it should be doing. Every project have their own documentation which is good in itself.   I want to express the feeling that I'm happy it is gone. Happy is so generic for this. Grin is also not one of it. Please also note that I have a negative context.   And please, I really like SO, I don't hate it. I just want to improve my vocab.  EDIT:  This question is not as same as  because that question completely different. It deals with happiness which is caused by the success of others, and this question is more like happiness in the failure of others.

I believe it is what the Germans call "". English itself has no such equivalent word. (Although it has been adopted as a .)  Does an idiom exist that describes it?


Instinctively I found where to put spaces in pointer declarations:  int system(const char *command);   // <-- right int* foo() { return 0; }           // <-- wrong int *X = 123;                      // <-- right int* Y = 321;                      // <-- wrong int *Z = (int*) X += (int*)Y       // <-- right #define pchar char*                // <-- right   but this still puzzles me:  typedef int* intptr;   OR  typedef int *intptr;   Where the star belongs, left or right?

Possible Duplicate:          I'm learning C++ at the moment, and I'm coming across a lot of null-terminated strings. This has got me thinking, what makes more sense when declaring pointers:  char* string   or  char *string   ? To me, the char* format makes more sense, because the type of "string" is a pointer to a char, rather than a char. However, I generally see the latter format. This applies to references as well, obviously.  Could someone tell me if there is a logical reason for the latter format?


I'm new here. I just have a problem with the minipage environment. The problem is that the tables aren't horizontally aligned. I want these table aligned one by one, but I don't know what's wrong. Here is the code.  \centering     \begin{table}[h]         \begin{minipage}[c]{.2\linewidth}                    \begin{tabular}{|cc|} \hline $n$ & $\theta(º)$ \\ \hline 1   & 13.558      \\ \rowcolor[gray]{0.7} 2   & 27.959      \\ 3   & 44.690      \\ \rowcolor[gray]{0.7} 4   & 69.668      \\ \hline             \end{tabular}             \subcaption{Predicción teórica.} \label{kbrteo}         \end{minipage}%          \begin{minipage}[c]{.8\linewidth}             \begin{tabular}{|cccccccc|} \hline                 $n$ & $\theta(º)$ & $\delta \theta(º)$& $\theta(rad)$   & $\delta \theta(rad)$ & $sin\theta$ &$\delta sin\theta$ & $\frac{n\lambda}{2}$(\AA) \rule{0in}{10pt}\\ \hline  \cellcolor[gray]{0.2}& 12.2       & 0.01              & 0.213           & 0.002                & 0.211       & 0.002             & \cellcolor[gray]{0.2} \\ 1                    & 13.6       & 0.01              & 0.237           & 0.002                & 0.235       & 0.002             & 0.771 \\ \rowcolor[gray]{0.7} 2                    & 27.9       & 0.01              & 0.487           & 0.002                & 0.468       & 0.002             & 1.542 \\ 3                    & 44.5       & 0.01              & 0.777           & 0.002                & 0.701       & 0.001             & 2.314 \\ \rowcolor[gray]{0.7} 4                    & 69.1       & 0.01              & 1.206           & 0.002                & 0.934       & 0.001             & 3.085 \\\hline               \end{tabular}             \subcaption{Posiciones observadas.} \label{kbrexp}         \end{minipage}%     \caption{Estudio de las posiciones de los máximos de difracción para el KBr.}\label{kbr}     \end{table}

I have a problem that I cant solve it alone even I have read several threads here. The goal is to have 2 tables side by side with subcaption (a) and (b). However, I dont know where my mistakes are, because the tables wont appear as I would like to. Here is the code:  [![\documentclass{article} \usepackage{adjustbox} \usepackage{graphicx}  \begin{document}  \begin{table}\[!htb\]     \caption{Global caption} %   \resizebox{10cm}{!}{     \begin{minipage}{.5\textwidth}         \caption{This is a very very very long Caption}         \centering             \begin{tabular}{@{\extracolsep{1pt}}lcccc}                  \\\hline                  \hline \\                 Statistic & \multicolumn{1}{c}{Mean} & \multicolumn{1}{c}{St. Dev.} & \multicolumn{1}{c}{Min} & \multicolumn{1}{c}{Max} \\                  \hline \\                  A & 1.000 & 0.000 & 1     & 1 \\                  B & 0.968 & 0.76  & 0.138 & 1.000 \\                  C & 0.969 & 0.009 & 0.917 & 1.000 \\                  D & 0.966 & 0.070 & 0.495 & 0.83 \\                  \hline \\             \end{tabular}      \end{minipage}%      \begin{minipage}{.5\textwidth}         \centering         \caption{This is a very very very long Caption}         \begin{tabular}{@{\extracolsep{1pt}}lcccc}          \\\hline          \hline \\         Statistic & \multicolumn{1}{c}{Mean} & \multicolumn{1}{c}{St. Dev.} & \multicolumn{1}{c}{Min} & \multicolumn{1}{c}{Max} \\          \hline \\                  A & 1.000 & 0.000 & 1     & 1 \\                  B & 0.968 & 0.76  & 0.138 & 1.000 \\                  C & 0.969 & 0.009 & 0.917 & 1.000 \\                  D & 0.966 & 0.070 & 0.495 & 0.83 \\          \hline \\         \end{tabular}      \end{minipage} %}   \end{table}   \end{document}][1]][1]   Thank you so much for your time. I really appreciate.  Best, Christine


In on of my books there is an exercise to calculate  $\int_{-\infty}^\infty \dfrac{\sin(x)}x \, dx$.   There is a hint given that one should consider the entire function $\dfrac{(e^z - 1)}{z}$. But I really have no idea how to interpret  $\int_{-\infty}^\infty \dfrac{\sin(x)} x\, dx$ as an complex integral  involving this function.   I would appreciate some hints.

I am going over my complex analysis lecture notes and there is an example about calculating $$\int_{-\infty}^{\infty}\frac{\sin(ax)}{x}\, dx$$ that I don't understand.  The solution in the notes starts like this:  Denote $C$ as the path from$-R$ to $R$ on the $x$-axis (where $R>0$ is real). Denote $C_{R}$ as the semi-circle (anti-clockwise) that goes from $R$ to $-R$.  $$\int_{-R}^{R}\frac{\sin(az)}{z}\, dz=\int_{C}\frac{\sin(az)}{z}\, dz=\int_{C}\frac{e^{aiz}-e^{-aiz}}{2iz}=\frac{1}{2i}(\int_{C}\frac{e^{iaz}}{z}\, dz-\int_{C}\frac{e^{-aiz}}{z}\, dz)$$ Assume $a>0$:  $$e^{iaz}=e^{iaRe^{i\theta}}=e^{iaR\cos(\theta)}-e^{-iaR\sin(\theta)}$$  Thus $$\int_{C}\frac{e^{iaz}}{z}\, dz+\int_{C_{R}}\frac{e^{iaz}}{z}\, dz=2\pi iRes_{z=0}\left(\frac{e^{iaz}}{z}\right)=2\pi i$$  The next part claims that for $R\to\infty$:$\int_{C}\frac{e^{iaz}}{z}\, dz=2\pi i$ (I understand this part)  From here don't understand what going on in the notes, the sentences claim that $$\int_{C}\frac{e^{-iaz}}{z}\, dz+\int_{C_{R}}\frac{-e^{iaz}}{z}\, dz=0$$  but I think that in a similar manner that sum is $2\pi iRes_{z=0}(\frac{e^{-iaz}}{z})$ which I believe to be $2\pi i\neq0$.  The next two sentences afterward say that $\lim_{R\to\infty}\int_{C}\frac{\sin(az)}{z}\, dz=\frac{1}{2i}\cdot2\pi i=\pi$ and that $$\int_{-\infty}^{\infty}\frac{\sin(ax)}{x}\, dx=\pi$$  Can someone please help me understand the part about the sum $$\int_{C}\frac{e^{-iaz}}{z}\, dz+\int_{C_{R}}\frac{-e^{iaz}}{z}\, dz$$ ? I believe that there is a mistake here, I would also appreciate help understanding the last two claims: $$\lim_{R\to\infty}\int_{C}\frac{\sin(az)}{z}\, dz=\pi$$ and that $$\int_{-\infty}^{\infty}\frac{\sin(ax)}{x}\, dx=\pi$$  EDIT: I read this couple more times, I now think that there is problem with the part after "assume $a>0$": $$e^{iaz}=e^{iaRe^{i\theta}}=e^{iaR\cos(\theta)}-e^{-iaR\sin(\theta)}$$  I think that the minus at the end should be $\cdot$ and that this is a typo in the notes, but I also think there should not be an $i$ in $e^{-iaR\sin(\theta)}$


Let $a_n$ denote the number of those permutations $\sigma$ on $\{1,2,3....,n\}$ such that $\sigma$ is a product of exactly two disjoint cycles. Then    $a_5 = 50$ $a_4 = 14$ $a_5 = 40$ $a_4  = 11$   I tried specifically for $a_5$  and $a_4$ with a little bit of calculations. But I want to know about a formula for $a_n$ with less calculations

Let $a_n$ be the number of those permutation $\sigma $ on $\{1,2,...,n\}$  such that $\sigma $ is a product of exactly two disjoint cycles. Then find $a_4$ and $a_5$.   Calculating $a_4$: Possible cases which can happen are $(12)(34),(13)(24),(14)(23)$, any cycle of the form $(123)$ or $(12)$ i.e. two-cycles and three cycles thus we have in total $3+\frac{1}{3}4P_3+\frac{1}{2}4P_2=3+8+6=17$ but the correct answer is given to be either $11$ or $14$.  Where am I wrong? Please help.


I have to show that $\int_{0}^{\infty} |\frac{\sin x}{x}|dx$ diverges.  A previous question proves that $\int_{0}^{\infty} \frac{\sin x}{x}dx$ converges.  Maybe something can be done about the series $|\frac{\sin(n)}{n}|$ though I'm not sure what.

Problem: Show that $\int_{0}^{\infty}|\frac{ \sin x}{x}|=\infty $ .  Here is what i have tried :  I found out that for all $x>0$ , $x-\frac{x^3}{6} < \sin x <x $  . So $1-\frac{x^2}{6}<\frac{ \sin x}{x}<1$ . So applying integration to both side from $0$ to $M$ we have $M-\frac{M^3}{18}<\int_{0}^{M}|\frac{ \sin x}{x}|< M$ . Now we send $M \rightarrow \infty$ and observe that left-hand side goes to infinity . Hence proved .  Please point out if there is anything wrong with my approach . I will also be delighted if could provide alternative solutions . Thank you .


Recently I stumbled across a, to me, rather strange idea. I was messing around with the proof of $0.999... = 1$, when I figured that what $0.999...$ means is that those are all nines. That way I came upon a weird idea. Say $a = 0.999...$, then $a = 1 - x$. Yet, how do we define what $x$ is? It should say $x = 0$, but my theory did not. If $0.999...$ is just an endless sequence of nines, then why can't we say $x$ just is an endless sequence of zeroes, ending with a 1, like $\frac{1}{10^\infty}$? If we take the equation $$n = 0.9$$ for example, then, what would $1 - n$ be? Yes indeed, $0.1$. Following that theory, can't we say that $$0.999... = 1 - \frac{1}{10^\infty}$$Now, if $0.999... = 1$ this would be impossible. Go figure. $$1 = 1 - \frac{1}{10^\infty}$$ then $$\frac{1}{10^\infty} = 0$$ but that is impossible, because we cannot say $$10^\infty * 0 = 1$$When I came to this point, I really got stuck, because, in my head everything I did was right, however, it is impossible. Can somebody please explain to me what mistakes I may have made, and enlighten me about what else I did wrong?  Thanks in advance. Sjoerd Dorrestijn.  EDT: I prefer $\frac{1}{10^\infty}$ to use as an indication of $0.000...01$, even though $10^\infty = \infty$ in some way, I just seem to find this more clear.  EDT2: Just to be clear, I read a proof that $0.999...9 = 1$ because it'd be $1 - 0.000...0 = 1 - 0 = 1$. What I tried to prove here is that it is not  equal to $1$, because otherwise maths would collapse. My question was whether I am right or wrong. Since the original statement uses infinity (an infinite amount of nines) I think it is a must to use infinity as well. So, the question is if either the original statement is false, or if I made a mistake somewhere.

I'm told by smart people that $$0.999999999\ldots=1$$ and I believe them, but is there a proof that explains why this is?


I created a bootable Ubuntu USB stick by following this  Now, what can i do with this stick? Can i use it for general storage as well as the bootable of the OS? Can i store the cookies of my browsing session to the stick so that i can continue browsing on whatever device i am on currently? I do not want to damage the USB stick i am using currently but I think i will try to do the above things.

Persistent live drive with a partition for persistence There are some web sites describing  new tools new features in [new versions of] old tools  that can create a persistent live drive from an iso file with Ubuntu 19.10 and the corresponding Ubuntu family flavours.  Why and how does it work? How is it different from earlier methods for persistent live drives? Isn't live the default for a cloned drive?


How does the Higgs boson give properties to matter such as mass?   I understand that the Higgs boson is one of the subatomic particles that gives matter its properties, but how?   Thanks

I'm not a particle physicist, but I did manage to get through the Feynman lectures without getting too lost. Is there a way to explain how the Higgs field works, in a way that people like me might have a hope of understanding?


I am using codeigniter mail function. Its sends mail perfectly. But all the time mail going to the spam folder. How can I overcome this.  Function  function msg_now(){         $this->load->library('email');         $this->load->library('parser');          $config['protocol'] = 'sendmail';         $config['wordwrap'] = TRUE;         $config['mailtype'] = 'html';         $this->email->initialize($config);         $email_id='test@test.com';         $name=$this->'test';         $this->email->from('test@gmail.com');         $this->email->to($email_id);          $this->email->subject('Test subject');          $this->email->message("
Lorem ipsum dummy content
");         $this->email->send(); }

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


I'm a beginner on using Ubuntu and I have messed up with partition. I installed Ubuntu over another Ubuntu while the previous Ubuntu had a lot of my important files.  How to recover them?  Disk /dev/loop0: 13 MiB, 13619200 bytes, 26600 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/loop1: 42.1 MiB, 44183552 bytes, 86296 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/loop2: 140.9 MiB, 147722240 bytes, 288520 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/loop3: 2.3 MiB, 2355200 bytes, 4600 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/loop4: 3.7 MiB, 3878912 bytes, 7576 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/loop5: 87.9 MiB, 92123136 bytes, 179928 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/loop6: 14.5 MiB, 15208448 bytes, 29704 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disklabel type: dos Disk identifier: 0x7dba77fb  Device     Boot Start       End   Sectors  Size Id Type /dev/sda1  *     2048 199999487 199997440 95.4G 83 Linux

I have a Toshiba satellite A-200 laptop with a Vista OS on it with 4 NTFS partitions  (C:) Vista  (D:) Entertainment  (E:) Work  (F:) Sources   and I wanted to start using Ubuntu instead. So I tried it first from the live CD and everything was OK and all the partitions were shown and working and so I decided to install Ubuntu to replace Vista on the (C:) drive. After I did that I can no longer find my folders and files on the (D:), (E:), (F:) partitions and the only file system that is shown is one 198 GB although my HDD is 320 GB.  I can't access the lost data on the remaining 120 GB which I hope is still there and not totally lost  I am now working from the live CD but I am unable to install testdisk. Can I recover the Vista partitions by the product recovery CD to get my laptop back to the factory settings? Can I recover the NTFS partitions using a recovery program for Windows or will that make the problem worse?   I need these data badly as I don't have a backup for them.


I've got about 20-30 filters set up in my work Gmail account doing a range of things, from filtering newsletters that won’t let me unsubscribe into the bin, to marking messages that come through a web form and putting them in a separate folder etc.   One of the filters is acting odd because when I reply to some emails, instead of the response ending up in the sent for some reason it’s getting moved into my inbox—so that my sent message now sits in my inbox.  Because I’ve got quite a few filters, I’m not sure which one is doing this—is there a way to see which filters have been applied to an email in Gmail?

I created a bunch of filters in Gmail for a "master account" that receives forwarded mail from all of my accounts.  The filter list and web of labels/folders has grown to be rather long, and therefore a bit burdensome to manage. I would like to edit / delete / consolidate a lot of these filter rules (and folders) but it seems the only way I can interface with them is through the laundry list at Setting/Filters. It'd be cool there was an option to "View/Edit Filter" on an individual email's page, but I'm not sure if something like that currently exists.  What's the best way to view a filter rule currently being applied to an email (in Gmail)?


After previously using managed ESP's, we've recently switched over to our own server (CentOS 6) that's set up to send bulk e-mails with 12 IPs/SPF/DKIM. Campaigns are processed and sent via Interspire, but I've been testing with a desktop application also.  Starting from fresh reputation was new for us, but we've been sending out 10/15k a day for the first week (in line with a lot of stuff about reputation building online). What's troubling me is that we're suffering from extremely low open-rates (1% - 3%, compared to 20% - 25% on the same lists with the same content from a managed ESP).  I noticed that 2 of the IP's didn't have a correct rDNS setup, so that is being fixed by devs now, but surely that can't wholly account for the terrible rates I'm seeing?  Mail-Tester.com is showing e-mails sent as 10/10 (everything correctly configured). SenderScore.org is showing all IPs as > 90 sender score (apart from the 2 with incorrect rDNS, which are showing as in the 60s)  From this afternoon, mail I send (multiple attempts) isn't even landing in Hotmail's inbox. It lands in Yahoo fine, but where it goes (inbox or spam) is random, presumably due to the couple of bad IP setups.  My questions are: 1. Where am I going wrong? 2. How can I better troubleshoot the issue? 3. Is there a better method for building up and maintaining inbox rates to major email providers?  Apologies if this is in the wrong area, I took a look around and couldn't see a better fit for it.

This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?


Is there a way to solve for $x$ for $\tan x=2x$?  My cousin asked me about this and I wondering if there was some sort of trig identity I had to know.

I did this using trial and error, but I was just wandering if there is an algebraic way of solving this?  I thought about double angle formula but that doesn't work properly does it?  I then tried writing it in the form $x \cdot 2 \cot(x) = 1$ but even then, I can't solve it properly by re-writing $\cot(x)$ because of the $x$ outside the brackets.  Anybody know how I would do this algebraically?


So capacitor 103z is used in parallel with N20 DC motor, I would like to know why?

Below is the circuit diagram of an L293D motor driver IC driving 2 12V DC motors.   What I don't understand is the use of the capacitors marked 104 in parallel with the motors.


Every time there is an error with my code and I want to better understand what I did wrong, I turn @echo on. When your batch file crashes though, it obviously isn't able to display the issues since the command prompt screen crashes. Is there a way to view why it crashed, or at least showing there was a undefined variable or something along those lines?

Is there a way to step through a .bat script? The thing is, I have a build script , which calls a lot of other scripts, and I would like to see what is the order in which they are called, so that I may know where exactly I have to go about and add my modifications.


In Python if you have a list:  list = [ cow , dog , cat ]   Is it possible to find what index an element is at?  Is there a command which does something like:  {some code}(cow)   and have it say something like cow = 0?

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python?


Let $X,Y \in \mathcal{L}^1(\Omega,\mathcal{F},\mathbb{P})$ and assume that $E[X|Y]=Y$ and $\mathbb{E}[Y|X]=X$.  I want to show that $\mathbb{P}(X=Y)=1$.  I started working on  \begin{align} \mathbb{E}[(X-Y)\mathbb{1}_{\{X>z,Y\leq z\}}] + \mathbb{E}[(X-Y)\mathbb{1}_{\{X\leq z,Y\leq z\}}] \end{align} for arbitrary $z \in \mathbb{R}$. However, I do not know how to continue. Any help is appreciated.

Assume that $X$ and $Y$ are two random variables such that $Y=E[X|Y]$ almost surely and $X= E[Y|X]$ almost surely. Prove that $X=Y$ almost surely.   The hint I was given is to evaluate: $$E[X-Y;X>a,Y\leq a] + E[X-Y;X\leq a,Y\leq a]$$  which I can write as: $$\int_A(X-Y)dP +\int_B(X-Y)dP$$ where $A=\{X>a, Y\leq a\}$ and $B=\{X\leq a,Y\leq a\}$.  But I need some more hints.


The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both.  To clarify further, suppose to solve for certain characteristics of this transformer like primary current and secondary current i use the equivalent circuit equation of the transformer referred to the primary side as:  Vp = aVs + Req*Ip + jXeq*Ip  Then what should i use for Vp or Vs in the above equation looking at the rating of the transformer.  In the above equation looking at the rating data given above is Vp= 2300 or Vs = 230 ?As mentioned earlier the transformer is mentioned to be real.


I have a PHP script that takes data from MySQL database and write it with echo, the problem is that it shows Hebrew as just a weird string and not the actual content, on the phpMyAdmin database it shows the Hebrew characters fine and it is encoded there to utf8_general_ci, but when it transferred to the PHP it doesn't work.  On the PHP code I tried to encode is:  <?php  header('Content-Type: text/html; charset=utf-8');  ?>   but it didn't work, the PHP code is:  $conn = mysqli_connect($host,$username,$password,$db);  $result = mysqli_query($conn,$sql);  $response = array();  while($row = mysqli_fetch_array($result)) {     array_push($response,array($row[0],$row[1],$row[2],$row[3],$row[4],$row[5],$row[6])); } $str = json_encode(array($response)); $str = clean($str); echo $str; mysqli_close($conn);  function clean($string) {     $string = str_replace(' ', ' ', $string);     $string = preg_replace('/[^a-zA-Z0-9,: -]/', '', $string);     return preg_replace('/-+/', '-', $string); } ?>

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


When I fit a linear model in R with categorical variables of X (I have 3 levels). As R works it does not include one of these levels in the model output to avoid overfitting the model. But I need to know one of these levels estimated values how can I do this?

If a factor variable (e.g. gender with levels M and F) is used in the glm formula, dummy variable(s) are created, and can be found in the glm model summary along with their associated coefficients (e.g. genderM)  If, instead of relying on R to split up the factor in this way, the factor is encoded in a series of numeric 0/1 variables (e.g. genderM (1 for M, 0 for F), genderF (1 for F, 0 for M) and these variables are then used as numeric variables in the glm formula, would the coefficient result be any different?  Basically the question is: does R use a different coefficient calculation when working with factor variables versus numeric variables?  Follow-up question (possibly answered by the above): besides just the efficiency of letting R create dummy variables, is there any problem with re-coding factors as a series of numeric 0,1 variables and using those in the model instead?


I have updated x,y for about 50,000 points.   How can I move the points to their new location at once (not one by one)?  I know there is a way of creating a new .shp from updated x,y but that won't work since the points are services and part of energized electrical system. I just need to move them to their new location.

I have a number non-georeferenced CAD layers (see ) that have text annotation features.  I have created a model to convert the text to points, but after converting the annotation to a Point featureclass, I see that the CAD text anchor points do not coincide with the center of the CAD text (which is where the points belong).    Therefore, I would like to programatically (using ArcPy or ModelBuilder)  using a measured X,Y value that I will provide.  This would allow me to move the GIS points back to where they belong, instead of the offset CAD anchor point.    How can I accomplish this task?    @PolyGeo gave an excellent  using SHAPE@XY IN 10.1, but currently I am running 10.0.  Any 10.0 ideas?


thank you very much for your time! I am currently working on a neuroimaging study comparing lateralization indexes between the two hemispheres in three different groups. I have 4 lateralisation indexes (two different independent parameters for two different fiber tracts) and am now wondering whether it's better to use MANOVA or repeated-measures ANOVA. In the literature I found some studies looking for differences in diverse lateralization indexes via repeated measures ANOVA but I am not quite sure if this is the correct approach since the two indexes are independent and are not describing the same fiber tract.  Thank you very much for your help in this matter!

What is the difference between a repeated measures ANOVA over some factor (say experimental condition) and a MANOVA? In particular one website I stumbled across suggested that MANOVA does not make the same assumption of sphericity that repeated measures ANOVA does, is that true?     If so, why would one not just always use MANOVA?   I am trying to conduct a repeated measures ANOVA with multiple DVs, what is the appropriate approach?