You will take in a 5 digit lottery number and compare it to a winning lottery number.   If the input lottery number has a certain numbers correct you will tell the user how much they have won.   You should follow these steps:  1.Declare 2 5 element integer arrays. (a) One should be for the winning lottery number (hard code this as 12, 35, 34, 2, 5). (b) The other should be for the user’s lottery number input.  2.Declare an integer to count the number of matching lottery numbers.  2.Declare an integer to count the number of matching lottery numbers.  3.Prompt the user to enter their 5 digit lottery number using a for loop and put their numbers in the user’s lottery number array.  4.Compare the elements of the two arrays using a for loop and increment the counter variable declared above when there is a match.  Using the value held in the counter variable, display how much the user has won.  (a) 0 matching numbers: $0  (b) 1 matching number: $1  (c) 2 matching numbers: $50  (d) 3 matching numbers: $1,000  (e) 4 matching numbers: $50,000  (f) 5 matching numbers: $90,000,000  I have the code below so far:  public static void main(String[]args){      final int [] HardCoded = {12, 35, 34, 2, 5};     int UserInput [] = new int[5];      Scanner input = new Scanner(System.in);      System.out.println("Please enter 5 Numbers. ");      System.out.print("Numbers [0]: ");     UserInput [0] = input.nextInt();      System.out.print("Numbers [1]: ");     UserInput [1] = input.nextInt();      System.out.print("Numbers [2]: ");     UserInput [2] = input.nextInt();      System.out.print("Numbers [3]: ");     UserInput [3] = input.nextInt();      System.out.print("Numbers [4]: ");     UserInput [4] = input.nextInt();      System.out.println("Lottery Numbers are: " + HardCoded);      }  }   However, the issue is that the hardcoded value will not print and int UserInput [] = new int[5]; has to be 4 but i get an error so i have to put in 5?

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


I have used wijesekara layout with windows xp. at there i could use alt+num to type the keys that are not in the keyboard. but now in ubuntu wijesekara layout it seems that this doesn't work. how can i type speciall characters those have to be written in normally by pressing alt and entering a number?

The title pretty much says it all: how can I type Unicode characters - specifically the em-dash —?


I have the following bash script (test_script.sh): #!/bin/sh case=test  var1=90 echo "var1 = $var1"  var2=$(( var1 * 4 )) echo "var2 = $var2"  if (( var1 > 80 )) then         pot=filled else         pot=empty fi      cat > message.txt << EOF    Hellow world! The pot is $pot . EOF  The output of this script is: var1 = 90 var2 = 360 ./test_script.sh: 10: ./test_script.sh: var1: not found  What is the cause for this "var1: not found" message ? Thanks.

I have the following shell script that sums up all the arguments passed to it (space separated):  sum=0 for arg in "$@"; do     (( sum += arg )) done echo $sum   I have saved it as SumAll.sh. So, its supposed to function as follows:  sh SumAll.sh 2 4 6 8 20   or  bash SumAll.sh 1 -2 3 -3 -1   Both work on my local machine (MacBook), but when I try the same in a linux server, running the script with bash works, but with sh does not work. I get the following error:  sum: '+=': No such file or directory sum: arg: No such file or directory   Why is that? And how do I fix it?


EDIT: Basically, I want to see if one can construct examples of fields $F,K$ such that they don't have a common extension field.  Apologies in advance if this is obvious, but for example, is there a field containing isomorphic copies of both $\mathbb{C}$ and $\mathbb{Q}_p$ for any prime $p$? If not, what's a good field invariant that could tackle a lot of these kinds of questions? I was thinking of using Galois groups somehow, but not sure where to begin.  This comes from the observation that the underlying set of the geometric realisation (as a locally ringed space) $|F|$ of a functor $F: \textbf{CRing} \to \textbf{Set}$ can be given by $\text{colim}_\textbf{Fld} F(k)$ (limit taken over the functor sending a field $k$ to $F(k)$ and sending $f: k \to K$ to $F(f): F(k) \to F(K)$), where $\textbf{Fld}$ is the full subcategory of $\textbf{CRing}$ where the objects are fields.  If you want to see what this actually looks like, you can consider $\bigsqcup_{\textbf{Fld}} F(k)/\sim$, where $\sim$ is the equivalence relation generated by the relation $x \sim y$ for $x \in F(k)$ and $y \in F(K)$ if there exists $L$ and $f: k \to L$ and $g: K \to L$ such that $F(f)(x) = F(g)(y)$. Now, if such an $L$ existed always, then this would be an equivalence relation, but if not, then you have to basically force transitivity. So I'm wondering to what extent you really are doing this.

Let $K$ be a field having two field extensions $L\supseteq K$ and $M\supseteq K$. Does there exist a field $N$ along with embeddings $L\to N$ and $M\to N$, such that the diagram $$     \require{AMScd} \begin{CD}     K @>>> L\\     @V  V V @VV  V\\     M @>>> N     \end{CD} $$ is commutative? To put it less formally, do $L$ and $M$ have a common field extension $N$ (with $K$ lying in the intersection)?  If yes, consider this side question (but do leave an answer even if you can only answer the main question!): Does the above property of fields generalise to the following, stronger property? Let $p$ be either $0$ or a prime number. Does there exist a sequence of fields $$ \mathbb F_p = L_0\subseteq L_1\subseteq L_2\subseteq L_3\subseteq L_4\subseteq\cdots$$ (where I use the convention $\mathbb F_0 = \mathbb Q$) such that any field $K$ of characteristic $p$ has an extension field among the $L_\alpha$? This sequence should be understood as enumerated by ordinal numbers. In other words, what I need is a function that assigns to each ordinal number $\alpha$ a field $L_\alpha$ containing all $L_\beta$ with $\beta < \alpha$. (Intuitively, I suspect that this might depend on the Axiom of Choice.)  If the second property holds, it shows that you can essentially only extend a field in one "direction." It also shows that the class (it is obviously not a set) $\mathbb M_p = \bigcup_\alpha L_\alpha$ is a field (class). We can define all the usual field operations (addition, multiplication, division) here since all pairs of elements lie in $L_\alpha$ for a sufficiently large $\alpha$. This "monster field" of characteristic $p$ then contains all other set fields of that characteristic.


Let $S$ and $T$ be linear map defined on hilbert space $H$ s.t. $\langle Su,v \rangle=\langle u,Tv\rangle $ $\forall u,v \in H$. Then show that both $S$ and $T$ are bounded.  $\textbf{TRY-}$ If I can show $S$ is bounded than $T$ is bounded but I am unable to show $S$ is bounded. I was working on it but getting nowhere. Any help is appreciated. Thanks!

This is a question I'm struggling with for a while:  Let $H$ be a Hilber space. Let  $T,S: H\rightarrow H$ be linear operators (not neccessarily bounded) such that for every $x,y\in H$: $\langle Tx,y\rangle=\langle x,Sy \rangle$.  Prove $T,S$ are bounded.    What I did so far:  First attempt:  $||Tx||^2=\langle Tx,Tx\rangle=\langle x,STx\rangle\le||x||*||STx||\le||x||*||S||*||Tx||$  I'm not entirly sure I'm allowed to do the last inequallity, since $||S||$ might be $\infty$.  It follows $||Tx||\le ||x||*||S||$  and analogly  $||Sx||\le ||x||*||T||$  From the first I'd get $||T||\le ||S||$ and from the second $||S||\le||T||$. Therefore $||S||=||T||$. I don't know where to go from here.  Second Attempt: assume  $T$ isn't bounded, therefore so is $S$, therefore there are series $(x_n),(y_n)\subset H$ such that $||x_n||=||y_n||=1$ and $\lim ||Tx_n||=\infty,\lim ||Sy_n||=\infty$. I'll keep it going soon, but it didn't go so well..    I'd love some guide. Not neccessarily the whole solution, but something that would tell me what i'm missing.  Thanks :)


Evaluate the integral $$\int_0^1\frac{x^7-1}{\log (x)}\,dx $$   [1]:   I'm trying to solve this definite integral since 2 hours.  Please, I need help on this.

/A problem from the 2012 MIT Integration Bee is $$ \int_0^1\frac{x^7-1}{\log(x)}\mathrm dx $$ The answer is $\log(8)$. Wolfram Alpha gives an indefinite form in terms of the logarithmic integral function, but times out doing the computation. Is there a way to do it by hand?


I posted this question as a non-English mother tongue. I've seen a conversation as below (comments on ):  A: 8:56 Looks like it's not a game! B: yeah, it does.  So, did B agree to A or not? I am a bit confused with two interpretations.  Yeah, it looks like it's not a game Yeah, it looks like it's a game  I learned to say 'yes' or 'does' for a positive response and 'no' or 'doesn't' for a negative response. So, if B said 'does' to 'looks', the answer is (1.), but if he said 'does' against 'it is not', then the answer is (2.) One thing is that, 'does' cannot come after be verb, so I think (1.) is more probable. However, since I am not the native, I want to hear the answer from the native or an English expert.

I faced a problem to answer a negative question, for example, when someone asks you:      Don't you have any money?   It's a yes/no question but how should one answer the question without ambiguity?  When you answer "yes", does it mean "yes, I don't have any money"? or the other way "Yes, I do have money"? the questioner may think you are agreeing to the negative, that yes, you do not have any money.  I know it's better to answer with "on the contrary" but is it possible to answer yes or no?


I have in my bike a 1.9" tyre in the front wheel and a 2.2" in the rear. Is it safe to use this tyre sizes?

My used bike came with different front and rear tires. It appears to have some kind of Kenda commuter tire in the front, and Continental Country Ride in the rear. They are both the same size (700x28).  Is this perfectly acceptable or should a bike always have matching models (and/or size)?  My main concerns from mismatching tires:   Grip thresholds may be inconsistent Ride comfort?  Wear rates (but rears seem to wear faster anyway)


JUnit will only test those methods in my class that are public.  How do I do junit testing on the ones that are not (i.e., private, protected)?    I can test them by not using junit, but I was wondering what the junit standard method was.

How do I unit test (using xUnit) a class that has internal private methods, fields or nested classes? Or a function that is made private by having  (static in C/C++) or is in a private () namespace?  It seems bad to change the access modifier for a method or function just to be able to run a test.


Is there any other way to bind data type through IN clause using PreparedStatement(datastax)?  Query looks like that:  SELECT * FROM table WHERE day IN(?)   Day is a date type. There will be N elements (up to user).    It is impossible to bind List of days due to exception which say   Codec not found for requested operation: [date <-> java.util.ArrayList]    According to post  the only possible way I can see now is the first one - execute for each value but I would not like to do that. It may extend response time to unacceptable value.   Here is how I execute query:  ResultSet rS = dataSource.executePreperedStatement(query, day); private ConcurrentHashMap<String, PreparedStatement> queryToPrepStmt; public ResultSet executePreperedStatement(String query, Object... values){         PreparedStatement pS = null;         if(queryToPrepStmt.containsKey(query)){             pS = queryToPrepStmt.get(query);         } else{             pS = session.prepare(query);             queryToPrepStmt.put(query, pS);         }         if(pS!=null){                 BoundStatement boundStatement = pS.bind(values);                 return session.execute(boundStatement);         }         return null;     }

What are the best workarounds for using a SQL IN clause with instances of java.sql.PreparedStatement, which is not supported for multiple values due to SQL injection attack security issues: One ? placeholder represents one value, rather than a list of values.  Consider the following SQL statement:  SELECT my_column FROM my_table where search_column IN (?)   Using preparedStatement.setString( 1, "'A', 'B', 'C'" ); is essentially a non-working attempt at a workaround of the reasons for using ? in the first place.    What workarounds are available?


I would like to draw the following picture. I have tried my best but nothing work. My document class memoir. thanks.

I feel intimidated in learning TikZ. I was wondering if there are some nice materials (or just your replies) at different level:   for providing big picture, which is important to beginners to not lose direction during learning. for comprehensive reference.   Examples are important, but only examples are not always clear for understanding the big picture and organization.


I seem i have put My Texture in the UV Map,but it doesn't show up In the Model itself  I don't really Know blender that well.

I wanted to apply texture on some house following an tutorial, I'm sure I did all what was needed but still don't see the texture.  Here's a screenshot:


I've noticed recently that where in England we say "couldn't care less" in the US the negative is avoided and the phrase becomes "could care less". This is rather jarring because of the contradictory semantics. Can anyone confirm this observation, and shed any light on the difference of usage (if it indeed exists)?

What's the deal with the phrase "could care less"?  Whilst growing up, I've always known people (parents etc) to use the phrase "couldn't care less", but I've also come across people who use the phrase "could care less" to mean the same thing (that is, "I do not care at all about that").  To me "couldn't care less" seems a lot more logical. If I couldn't care less about something, that implies I do not care about it at all. In contrast to this, to my mind the phrase "could care less" seems to indicate "I do care about this to some degree at least", but that's definitely not the meaning intended.  What's going on here? Is my (logical) analysis correct or in error?


How would one write a possessive form for a proper noun that already has an apostrophe-s in it? For example, I want to use the possessive form of "McDonald's" maybe in the sentence "The Market Street McDonald's' employees are friendly."  I realize the possessive form may not be entirely necessary there, but in a case where it is, what is correct?

I don't think this has yet been covered in .  There was , however, it was not specifically talking about the case where the proper noun ends in a plural noun.  Feel free to vote to close if I am wrong.  What is the correct way to make a proper noun ending in a plural noun ending in an "s" possessive?  This frequently happens with corporations, e.g., "Dunkin' Donuts."  Should one work off of the fact that the entity is singular—suggesting Dunkin' Donuts's—or should one work off of the fact that "Donuts" is plural and ending in an "s"—suggesting Dunkin' Donuts'?  I expect that the answer might depend on dialect because some regions refer to corporations in the singular form ("Dunkin' Donuts is a company") while other regions refer to corporations in the plural form ("Dunkin' Donuts are a company").  I am specifically interested in American English, but would be interested in hearing answers for other dialects too.


I'm running Ubuntu 16.04 and would like to invert my touchpad scrolling so that moving my two fingers towards the monitor causes the screen to scroll up. Previously, there used to be an option in mouse and touchpad settings that allowed for this. Similarly, gsettings indicates that touchpad configurations are deprecated. Thoughts?  Edit: the xinput command gives this output:  Virtual core pointer                        id=2    [master pointer  (3)]   ⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]   ⎜   ↳ ImPS/2 Generic Wheel Mouse                id=14   [slave  pointer  (2)]   ⎣ Virtual core keyboard                     id=3    [master keyboard (2)]       ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]       ↳ Power Button                              id=6    [slave  keyboard (3)]       ↳ Video Bus                                 id=7    [slave  keyboard (3)]       ↳ Power Button                              id=8    [slave  keyboard (3)]       ↳ Sleep Button                              id=9    [slave  keyboard (3)]       ↳ Integrated_Webcam_HD                      id=10   [slave  keyboard (3)]       ↳ AT Translated Set 2 keyboard              id=13   [slave  keyboard (3)]       ↳ DELL Wireless hotkeys                     id=15   [slave  keyboard (3)]       ↳ Dell WMI hotkeys                          id=16   [slave  keyboard (3)]     For some reason, I don't see a trackpad listed. I'm on a Dell Latitude E5570 laptop that definitely has a trackpad. Additionally, no mouse and trackpad options appear to support the trackpad.  Also, looking at the directory /usr/share/X11/xorg.conf.d/, I only see these configuration files:   10-amdgpu.conf   10-evdev.conf   10-quirks.conf   11-evdev-quirks.conf       11-evdev-trackpoint.conf   50-synaptics.conf   50-vmmouse.conf                50-wacom.conf   51-synaptics-quirks.conf

Is there any way to enable inverse scrolling like on Mac OSX?


There is complete graph $K_{n}$     Find formula for maksimal number of disjoint to each other $k$-cliques in $K_{n}$. Let denote it as $A(n,k)$   I did some research and i computed a formula: $B(n,k)=\lfloor \frac{{n\choose 2}}{{k\choose 2}}\rfloor$.  I thought that equality $A(n,k)=B(n,k)$ holds for every $n,k$, but i was wrong.  For example:   $A(4,3)=1=B(4,3)-1$ $A(5,3)=2=B(5,3)-1$ $A(6,3)=4=B(6,3)-1$ $A(6,4)=1=B(6,4)-1$   Is this true that $A(n,k)=B(n,k)-1$?  Regards

It is a trivial exercise in the pigeonhole principle to show that if an organization contains $m$ people and forms disjoint committees of $n$ members each, then at most $$\bigg \lfloor \frac{m}{n} \bigg\rfloor$$ committees can be formed.  However, I have recently attempted a seemingly simple variation on this problem: what if the committees need not be disjoint, but no two committees can share more than one member.  It seems like another easy exercise in the pigeonhole principle, but I have been unable to come up with a formula for the largest possible number of committees in terms of $m$ and $n$. Does anyone know of such a formula?


Fatal error: Uncaught exception 'PDOException' with message   'SQLSTATE[42000]: Syntax error or access violation: 1064 You have an   error in your SQL syntax; check the manual that corresponds to your   MariaDB server version for the right syntax to use near ''1235'='1235'   WHERE username='wafflezzz'' at line 1' in   /home/wafflez3/public_html/Project SA Theme/ipn/set.php:14 Stack   trace: #0 /home/wafflez3/public_html/Project SA Theme/ipn/set.php(14):   PDOStatement->execute() #1 {main} thrown in   /home/wafflez3/public_html/Project SA Theme/ipn/set.php on line 14   I get that error when I use this code to change a null value to a value.      <?php session_start(); require "../pdo_connect.php"; $usrname = $_SESSION["username"]; ?> <title>Loading...</title> <?php $checker = $conn->prepare("SELECT * FROM transactions WHERE payer_user=:username AND success='1'"); $checker->bindParam(":username", $usrname); $checker->execute();  while ($row = $checker->fetch(PDO::FETCH_BOTH)) {     $paidscript = $row["item_name"];    $sql = $conn->prepare("UPDATE us SET :script=:script WHERE username=:userr");    $sql->bindParam(":userr", $usrname);    $sql->bindParam(":script", $paidscript);    $sql->execute();     echo "You can now view the script!";     }

Why can't I pass the table name to a prepared PDO statement?  $stmt = $dbh->prepare('SELECT * FROM :table WHERE 1'); if ($stmt->execute(array(':table' => 'users'))) {     var_dump($stmt->fetchAll()); }   Is there another safe way to insert a table name into a SQL query? With safe, I mean that I don't want to do  $sql = "SELECT * FROM $table WHERE 1"


In this program I am trying to return the user input backwards  e.g. Laura would be returned as aruaL, but I am getting [C@11d72ca as my output..       String input = JOptionPane.showInputDialog("Enter name");     Scanner scanner = new Scanner(input);     String name = scanner.next();     scanner.close();      char[] backwards = new char[name.length()];     for(int i = 0; i<name.length(); i++)     {         backwards[i] = name.charAt(name.length()-1-i);     }      JOptionPane.showMessageDialog(null, backwards.toString()); }

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


I would appreciate if somebody could help me with the following problem.     Given the set $A=\{1,2,\dotsc,14\}$, calculate the number of distinct sets $M \subset A$ such that $|M| = 7$ and such that the sum of the elements of $M$ is a multiple of $7$.

The problem is as in the question title. Only one addition - $n$ is not divisible by $5$.  I already have a solution involving permutations, but recently I read about generating functions and I was wondering if this problem can be solved with them.   A similar problem is the following: Find the number of all subsets of $\{1, 2, \ldots, 2015\}$ and the sum of elements in each subset is divisible by 5. The generating function used is $${((1+x^0)(1+x^1)(1+x^2)(1+x^3)(1+x^4))}^{403}.$$  But this function cannot be used for my problem, since we need to count how many elements have been "used" to make the subset. Can anyone help me?


Please tell me how to correctly encrypt the data (username, email, message) sent to the server from sql injections. I can not understand the syntax of the record itself.  My php handler  session_start();  if (isset($_SESSION['captcha']) && $_SESSION['captcha']===$_POST['captcha']){     if (isset($_POST['username']) && isset($_POST['email']) && isset($_POST['message'])){          $username = $_POST['username'];         $email = $_POST['email'];         $message = $_POST['message'];          $db_host = "localhost";          $db_user = "alekspvn"; // Логин БД         $db_password = "123"; // Пароль БД         $db_table = "book"; // Имя Таблицы БД      $connect_db=mysql_connect(HOST, MYSQL_USER, MYSQL_PASS)            or die("No connection with SQL");           mysql_select_db("guests_db",$connect_db);          mysql_query("SET NAMES 'utf8'",$connect_db);          $result = mysql_query ("INSERT INTO ".$db_table." (username,email,message) VALUES ('$username','$email','$message')");         echo json_encode(['success' => true, 'message' => 'Added to db']);     }  } else {     echo json_encode(['error' => false, 'message' => 'Wrong captcha']); }

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I'm using  for local time formatting. It's working fine with initially loaded elements but when the elements are loaded via ajax, the time formatting (moment.js) is not working. My initializing code for moment.js: $(function () {     var htmlLang = $('html')[0].lang;     moment.locale(htmlLang);     $( "[data-time-format]" ).each(function() {         var el = $( this );         switch(el.attr("data-time-format")) {             case "time-ago":                 var timeValue = el.attr("data-time-value");                 var timeAgoStr = moment.utc(timeValue).fromNow();                 el.text(timeAgoStr);                 break;         }     }); });  my ajax loader would look like: $.ajax({         url: "/path/loadData.php",         type: "POST",         data: { jsondata:jsondata },         dataType: "html",         success: function(response) {           $("container").append(response);           //I guess I have to reinitialize moment.js         },         error: function() {           alert("Data not loaded.");         }       });

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I want to show that if an integral domain $D$ has finite characteristic, its characteristic must be prime.   This is easy enough if we assume that $D$ has a unit element, but the textbook I'm using (Herstein, Topics in Algebra) does not require there to be a unit element in an integral domain.

If $R$ is a unital integral ring, then its characteristic is either $0$ or prime. If $R$ is a ring without unit, then the char of $R$ is defined to be the smallest positive integer $p$ s.t. $ pa = 0 $ for some nonzero element $a \in R$. I am not sure how to prove that the characteristic of an integral domain without a unit is still either $0$ or a prime $p$. I know that if $p$ is the char of $R$, then $px = 0 $ for all $x \in R$. If we assume $ p \neq 0 $ and $R$ has nonzero char, and $p$ factors into $nm$, then $ (nm) a = 0 $ , which means $ n (ma) = 0 $. Well $ma \neq 0$, because this would contradict the minimality of $p$ on $a$. But I don't know where to go from this point w/o invoking a unit.   Edit: I had left out the assumption that $R$ is assumed to be a integral domain. This has been corrected.


Okay so I want to know how do I backup and restore iPhone data using ubuntu cause I know I can't download and use iTunes and i know you can get like Linuxplay or something like that but is there something else that's works fine?

This question—how to install iTunes on ubuntu—has been asked many times before on this site, but the answers are all outdated and involve Wine or some other tool that no longer works for the most recent version of iTunes. Put simply, I need to regularly back up and occasionally restore the firmware on an iPhone 6.   I cannot:   dual boot Windows—for some reason installing one OS makes the other unbootable & after days of headache & dozens of reinstalls I’ve decided to just leave Ubuntu be & not try to preserve Windows. Plus “just use Windows” is not really a solution on an Ubuntu forum. use libimobiledevice-dev. libimobiledevice-dev doesn’t let you manage iOS updates or sync music anymore. Buy another phone. This one should be obvious but for some reason some asshat always comments “too bad lmao shouldntve bought an iphone ;P”.


How do you estimate the total time reindexing an entire table will take in PostgreSQL?  I have a large PostgreSQL database, the primary table of which has 15 million records and 100 columns, and 200 indexes.  I'm seeing a problem where, after a night of processes loading data into the table, queries to the table are terribly slow for about 6 hours after the loading ends. However, these queries miraculously become fast again after 6 hours post-load.  Is this temporary slowness caused by Postgres updating indexes in the background?  I was thinking about running a REINDEX on the table immediately after loading ends, but I'm not sure how long this will take, and I'm worried it might take longer than the original load and will only worsen performance.

How do you estimate the total time reindexing an entire table will take in PostgreSQL?  I have a large PostgreSQL database, the primary table of which has 15 million rows with 100 columns and 200 indexes.  I'm seeing a problem where, after a night of processes loading data into the table, queries to the table are terribly slow for about 3-6 hours after the loading ends. However, these queries miraculously become fast again after 6 hours post-load.  Is this temporary slowness caused by Postgres updating indexes in the background? How do I speed up this processing? I can't find any parameters for controlling this.  I was thinking about running a REINDEX on the table immediately after loading ends, but I'm not sure how long this will take, and I'm worried it might take longer than the original load and will only worsen performance.  My table stores dozens of descriptors about a customer, and the indexes (many of them partial indexes) are for speeding up very routine queries run by users.  The database is nearly a terabyte, so I rarely load the entire thing to a dev environment. Instead, I have a script that copies a few thousand records.


I have a practice exam problem that asks to prove or disprove the following statement.     Every continuous bijection between homeomorphic spaces is a homeomorphism.   Now based on everything I know about topology, I feel like I have several ways to show that this is indeed false. But then I started second guessing myself based on the wording of the question. It's kind of hard for me to interpret what this question is really asking.  So we already know that we have homeomorphic spaces $(X,\tau_1), (X,\tau_2)$. But are they really homeomorphic if $\tau_1\neq \tau_2$?  I guess what I'm really confused about is what is meant by homeomorphic spaces precisely. Because I know that a continuous bijection is a homeomorphism if and only if it is open (closed), which is equivalent to saying that a continuous bijection is a homeomorphism if and only if $\tau_1=\tau_2$. But if they had to be equal in order for the spaces to even be homeomorphic to begin with, then can't we argue that any continuous bijection between the spaces has to be a homeomorphism?

I hope this doesn't turn out to be a silly question.  There are lots of nice examples of continuous bijections $X\to Y$ between topological spaces that are not homeomorphisms.  But in the examples I know, either $X$ and $Y$ are not homeomorphic to one another, or they are (homeomorphic) disconnected spaces.    My Question: Is there a connected topological space $X$ and a continuous bijection $X\to X$ that is not a homeomorphism?    For the record, my example of a continuous bijection $X\to X$ that is not a homeomorphism is the following.  Roughly, the idea is to find an ordered family of topologies $\tau_i$ ( $i\in \mathbb Z$) on a set $S$ and use the shift map to create a continuous bijection from $\coprod_{i\in \mathbb Z} (S, \tau_i)$ to itself.  Let $S = \mathbb{Z} \coprod \mathbb Z$.  The topology $\tau_i$ is as follows: if $i<0$, then the left-hand copy of $\mathbb Z$ is topologized as the disjoint union of the discrete topology on $[-n, n]$ and the indiscrete topology on its complement, while the right-hand copy of $\mathbb Z$ is indiscrete.  The space $(S, \tau_0)$ is then indiscrete.  For $i>0$, the left-hand copy of $\mathbb Z$ is indiscrete, while the right-hand copy is the disjoint union of the indiscrete topology on $[-n, n]$ with the discrete topology on its complement.  Now the map $\coprod_{i\in \mathbb Z} (S, \tau_i)\to \coprod_{i\in \mathbb Z} (S, \tau_i)$ sending $(S, \tau_i) \to (S, \tau_{i+1})$ by the identity map of $S$ is a continuous bijection, but not a homeomorphism.


$$\int\limits_0^{\frac \pi 2}\log \sin x dx$$  After applying ILATE  integration did not solve. Please give hint

How to compute the following integral?  $$\int\log(\sin x)\,dx$$    Motivation: Since $\log(\sin x)'=\cot x$, the antiderivative $\int\log(\sin x)\,dx$ has the nice property $F''(x)=\cot x$. Can we find $F$ explicitly? Failing that, can we find the definite integral over one of intervals where $\log (\sin x)$ is defined?


I have a list of employees which I get from database. I need to rearrange the list of employees to have fairness.   for example If I have List<Employee> employees = new List<Employee>();  while (reader.Read()) {     departments.Add(new Department(Convert.ToInt16(reader.GetString("Did"))));     departments[count].Name = reader.GetString("DName");     departments[count].MinEarlyShift = Convert.ToInt16(reader.GetString("Minearlyshift"));     departments[count].MinLateShift = Convert.ToInt16(reader.GetString("Minlateshift"));     departments[count].EarlyShiftStart = Convert.ToDateTime( (reader.GetString("Earlyshift"))); }   now I have list of employees which will always have james in index 0 carter in index 1   but I want to rearrange this so carter may have the index 0 for example. basically shuffle the list.

What is the best way to randomize the order of a generic list in C#? I've got a finite set of 75 numbers in a list I would like to assign a random order to, in order to draw them for a lottery type application.


To my knowledge, at the point when a spring is being extended until the bottom of it is stationary, the electrostatic forces of attraction between the molecules in the spring balance out with the external force exerted on the spring. However, when extending a spring, wouldn't the molecules in the spring simultaneously exert attractions to the end that's being extended? Thus, wouldn't this attraction balance out the applied force and keep the spring unable to be extended at all?

When deforming any spring the deforming force is always greater than the restoring force until equilibrium is reached. So, if a constant deforming force caused an extension in any spring the restoring force will increase until it becomes equal to the restoring force and equilibrium is reached. However, I do not understand how the restoring force even increases with extension. I imagine it is related to the fact that the more we deform a spring the more potential energy it has, but I do not know how exactly this affects the restoring force. An explanation which includes the behaviour of the bonds and molecules in any spring during the deformation is appreciated.


so I have a list of words:  list = [name1, name2, name3,...]   I want to print out the first letter of the second word. How would I go about doing that?  Thank you!

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


Assuming that people's birthdays are uniformly distributed across the 365 days in the year, how many people would you need such that the probability of there being at least one birthday in the crowd for every day of the year is 50%?

The problem is quite simple to formulate. If you have a large group of people (n > 365), and their birthdays are uniformly distributed over the year (365 days), what's the probability that every day of the year is someone's birthday?  I am thinking that the problem should be equivalent to finding the number of ways to place n unlabeled balls into k labeled boxes, such that all boxes are non-empty, but C((n-k)+k-1, (n-k))/C(n+k-1, n) (C(n,k) being the binomial coefficient) does not yield the correct answer.


I am working on Sean Carroll's problem 1.8     If $\partial_\nu T^{\mu \nu} = Q^\mu$, what physically does the spatial vector $Q^i$ represent? Use the dust energy momentum tensor to make your case.   I know this question has been asked and answered  and I understand that answer to a degree, but I'm trying to get it directly from dust and I'm not sure I'm doing it correctly or how to interpret what I'm getting.  The dust energy momentum tensor is  $$T^{\mu \nu}=\rho U^\mu U^\nu$$  Where $U$ is the four-velocity and $\rho$ is the energy density in the rest frame. Therefore what I'm looking at is  $$\partial_\nu T^{i \nu} = \partial_\nu \rho U^i U^\nu = \rho U^\nu \partial_\nu U^i+\rho U^i \partial_\nu U^\nu.$$  To examine the right-hand side of the above expression more simply I will choose to work in the rest frame of the dust. According to Carroll, the definition of dust is "a collection of particles at rest with respect to each other." Therefore, in the rest frame I expect all derivatives of velocity to be zero except the time derivative. Therefore I think I can simplify the above to  $$Q^i=\rho U^0 \frac{\partial U^i}{\partial t}+\rho U^i \frac{\partial U^0}{\partial t}.$$  If this is correct, I'm having some trouble understanding what each expression on the right hand side means. I'm not too sure how to proceed.

I'm trouble with exercise 1.8 of Carroll's Space-Time and Geometry:     If $\partial_\nu T^{\mu \nu} = Q^\mu$, what physically does the spatial vector $Q^i$ represent? Use the dust energy momentum tensor to make your case.    First of all, since the momentum energy tensor of dust $T^{\mu \nu}=\rho U^\mu U^\nu$ is symmetric, one has the energy-momentum conservation law $$ \partial_\nu T^{\mu \nu} = \partial_\nu T^{\nu \mu}  =0.$$ A vector $Q$ is constant in any frame related by a Lorentz transformation, while this isn't the case for the components $Q^\mu$. But here $Q=0$ and hence $Q^\mu=0$ also for every component $\mu =0,\cdots,4$?   Even if a straightforwardly apply the equation: $$ Q^i = \partial_\nu T^{i \nu} = (\partial_\nu \rho) U^i U^\nu + \rho(\partial_\nu U^i)  U^\nu + \rho U^i(\partial_\nu  U^\nu ),$$ doesn't seems to yield something...   Is my first reasoning right ? Otherwise: can someone give me a hint ?  Thanks


I happen to be on Ubuntu 18.04, with GNU bash, version 4.4.20(1)-release (x86_64-pc-linux-gnu) The output of   % compgen -A file -- test-data foobar --   outputs all files/dirs in the current directory as though no token to complete was passed.  However, the call   % compgen -A file -- -- --   correctly outputs either nothing or --* depending upon whether or not there is actually a file/files  --* present. (NOTE: Trying pass '--' using the '-W' parameter doesn't help.  The relevant  and  are identical -      compgen [option] [word]      Generate possible completion matches for word according to the options,  which  maybe any option accepted by the complete builtin with the exception of -p and -r, and write the matches to the standard output.  When using the -F  or  -C  options,  the various  shell  variables  set  by  the  programmable  completion facilities, while available, will not have useful values.      The matches will be generated in the same way as  if  the  programmable  completion code  had  generated  them  directly  from a completion specification with the same flags.  If word  is  specified,  only  those  completions  matching  word  will  be displayed.      The  return  value is true unless an invalid option is supplied, or no matches were generated.   It appears as though the -- parameter works as an optional delimiter to show where the partial begins, but it is also interpreted as an 'illegal option` with regards to the return status.  It's easy enough to put in the extra -- to work as a delimiter so that -- is interpreted correctly, but can I rely on the -- to always be required across different bash versions and/or linux (or unix) systems?

There are some utilities that accept a -- (double dash) as the signal for "end of options", required when a file name starts with a dash:  $ echo "Hello World!" >-file  $ cat -- -file Hello World!  $ cat -file                      # cat - -file fails in the same way. cat: invalid option -- 'f' Try 'cat --help' for more information.   But some of those utilities don't show such an option in the manual page.  The  doesn't document the use (or validity) of a -- argument in any of the OS'es. This is not meant to be a Unix - Linux flame war, it is a valid, and, I believe, useful concern.  Neither cat, mv, ed (and I am sure many others) document such an option in their manual page that I can find.  Note that ./-file is a more portable workaround to the use of --. For example, the source (dot) command (and written as .) doesn't (generally) work well with an -- argument:  $ echo 'echo "Hello World!"' >-file  $ . ./-file Hello World!  $ . -file ksh: .: -f: unknown option ksh: .: -i: unknown option ksh: .: -l: unknown option ksh: .: -e: unknown option Usage: . [ options ] name [arg ...]  $ . -- -file         # works in bash. Not in dash, ksh, zsh. ksh: .: -file: cannot open [No such file or directory]


Does the structure $(\mathbb{R}, + ,*)$ have only the trivial automorphism?

Is an automorphism of the field of real numbers $\mathbb{R}$ the identity map? If yes, how can we prove it?  Remark An automorphism of $\mathbb{R}$ may not be continuous.


We already have badges for posting questions or answers, posting chat messages, reviewing,  etc.  Likewise, some badges can be given when profile views exceed 500/1000/10K etc.

Is there going to be a Popular Profile badge?  Imagine the situation:   when the total unique visitors of some guy's personal profile is greater than 10.000 in a week or something like that he could earn a badge for that.


I am a new to android world. I have a problem with the code. My listview is not displaying ArrayList method. It is returning blank as the value in the listview. What could be the issue to this problem.  here is my db file which has the ArrayList execute select events. This will fetch the data from the database and then display it to listview.   public class UniversityFinderDB  extends SQLiteOpenHelper{  private static final int DATABASE_VERSION= 1; static final String DATABASE_NAME="universities.db"; private static final String TABLE_NAME="universityFinder";  private static final String COLUMN_UNIVID="univId"; private static final String COLUMN_UNIVERSITYNAME="univName"; private static final String COLUMN_SCORE="score";  SQLiteDatabase db;     private static final String TABLE_CREATE = "create table universityFinder (univId integer primary key  not null, univName varchar not null, score integer not null);";  public UniversityFinderDB(Context context) {     super(context, DATABASE_NAME,null ,DATABASE_VERSION); }  @Override public void onCreate(SQLiteDatabase database) {      database.execSQL(TABLE_CREATE);   }    public void executeEventInsert(String name, String score){     String query="INSERT INTO universityFinder(univName, score) VALUES('"+name+"','"+score+"');";     db.execSQL(query); }     public ArrayList<HashMap<String,String>> executeSelectEvents(int input){     String query="select * from "+TABLE_NAME+ " where " +COLUMN_SCORE+" >="+input;     Cursor cursor= db.rawQuery(query,null);     ArrayList<HashMap<String,String>> events=new ArrayList<>();     while (cursor.moveToNext()){         HashMap<String,String> event=new HashMap<>();          String colUniversityId=cursor.getColumnName(0);         String colUniversityIdValue=cursor.getString(0);         String colUniversityName=cursor.getColumnName(1);         String colUniversityValue=cursor.getString(1);           event.put(colUniversityId,colUniversityIdValue);         event.put(colUniversityName,colUniversityValue);         events.add(event);     }     return events; }   @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {      String query = "DROP TABLE IF EXISTS "+TABLE_NAME;     db.execSQL(query); }   }   and the listview class where it'll display the data from the database.  public class ListviewFinderUniversities extends AppCompatActivity {   UniversityFinderDB myDB; ArrayList<HashMap<String, String>> eventData; ListView finderListview;  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_listview_finder_universities);        myDB = new UniversityFinderDB(this);      finderListview = (ListView) findViewById(R.id.finderListView);       myDB.executeEventInsert("UCI","101");      myDB.executeEventInsert("UeI","100");      myDB.executeEventInsert("UgI","105");      myDB.executeEventInsert("UjI","107");      myDB.executeEventInsert("ewI","109");      loadUnivFromDb();  }  private void createUnivAdapter(){     String from[]={"univId","univName"};     int to[] = {R.id.eventId, R.id.evenLabel};     SimpleAdapter adapter = new SimpleAdapter(getApplicationContext(), eventData, R.layout.uni_item_finder, from, to);     finderListview.setAdapter(adapter); }  private void loadUnivFromDb() {     int gre = getIntent().getIntExtra("Gre",0);      ArrayList<HashMap<String, String>> data= myDB.executeSelectEvents(gre);     if(data.size()>0){         eventData=data;         createUnivAdapter();     }else {         Toast.makeText(getApplicationContext(),"NoEvents",Toast.LENGTH_SHORT).show();     }  }   }

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?


I have been trying to solve this integral:- $$\int_0^\infty{\frac{\ln x}{x^2+2x+4}}\cdot dx$$ But I have been unsuccessful so far. I have tried integration by parts ( taking $1/(x^2+2x+4)$ as the second function does not work because it ends of as tan-inverse function which is more compicated to integrate.) taking $\ln x$ as the second function was interesting, I ended up in this dead end:- $$\begin{align} I&=\int_0^\infty{\frac{\ln x}{x^2+2x+4}}\cdot dx \\ &= \left[ {\frac{x\ln x -x}{x^2+2x+4}}\right]_0^\infty + \int_0^\infty \frac{2(x+1)(x\ln x-x)}{(x^2+2x+4)^2}\cdot dx \\&= 2\int_0^\infty \frac{(x^2+2x+4-(x+4))(\ln x-1)}{(x^2+2x+4)^2}\cdot dx \\ &= 2\int_0^\infty\frac{\ln x}{x^2+2x+4}\cdot dx - 2\int_0^\infty\frac{1}{x^2+2x+4}\cdot dx -2\int_0^\infty \frac{(x+4)(\ln x-1)}{(x^2+2x+4)^2}\cdot dx \\&= 2I - \left[\frac{1}{\sqrt{3}} \tan^{-1}{\frac{x+1}{\sqrt{3}}} \right]_0^\infty - 2\int_0^\infty \frac{(x+4)(\ln x-1)}{(x^2+2x+4)^2}\cdot dx \end{align}$$ the function in the second step limits to $0$ so I didn't mention it in the third step. Now I have quartic polynomial at the bottom and don't know how to proceed. I have also tried trigonometric substitution ($ x=\tan\theta$) If possible please try to end this process, I am a high school student so please keep that in mind if you show another method :)

So I came across this question on brilliant.org and didn't know how to go about it: $$\int_{0}^{\infty} \frac{ \ln(x)}{x^2+2x+4} dx $$  I tried to complete the squares in the denominator and then use a trigonometric substitution (with tan) but I didn't get anything beyond that.   How do I do it? Do we need to differentiate under the integral sign here?


Hi ı not using blender very much but ı know something about using. Yesterday ı wanted to make wheel for just fun but when ı duplicate something and wants to move my all meshs moving not ı selected what can ı do for it? Thanks for reading anyway ı hope you can help me ıf you cant no problem :)

I created a thick glass bottle and duplicated the interior faces to make a new object to create the liquid inside.   I went in the edit mode, selected the faces I wanted to copy and duplicated them with ShiftD. Then I pressed P to  separate the duplicated faces.   Now I try to make a duplicate of that liquid to make it flow out of the bottle, and I simply need the duplicate of one face of it. So I go to edit mode and do as I did to make the liquid from the bottle faces... but as soon as I'm back to the object mode and I want to move the duplicated faces, every thing moves with it...   I played around and tried things, and while doing so I realized that if I dupe the liquid object in object mode using ShiftD and press 0 to place it where the original is, they move together if I duplicate it and place it somewhere else so that they are separated.   Also if I pick one of the two separated objects and make it intersect with the other one, release my left mouse button to place it there, and then try to move it again, they both move together, but not at the same speed.  I really don't understand what is going on and I'm sure it's really badly explained, so what I'll do is make a screen capture of my Outliner and record the behavior of the objects and upload those to help you understand.


I have two L series lenses 24-70 and 14mm and am in need of a longer lense (70-200 or 70-300)my question is since I shoot mostly landscape from a tripod is it worth the expense to go to the L series lense vs 4.5/5 type?

The Canon L lenses are much more expensive and presumably much better quality than non-L lenses. What makes an "L" lens? How much better are they over a similar length/speed "ordinary" canon lenses?


I just recently found the following link. I am not sure, is this the other network of Stack Exchange sitess or copy of it. Just have a look.  http://magento.dingding.in/

of Stack Overflow, all content posted on Stack Exchange sites by their users (i.e. you wonderful people) has been provided to the whole universe under . For my fellow non-lawyers, that license basically means:   Anyone can use any Stack Exchange posts at any time without having to ask for permission Making money off of the copied content is permitted You don't even have to copy stuff from here verbatim; you can just use it as a starting point and make whatever edits you want There are just two rules you have to follow:   You have to provide . Simple links to the original post and author info are just fine. You have to  and allow other people to use your content, as long as they follow these very same rules. How meta!    (If you ever forget any of that, and want to refresh your memory, the license info is linked to in the footer of every page.)  There are, in fact, a lot of people who republish varying amounts of our content for assorted reasons. Unfortunately, there are some Stack Content Republishers Attributing Poorly and/or Excelling at Ranking (SCRAPERs, for short).  In this context, "attributing poorly" means any use that doesn't follow our attribution rules or make any other reasonable attempt at give credit. This can get pretty egregious; I've seen SCRAPERs that not only don't link back to SE originals, but also use fake author info and post dates to make it harder to find originals. By "excelling at ranking," I'm referring to copycat sites that end up higher in Google results than the original SE sites do for the same content. That's not necessarily wrong, but in some cases, it indicates inappropriate SEO hackery.  So, the question is: what can you do if you spot a SCRAPER?


I have used a number of different applications to get what they claim to be a list of all my facebook friends into a .csv file or a similar format.  For some reason, these applications never export all of my friends and the total number of friends listed in the file is always over 100 less than the actual number of friends I have on facebook.  How can I properly export the names of ALL my friends and their details?

I'm admin of several large political pages. Because of this, my profile chronically suffers report-attacks (i.e.; enough number of people falsely report my profile) and make it suspended. This happens in about every six months. Facebook almost always ignores my appeals even if I send my identity paper to them, so it is no use contacting them for a fix. When this happens I lose hundreds of my friends, and it is very cumbersome to remember all of them and add them back.  I want to export a back up of my friend list (in HTML format with their names and hyperlinks to their profiles), so I can add them back by looking at that list.  I know that Facebook has an internal feature that allows you to download your data. I don't prefer using it, because it usually doesn't return back (I tried it several times, I could only get my data once). And if it lets me download my data, it gives a large bulk of messy data which is not I am looking for.  Is there any tool (maybe a userscript or browser extension) for backing up my friend list in Facebook?


Java Pseudo Code  public class Foo{     public void doStuff(){         System.out.println("Kill all humans...");     }     public class Bar{         public Bar(){             Foo.this.doStuff();         }     } }   You can have a nested class access it's outer class instance through <Class Instance>.this, to look properties or variable values or even invoke methods if you wanted WITHOUT having to pass a reference of the outer class instance to the inner class instance (I'm assuming that is the anonymous part?).  Does C# have something equivalent?

Say if I have a dropdown in a form and I have another nested class inside of this class . Now what's the best way to access this dropdown from the nested class?


I'm in the process of creating a visual model of a product made using 2D CAD software. The .svg which I have imported into blender is the file sent to a laser cutter which would out cut across an acrylic sheet wherever there is a path in order to form the shape.  I was wondering if there is a way of cutting the plane such that the result would be similar to what would be carried out by the laser cutter (imagine the resultant shape being cut out of plane using a knife with runs along the path, if that makes sense)  I've tried to use the Boolean modifier to achieve the effect I am looking for but with limited success. It only seems to cut out a small section of the design for reasons which I do not understand:

I'm attempting to cut a hole in a plane. I added a cylinder object, added the Boolean modifier to the plane, selected "cylinder" and "Difference", but no hole is made. The lower half of the cylinder just highlights, moving/deleting the cylinder reveals a hole-less plane.      How can i cut a hole in the plane?


I want to propose a feature:  search for questions based on two tags.  Why is this needed?   There are a lot of tags that are about a topic which cannot be independent.  For example, let's assume I'm a C# programmer, who is master at arrays.  Let's say I want to answer a C# question about arrays. How can I find one? I can search for a question in the  tag, however, the chances of me finding a question about  are very small. Sure, I can go ahead and search in the  tag, but then I will also find questions about Python arrays, Java arrays, JavaScript arrays and so on.  To sum up:  So the fact that it is impossible to search based on a question with two tags or more is preventing peoples with knowledge about a specific topic to reach people with then same-topic questions

How do I search for questions with specific tags?       For more information about searching, see "" in the .


I have a 64 bit Lenovo Z570 laptop with an Intel i5 processor. Until recently, I've been solely running linux mint on it without problems (the laptop shipped with windows 7). Yesterday I decided to do a clean re-install of a new version of linux mint. I installed it with a live usb drive.   When I restarted the computer after installation, Linux mint wouldn't load. Instead, I get an error after maybe 15 seconds saying "PXE-E61: Media test falure, check cable," preceded by a few other lines referencing Intel UNDI and some patents, returning to the boot menu after a second.  More interesting is when I try to boot a live USB stick with Debian on it. If I try to run it from the boot menu, it waits a few seconds, and then displays the same check cable error as before, and then returning to the boot menu. More interesting is that if I pull out the USB stick after I get to the boot menu, and then try to boot the USB stick, the exact same results occur. The results of trying to boot the USB seem to be independent of if the USB is plugged in or not. I know my live USB stick is good because I've tested it on other similar machines.  My BIOS is Pheonix SecureCore Tiano. People elsewhere say that it is very buggy, I suspect it may be part of the problem. I also re-partitioned my drive during installation of Linux Mint yesterday, making the main partition a little smaller and growing my boot partition by a few megabytes (the new version of mint wanted the boot partition to be at least 100mb to install, so I had to change it as mine was only 90mb). I don't know if this could be a part of the problem or not.  Also, I just threw an ancient windows XP installation CD into it, and it started loading windows setup. It encountered errors, though, and terminated. Any help would be appreciated.

My computer no longer boots Windows or the installed operating system. Instead, I may get this error:  PXE-E61: Media test failure, check cable -or- Check cable connection!  PXE-M0F: Exiting PXE ROM.   and/or one of the following messages or similar:  Operating System not found  No boot device available- No bootable devices--strike F1 to retry boot, F2 for setup utility  No bootable device -- insert boot disk and press any key  No Boot Device Found. Press any key to reboot the machine  Default Boot Device Missing or Boot Failed  Reboot and Select proper Boot device or Insert Boot Media in selected Boot device   What does this mean and what can I do?     This question comes up often and the answers are usually the same. This post is meant to provide a definitive, canonical answer for this problem. Feel free to edit the answer to add additional details.


I edited a fresh apache config file in CentOS 5 using gedit. When I looked at the directory I saw now two files:  httpd.conf    and   httpd.conf~   What does the ~ signify?

At the end of a makefile I saw   rm -f *~ *.class   I understand the *.class, but what's *~?


If $p(x) \in F[x]$ is of degree $3$, and $p(x)=a_0+a_1x+a_2x^2+a_3x^3$, show that $p(x)$ is irreducible over $F$ if there is no element $r\in F$ such that $a_0+a_1r+a_2r^2+a_3r^3 =0$.  If $p(x)$ is reducible, then there exists $ax + b$ such that $a, b \in F$ and $a\ne 0$. And $p(x) = (ax + b)(cx^2 + dx + e)$. Then an $r$ exists such that $p(r) = 0$. Is that how you're supposed to tackle it?

Question:  If $p(x) \in F[x]$ is of degree $3$, and $p(x)=a_0+a_1x+a_2x^2+a_3x^3$, show that $p(x)$ is irreducible over $F$ if there is no element $r\in F$ such that $a_0+a_1r+a_2r^2+a_3r^3 =0$.  My understanding: If $p(x)$ is reducible, then there exists $ax + b$ such that $a, b \in F$ and $a\ne 0$. And $p(x) = (ax + b)(cx^2 + dx + e)$. Then an $r$ exists such that $p(r) = 0$. Is that how you're supposed to tackle it? I understand that I am supposed to first explain the argument for a polynomial of degree 1, but I do not understand how to go about that, and why that helps.


Let $\{y(n)\}$ a sequence of reals (or complex) numbers such that $\sum_{n = 1}^{\infty} x(n) y(n)$ converges for all $\{x(n)\} \in c_0$ (it means $\lim_{n \to \infty} x(n) = 0$). Then I have to show that $\{y(n)\} \in l_1$, it means $\sum_{n = 1}^{\infty} |y(n)| < \infty$. Should I have to replace $x(n)$ by a concrete sequence to show it? Thanks

Let $(y_n)\subseteq\mathbb{C}$ a sequence such that $\sum_{n=1}^{\infty}x_n\overline{y_n}$ converges for every $(x_n)\in c_0$. ($c_0$ is the space of complex sequences converging to zero with the $\infty$-norm.) Show that  $\sum_{n=1}^{\infty}|y_i|<\infty$. Hint: uniform boundedness theorem.   Since $c_0$ is a Banach space, in order to use the uniform boundedness theorem we need linear bounded operators $T_n:c_0\to \mathbb{C}$. My first guess was:  $$T_n(x)=\sum_{i=1}^nx_i\overline{y_i}$$  Clearly every $T_n$ is linear but to prove $T_n$ is continuous seems to be the same as to prove what we actually desire.   Would anyone give me a hint about how to define the family of bounded operators, in order to use the theorem?  Thank you.


One considers certain operations, called elementary row operations, that are applied to a matrix $A$ to obtain a new matrix $B$ of the same size. These are the following:  exchange rows $i_1$ and $i_2$ of $A$ (where $i_1\neq i_2$); replace row $i_1$ of $A$ by itself plus the scalar $c$ times row $i_2$ (where $i_1\neq i_2$); multiply row $i$ of $A$ by the non-zero scalar $\lambda$.  Naturally this operations can be implemented on a column and so we would call the analogous operations on the columns "elementary column operations". Theorem If $B$ is the matrix obtained by applying an elementary row/column operation to $A$, then these two matrix has the same rank. Unfortunately I'm not able to prove the previous theorem, so could someone help me, please?

I have shown that two of the three elementary operations will not change the image of the row space of the matrix: given a row vector $\vec{v}$, $k\vec{v}$ will span the same (scalar multiplication), and switching the order of the rows won't change anything because the span of the row vectors will be the same (vectors will be in a different order). However, how would one show that adding/subtracting vectors does not change the row space?


I'd like to use subprocess on the following line:  convert ../loxie-orig.png bmp:- | mkbitmap -f 2 -s 2 -t 0.48 | potrace -t 5 --progress -s -o ../DSC00232.svg   I found thank to other posts  but in the example we use only twice pipe.  So, I try for two of the three commands and it works  p1 = subprocess.Popen(['convert', fileIn, 'bmp:-'], stdout=subprocess.PIPE) # p2 = subprocess.Popen(['mkbitmap', '-f', '2', '-s', '2', '-t', '0.48'], stdout=subprocess.PIPE) p3 = subprocess.Popen(['potrace', '-t' , '5', '-s' , '-o', fileOut], stdin=p1.stdout,stdout=subprocess.PIPE) p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p3 exits. output = p3.communicate()[0]   Can you help me for the third command?  Thank you very much.

How do I execute the following shell command using the Python  module?  echo "input data" | awk -f script.awk | sort > outfile.txt   The input data will come from a string, so I don't actually need echo.  I've got this far, can anyone explain how I get it to pipe through sort too?  p_awk = subprocess.Popen(["awk","-f","script.awk"],                           stdin=subprocess.PIPE,                           stdout=file("outfile.txt", "w")) p_awk.communicate( "input data" )   UPDATE:  Note that while the accepted answer below doesn't actually answer the question as asked, I believe S.Lott is right and it's better to avoid having to solve that problem in the first place!


I have an old SLR film camera lens with a focal length of 58 mm mounted on my Micro 4/3 camera with a crop factor of 2. How does mounting the lens on a different sized sensor change the effective focal length? I know an x mm lens for my sensor works as 2*x mm fullframe equivalent, but I am not sure about the math in this case.

I'm reading that a 50mm lens is recommended as a first prime lens for DSLR owners as it's supposed to give a 'natural' perspective, but when used on (most) DSLRs, the view is cropped, as if you were zoomed in by 1.5-1.6x, so it's more of a telephoto lens when used on a DSLR. I've also read however that the 50mm lens gives the same perspective on a DSLR and a 35mm, and shouldn't really be considered to be 'equivalent' to an 80mm lens as the crop factor isn't really a magic focal length changer.  Can someone explain how the image is different from (for example) a 50mm lens on a DSLR and an 80mm lens (assuming 1.6x crop factor) on a 35mm camera?


Let A be an $n \times n$ matrix with complex entries $$z_{ij} = a_{ij} + I*b_{ij}$$ If AR is its $2n \times 2n$ decomplexified matrix, i. e. the matrix with entries $a_{ij},b_{ij}$  Is it possible to compute det(AR) from det(A) or viceversa?

If $A$ is an $n\times n$ complex matrix. Is it possible to write $\vert \det A\vert^2$ as a $2n\times 2n$ matrix with blocks containing the real and imaginary parts of $A$?  I remember seeing such a formula, but can not remember where. Any details, (and possibly references) for such a result would be greatly appreciated.


I am tasked to create a simple chatbot that enables a user to create questions and answers, which will then be stored into two arrays. Hence, whenever the user input the same question, the chatbot will be able to print out the answer.  For example, My intended run is:  Bot: 1st question that you want to create. User: What is my name? Bot: and the response is? user: Tom Bot: 2nd question that you want to create. user: How tall am I? Bot: and the response is? You: 179cm You: How tall am I? Bot: 179cm You: What is my name? Bot: Tom  Below is my source code:  public static void main(String[] args) {         String reply = "";        String[] storeQuestions = new String [100];        String[] storeAnswers = new String [100];         do {              /* first question*/             System.out.println("Bot: 1st question that you want to create.");             Scanner input = new Scanner (System.in);             System.out.print("You: ");             String createQuestion = input.nextLine(); // change to string             System.out.println("Bot: and the response is?");             System.out.print("You: ");             String answer = input.nextLine();              /* storing question and answer into the two arrays */             storeQuestions[0] = createQuestion;             storeAnswers[0] = answer;              /* second question */             System.out.println("Bot: 2nd question that you want to create.");             System.out.print("You: ");             createQuestion = input.nextLine();             System.out.println("Bot: and the response is?");             System.out.print("You: ");             answer = input.nextLine();              storeQuestions[1]= createQuestion;             storeAnswers[1] = answer;             System.out.print("You: ");             reply = input.nextLine();              if(storeQuestions[0]==createQuestion) {                 System.out.println("Bot: "+storeAnswers[0]);             }             else if ( storeQuestions[1]==createQuestion) {                 System.out.println("Bot: "+storeAnswers[1]);             }         }while(reply!="bye");                }       }

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?


Is there a tool that is   WYSIWYG and not latex (in fact any coding) base online (for ease of collaboration) Can write math equation Does line numbering Does equation numbering   Google Doc is perfect for 1-3, but they don't support 4-5 (unless you work around by using tables, but that's not really a nice solution)  Authorea and Overleaf does 2-5, but is very latex/code based. (Despite Overleaf's rich text editing mode, which is a step closer to what I want, but still quite far from the goal)  (At the moment, I am just using Google Doc and do all the numbering post exporting to .doc)  ---------This is not the same question as ------------  Reasons:   The author of that question clearly wants to use latex for his part of the collaboration, but wants a non-latex front end for his no-latex using collaborators. Unlike him, apart from writing equations, I have absolutely no intention of using any latex code. In fact, I will be satisfied with MS word type equation editor (as long as it lets me put equation number on it) The accepted solution to that post includes solution like overleaf and Authorea, which I specifically said is not satisfactory to me because they are too latex based. Another population solution to that post was Lyx, which clearly fails the 'Online' part of my question.   At risk of repeating myself, let me say this. That post is after a masked latex service. Whereas I am after a Google Doc with line and equation numbering feature. If I insert a table, I want to insert a table, not a \begin{tabulate\table} environment, if I insert of picture, I want to be able to drag and adjust its position. I want a truly WYSIWYG editor.

Background: I work in a field where the use of LaTeX is common but still far from universal. So far I have been lucky in that all my coauthors in the past have been fellow LaTeX users, so collaboration boiled down to creating a shared Dropbox folder with the .tex and .bib files we were working on. Now I'm starting a collaboration with two colleagues who use Word, so they have proposed to collaborate with Google Docs. There are various reasons why this is a bad idea, the main one being that writing this paper is going to require doing things that are easy in LaTeX but difficult and time-consuming in Google Docs (or in a standard word processor, for that matter) ---e.g., Greek letters for variables, assorted math/logic symbols, trees (in the graph-theoretic sense), or frequent crossreferencing in the running text of numbered examples.   Conflict: One of my colleagues has already said he has no interest in learning LaTeX. On the other hand, I don't want to go hunting through the Google Docs character map every time I need to insert a non-Latin character.   Question: Is there any collaborative writing software that allows including LaTeX tags and environments in a Word-like document? For example, when I'm writing semi-informal things like lecture notes, I can get by with markdown and then generate a pdf with pandoc. I don't know of any online services with similar functionality.


Our company have a IDC (Internet Data Center), and in our IDC, there are many host machines, every host has 1-3 IPs.   There is a situation, such as one host machine has 3 IPs(eg. 102.23.33.1 -> 102.23.33.3). (means in the host machine, have configured the IPs to it)  If the host machine only use 102.23.33.1, and there free out the 102.23.33.2 and 102.23.33.3. We want to find out the free IPs.  How can I do that? I tried to use the forloop to ping the whole IPs, but this is not accurate, because some host machine are baned  for ping.    EDIT  I means the host machine if has 3 IPs, and all can ping them, but the host machine only use the first IP to connect with public network, how can I find the other 2 IPs host machine do not use (or do not often use)?    EDIT-2  I mean the IPs all configured on the OS but may not be actually using them.    EDIT - 3  So, all the before, there can be understood as bellow:  I have a Router, and under it, there are many host machines, and every host machine have some IPs, and how can I record the IPs that go through the Router everyday.  Is there a tool for record the IPs which get through the Router? Or how can I realize my requirement ?


I have an ASUS EEE PC 2G Surf netbook, Celeron M CPU 800MHz, 504 MB RAM, 2 GB TIF card as drive E and 2 GB soldered HDD. I have Win XP OS installed.   Unfortunately, due to recent security updates, it now has only 224 KB of free space left on the HDD. I'd like to install a minimal OS on this; so, I can use the netbook to stream music only. Will delete Win XP and replace with linux.  I am completely new to linux/; so, I have no idea where to start. Is there a small enough version of Ubuntu that I can use on this netbook, and how do I download and install it?   Any help is greatly appreciated.

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


Hi I am struggling to understand exactly what recursion is, It is a requirement of the program I am writing(a snake game) and I cannot find a clear definition of what is classified as recursion. Could someone tell me if the code below is an example of this?  while True:     #recieve input     player_name = input("Enter a name between 0 and 20 characters: ")     #if length is within boundaries the loop is stopped     if len(player_name) > 0 and len(player_name) <= 20: break     #if the name is outwith the boundaries a message is printed and the loop restarts     print("Too long/short, try again.")

How can I build a recursive function in python?


I have a used note 4 and want to make sure there is no spyware or malware on it. I know some can survive a factory reset. Somebody told me to flash a rom and recovery image but not how to do this. I searched and came across a video of a person using a program called odin to do this, however after he was finished all his apps were still there. If this completely cleans the phone why are his apps still there?   What would be the best way for me to actually wipe everything on the phone?

I purchased a used Note 4 off ebay and want to make completely sure there are no spy apps or malware on it. I know some spy apps can be installed into the system partition and survive a factory reset. I discovered an app called cerberus that could do this and could be used to spy on me and blackmail me. How do I completely clean my phone of all spy apps or malware and completely wipe everything including the system partition erasing everything.


While working on an online tutorial I probably messed up my etc/apt/ folder as every time I use apt or apt-get command I get the following error:  E: Type '&&' is not known on line 1 in source list /etc/apt/sources.list.d/kubernetes.list E: The list of sources could not be read. E: Type '&&' is not known on line 1 in source list /etc/apt/sources.list.d/kubernetes.list E: The list of sources could not be read.   Any help please

Every once in a while I see users having issues to update due to errors like this:  E:Type 'ain' is not known on line 1 in source list /etc/apt/sources.list.d/some-ppa.list'   with varying types/line numbers/source list files (often after removing a PPA).  How can such an error be fixed?


Some websites, for reasons I'll never understand, implement links using JavaScript in the onclick event, like this:  <div onclick="document.location='/target_url';">   This doesn't allow me to open it in a new window, either by middle-clicking or even right-clicking and selecting "Open in new tab" in the context menu. Is there a way to allow this, either in Chrome or Firefox on Windows? For example, maybe there is some extension that can rewrite the HTML according to certain patterns, a bit like the Stylish extension does for CSS?

Some websites use "creative" (javascript?) hyperlinks which break browser functionality, such as the ability to  ctrl+click or middle click links to open them in a new tab.  A common example, taleo HR websites   No matter what I try, I can only follow links by clicking on them normally; I can't open them in a new window. Is there any way around this?


I've just been installing DDE on ubuntu and I accidentally chose lightdm over gdm3.  What do I do?

How do I switch from the default display manager (Lightdm) to the older display manager (GDM)?


Problem Statement     If $F(z)$ is analytic in a domain $D$, is $\overline{F(\overline{z})}$ also analytic in $D$?   My Try  Suppose that $F(z)$ is analytic in a domain $D$.  It follows that $F$ is differentiable at each $z \in D$.  I know that the partial derivative $$\frac{\partial F(z)}{\partial \overline{z}} = 0,$$ since $F$ is differentiable at each point $z \in D$. What I am having trouble with is how to get an expression for $F(\overline{z})$.  Question     Of course, I cannot conclude at once that $\overline{z} \in D$ also holds.  Or can I?  Is this even the correct approach to the problem?  If not, how do I solve this conundrum?  Hints will be most welcome!

Suppose $f$ is an analytic function on a domain $D$. Then I need to show that $\overline {f(\bar z)}$ is also analytic.  Here is what I did -   Suppose $f(z) = u(x,y) + iv(x,y)$ where $u$ and $v$ are real functions of $x$ and $y$ and $z = x + iy$. Now $f(\bar z) =  u(x,-y) + iv(x,-y) $ and then $\overline {f(\bar z)} = u(x,-y) - iv(x,-y) $.   To show that a function is analytic, I need to verify that it satisfy Cauchy-Riemann Equations. I differentiated $\overline {f(\bar z)}$ and checked that it actually satisfies these equations. But here is my doubt - Being analytic means that the function if complex differentiable. Now here to check for analyticity, I am differentiating my function without proving that it's actually analytic. So is this the right way to do it?


Let $M$ be an $n$-dimensional compact connected orientable smooth manifold. Can we always find a diffeomorphism $$M\setminus S_1\cong\mathbb{R}^n\setminus S_2$$ where $S_1\subset M$ and $S_2\subset\mathbb{R}^n$ are subsets of measure zero?

I observed some naive examples. Spheres, for example, when we cut out one point, can be embedded into $\mathbb{R}^n$. And if we cut out a measure zero set of a projective space, it can be embedded into the Euclidean space of the same dimension. So I wonder if all manifolds can be embedded into a same dimensional Euclidean space when we cut out a measure zero set? Can anyone prove it or disprove it by giving me some counterexamples?


Note: There is another post on Stack Exchange but that post does not have any proof, just mere verification. I need your help to prove the statement in the title. Here is what I have got so far:  $|a_n^2-a^2|\leq(|a_n|+|a|)|a_n-a|;$ Since $\{a_n\}$ is a sequence in $\mathbb{R}$, the sequence is bounded. That is, there exists $M\in\mathbb{R}$ such that $M\geq a_n$ for all $n\in\mathbb{N}$.  Based on this, could anyone please suggest to me the way forward and also how I can apply the proof for this claim to prove that $\lim_{n\to\infty}a_n^3=a^3$ provided the same assumption. Thank you very much. Nick

Let $\{x_n\}_{n=1}^\infty$ be a squence of nonnegative real numbers such that $\displaystyle \lim_{n \to \infty} x_n =x \in \Bbb R$. If $\alpha \in (0, \infty)$, is it true that $\displaystyle \lim_{n \to \infty} x_n^\alpha =x^\alpha$?  I read the proofs for $\alpha$ integer and for $\alpha=1/2$, but I wonder what happens with the other cases.


When an electron moves at a high speed, it has a large kinetic energy.  I know that E = mc^2 and so if an electron was travelling at a high speed, wouldn't the mass decrease in order to increase the kinetic energy (as smaller masses travel faster)? Where does the energy come from to increase the mass; if the energy came from the kinetic energy of the electron, this would cause the electron to travel slower?

I'm reading Nano: The Essentials by T. Pradeep and I came upon this statement in the section explaining the basics of scanning electron microscopy.     However, the equation breaks down when the electron velocity approaches the speed of light as mass increases. At such velocities, one needs to do relativistic correction to the mass so that it becomes[...]   We all know about the famous theory of relativity, but I couldn't quite grasp the "why" of its concepts yet. This might shed new light on what I already know about time slowing down for me if I move faster.  Why does the (relativistic) mass of an object increase when its speed approaches that of light?


I recently ran updates on Xubuntu 18.04. Now if I go to a text-mode TTY, here's what happens:   Type anything as a username, just can't be empty. Press Enter. It behaves as if Enter is held down, immediately failing logon (as password is empty). After 5 failures, it clears the screen and no longer acts as if Enter is held down.   If I run physlock it just immediately acts as if Enter is held and fails infinitely.  Kernel version 4.15.0-43 works fine, but 4.15.0-44 and 4.15.0-45 are broken. The recovery root shell is unaffected, even when I run login from within it.

I upgraded from 16.04 to 18.04. When I press Ctrl+Alt+F3 I get the terminal which prompts for the username. When I type my username and press Enter, it doesn't wait for my password (its as if I pressed Enter without entering anything). Even if I enter something, the text shown in plaintext and then it keeps on saying my password is wrong. After few times, the screen is cleared and it prompts for my username again and the same loop goes on.


We know that non-conservative forces like friction is a dissipative force.  But according to my book when a solid cylinder is rolling down a rough inclined plane of inclination angle $\theta$ the friction is not dissipative. Why is it so?

I am confused by rolling friction.  Suppose you have a cylinder rolling which starts at rest at the top of an incline plane and begins to roll down the plane without slipping. Is work done by the incline on the cylinder?   I know from doing some problems that the total kinetic energy (translational and rotational) is $mgh$, which is true only if the only work done on the cylinder is by gravity. But also, the cylinder must have nonzero angular acceleration, so friction must be exerting torque on the cylinder, so work must be done by friction. One of these statements is wrong.


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


The energy required to remove an electron from the surface of a metal is less than that required to remove an electron from a free atom. Why?The electron is bound to the nucleus in an atom by electrostatic forces. How is an electron 'free' on a metal surface?

In a particular textbook, the work function of a metal (in the context of the photoelectric effect) is defined as:     the minimum amount of energy necessary to remove a free electron from the surface of the metal   This sounds similar to ionisation energy, which is:     the amount of energy required to remove an electron from an atom or molecule in the gaseous state   These two energies are generally different. For instance, Copper has a work function of about 4.7eV but has a higher ionisation energy of about 746kJ mol-1 or 7.7eV.  I've sort of figured it's because the work function deals with free electrons whilst ionisation is done with a valence electron still bound within the atom. Is the difference due to the energy required to overcome the attraction of the positive nucleus?


In an exercise I'm asked the following:  a) Find a formula for $\int (1-x^2)^n dx$, for any $n \in \mathbb N$. b) Prove that, for all $n \in \mathbb N$: $$\int_0^1(1-x^2)^n dx = \frac{2^{2n}(n!)^2}{(2n + 1)!}$$  I used the binomial theorem in $a$ and got: $$\int (1-x^2)^n dx = \sum_{k=0}^n \left( \begin{matrix} n \\ k \end{matrix} \right) (-1)^k \ \frac{x^{2k + 1}}{2k+1} \ \ \ + \ \ C$$ and so in part (b) i got: $$\int_0^1 (1-x^2)^n dx = \sum_{k=0}^n \left( \begin{matrix} n \\ k \end{matrix} \right) \ \frac{(-1)^k}{2k+1}$$ I have no clue on how to arrive at the expression that I'm supposed to arrive. How can I solve this?

Let $(I_n)_{n \geq 1}$ be a sequence such that: $$I_n = \int_0^1 (1-x^2)^n dx$$  Find the value of $I_n$ (The solution is $\frac{2}{3} \cdot \frac{4}{5} \cdot ... \cdot \frac{2n}{2n+1}$).  I've tried using the binomial expansion of $(1-x^2)^n$ but I couldn't get the proper answer.  Thank you!


I'm making an animation and I need to use armatures, but I don't know how to make the model move with the bones. I know there is a certain command, but I can't recall it.

I am trying to get an armature to move one limb on a deer I have made. Here is my design process!   I made the body and limbs as separate meshes. I wasn't sure how to create limbs out of the body of the mesh and make them look good. I tried joining  the meshes, creating the armature and setting automatic weights and then moving the armature in pose mode. The mesh would not move with the armature I thought maybe it was because many vertices between the mesh and the limb were crossing so I thought maybe that was why the armature was not moving the limbs I used the cut tool to remove the intersecting mesh on the limb and the body so that there were no intersecting vertices.  I then joined this set of meshes and created a new armature, set the weights to automatic and tried to move the mesh in pose mode and it still won't work.    What should I do? I don't know what else to try. I have been following any other online instructions exactly.  File Link:


How to evaluate  $$\lim_{x\to0}\frac{x^2+2\cos x-2}{x \sin^3x}?$$  I tried using L'Hospital but it seemed that there is an infinite loop of 0/0 form

To Prove $$\lim_{x \to 0}\frac{x^2+2\cos x-2}{x\sin^3 x}=\frac{1}{12}$$ I tried with L'Hospital rule but in vain.


Let $\Omega$ be a bounded domain and let $\phi$ be an injective holomorphic mapping of $\Omega$ to itself.   The proposition I would like to prove is:      If $ \exists a \in \Omega$ s.t. $\phi(a) = a$ and $\phi'(a) = 1$,   $\phi$ must be the identity.   A given hint was: Write the power series for $\phi$ centred at $a$ as:  $$\phi(z)=a+(z-a)+ \text{ higher order terms}$$  and consider $\phi, \phi \circ \phi, \phi \circ \phi \circ \phi, \dots$. Estimate the coefficient of the first nonzero term in the power series after the linear term, assuming that it exists, and show that it must in fact be zero. Unfortunately however, I'm not quite certain how to proceed with this hint.

Let $\Omega$ be a bounded connected open subset of $\mathbb{C}$ containing $0$. Let $f: \Omega \rightarrow \Omega$ be holomorphic and $f(0) = 0$, $f'(0) = 1$. The problem I am working on is to show that $f(z) = z$.  If $\Omega = \mathbb{D}$, then this follows from the Schwarz Lemma. I also know of a solution () which involves looking at the power series coefficients of $f^n := f\circ f \circ f \circ \cdots \circ f$ ($n$ times) and using the Cauchy estimates, but is there a different way of doing this problem that doesn't involve taking the $k$th derivative of $f^n$?


For my own game I'd like to know if any of you have an idea about how some popular RPG games handle XP distribution? What I'd be particularly interested in is how the amount of XP a certain enemy gives the player after it's defeat is determined.   For my game I'm struggling to find a proper algorithm/formular to determine that specific amount, since it's a rather small game with not that many enemies types it might be okay to set a value for each enemy type by hand. At first I was experimenting with a formular which takes certain stats of an enemy and then calculates the amount of XP the enemy is 'worth' but as I already said I could not achieve a satisfying result by this.  Nonetheless it would be interesting to know how large games handle this determination. I'd assume that it's not done by hand because you have too many different enemies but I also might be wrong. If anyone could give me any insights or good reads on this I'd be very thankful.  Another thing I'd be interested in is how the XP gaining for the player with a level difference is handled. For instance: If the player is 10 levels ahead of an enemy he should gain 100% less XP from that enemy. If he is 5 levels ahead he only should get 50%. Of course that's a bit depended on my game and the entire design but would that be a common approach to deal with farming low level enemies and still gaining full XP from that? Or are there other approaches such games usually use?  Thanks for any hints, comments and opinions!

I am currently developing an RPG game with a classic experience-points and levelup mechanic. The player kills monsters, gains experience points, levels up when they collect enough and become stronger.  How do I balance the amount of Exp points necessary for reaching each level and the amount of Exp awarded by each monster on each level?


I think that I got the answer, but am not quite sure whether or not it is correct.   Prove that $a^{25}$ mod 65 = $a$ mod 65 given that $a \in \mathbb{Z}$  I started off by using the Chinese Remainder Theorem (65 = 5 $\cdot$ 13 and gcd(5, 13) = 1) in order to get the following two equations:   $a^{25}$ mod 5 = $a$ mod 5  and  $a^{25}$ mod 13 = $a$ mod 13  After that, I used the theorem that states that:  $a^e \equiv a^{e \textrm{ mod } \phi(n)} \textrm{ mod } n$ if gcd(a, n) = 1  $\phi(5) = 4$ and $\phi(13) = 12$  Applying said theorem to the two equations above:  $a^{25 \textrm{ mod } 4}$ mod 5 = $a^1$ mod 5 = $a$ mod 5  and  $a^{25 \textrm{ mod } 12}$ mod 13 = $a^1$ mod 13 = $a$ mod 13  I know that the theorem states that gcd(a, n) = 1 which isn't necessarily the case, that's why I wasn't sure whether my solution was correct.

I want to know a proof of an alternative form of Fermat-Euler's theorem   $$a^{\phi (n) +1} \equiv a \pmod n$$   when $a$ and $n$ are not relatively prime.   I searched some number theory books and a cryptography book and internet, but there were only proofs of the original theorem  $a^{\phi (n)} \equiv 1 \pmod n$ or in case n=pq which is used for RSA. So I would be very thankful if someone show me a proof or book I should read.


please remove this question.  please remove this question. please remove this question.

When I initially connect to my home network my windows PC is assigned an IPv6 address - however after a few minutes it loses this address! I seem to have similar behaviour on multiple hosts using both wireless and wired connections.  My router is an Asus RT-AC87U.  How could it be losing the IPv6 address? How can I mintor / diagnose this issue?  Update:  Based on @grawity's suggestion below I ran wireshark on this. Sure enough I see a Router Solicitation message and a Router Advertisment message with a Router lifetime of 600 seconds. After 600 seconds my computer drops its Ipv6 address.  What is supposed to happen? Should my host send another Router Solicitation message? Or should the router periodically resend the Router Advertisment message?  Update 2:    says that Router Adverticement messages should be sent periodically.


Reading package lists... Error! W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/google-chrome.list:3 and /etc/apt/sources.list.d/google-chrome.list:4 W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/google-chrome.list:3 and /etc/apt/sources.list.d/google-chrome.list:4 W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/google-chrome.list:3 and /etc/apt/sources.list.d/google-chrome.list:4 W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/google-chrome.list:3 and /etc/apt/sources.list.d/google-chrome.list:4 W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/google-chrome.list:3 and /etc/apt/sources.list.d/google-chrome.list:4 W: Target DEP-11-icons (main/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list.d/google-chrome.list:3 and /etc/apt/sources.list.d/google-chrome.list:4 E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_xenial_main_binary-amd64_Packages E: The package lists or status file could not be parsed or opened.

The computer gave me this output in a window:  E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages E: The package lists or status file could not be parsed or opened.   How can I fix this?


Say I post an answer on a recently asked question, yet a FGITW scenario means that so do about a half dozen other SO users. My answer might get a handful of upvotes, but ultimately someone else gets the green check. Since all of the answers are roughly saying the same thing, I go ahead and delete my answer since it's not really adding anything to the discussion (and the question's already been answered). My question is: what happens to the rep I got from my upvoted question? Do I still get awarded the points even though my answer no longer exists? Is this by design, or will I lose the points on a rep recalc? I'd rather have SO be less cluttered and am willing to delete redundant answers of mine; I'm just interested in the mechanics of how rep works in a situation like this.

What circumstances can cause a question or answer to be deleted, and what does that actually mean?    How can a post be deleted? When can't I delete my own post? Can I still see my post even after it's deleted? Can I see a list of my deleted posts? How can I undelete one of my posts? What does deletion mean for a post? How do votes to delete work? What are the criteria for deletion? What else should I know about deleted posts? If I flag my question with a request to delete it, what will happen?       For more information, see the articles about  and  in the .


I've seen things like  command > out.txt  Sometimes appended with  2&1   But these seem to divert all output or all error streams instead of both displaying and copying the output into the file, which is what I'm trying to do. Do I have any options?

In bash, calling foo would display any output from that command on the stdout.  Calling foo > output would redirect any output from that command to the file specified (in this case 'output').  Is there a way to redirect output to a file and have it display on stdout?


Let $X$ be an infinite-dimensional Banach space, and let $B=\{x\in X: \|x\|\leq 1\}$ be its closed unit ball.   Does there exist a continuous mapping $F: X\to X$ such that the set $F(B)=\{F(x): x\in B\}$ is unbounded?  Of course, such $F$ cannot be a linear operator, so $F$ must be nonlinear.  Thank you very much in advance!

I would like an example of a map $f:H\rightarrow R$, where $H$ is a (infinite dimensional) Hilbert space, and $R$ is the real numbers, such that $f$ is continuous, but $f$ is not bounded on the close unit ball $\{ x\in H : \|x\| \leq 1\}$.  Actually, $H$ could be replaced by any Banach space (but not just a normed space-- that's too easy).  My motivation is that if $f$ is linear, this is impossible; but I have next to no intuition about non-linear functions.  Edit: Here's an example for $c_0$ which is even differentiable (disclaimer: I found it here: ).  Define $f:c_0\rightarrow F$ (where F is your field, real or complex) by $$ f(x) = \sum_{n=1}^\infty x_n^n \qquad (x=(x_n)). $$  You can estimate the sum by a geometric progression, so it does converge.  A bit of checking shows that f is Frechet differentible (so certainly continuous).  But $f(1,1,\cdots,1,0,\cdots)=n$ (if there are $n$ ones) so $f$ is not bounded on the closed unit ball.  What I don't immediately see is how to adapt this to $\ell^2$, say.


I've always removed the cards from the cameras and used a high-speed good quality card reader, and find it totally strange to connect the camera via USB instead.  A comment elsewhere prompted me to rethink this:  I've always done it that way, and years ago the cameras were slow (even pathetically slow, using USB 1.1 speed only!) and connection software was clunky and non-standard.  There are some answers here as recent as 2011 that still bring this up.  and also  addressed in 2010.  Now, cameras can use faster memory cards, but I expect card readers are available, along with even faster cards, that are even faster than the camera's USB connection will support.  So what's the current situation seen by people who do use the camera connection?  Also, the software connection thing has improved, with a standard USB protocol used in cameras (or are they?) and already known to desktop operating systems.  Before, it was noted that running the camera as a reader would drain its battery.  Do they charge the battery now, instead?  So how does the comparison weigh in now?  What are the pros and cons of attaching the camera via USB vs. taking the card out and using a dedicated card reader?

I can download the pictures from the camera using the data cable or I can unplug the card and plug into my PC's card reader. Both work and I couldn't notice big differences in speed or reliability.  What's your take on this?


We are (4) travelers flying from Charlotte, North Carolina (Lufthansa) to Munich, Germany then on to Pisa, Italy.  All will have carry-on bags only. Is 1 1/2 hours enough time to get through customs in Munich?

I'm heading to India next week and have a connection in Munich, Germany. I made the mistake of booking a flight with only an hour and a half layover (freaking out!) and I'm wondering if I'll have to go through customs in Munich or if I can pass right on through.


So we have to evaluate $\int\frac{x^2+1}{(1-x^2)\sqrt{1+x^4}}dx$.  My work-  We can write the integrand as $\frac{(x+1)^2-2x}{(1-x)(1+x)\sqrt{1+x^4}}dx$.  So we wish to deduce $\int\frac{(x+1)}{(1-x)\sqrt{1+x^4}}dx-\int\frac{2x}{(1-x^2)\sqrt{1+x^4}}dx$  So lets write it as $I_1+I_2$.  I tried and I can't evaluate $I_1$.  For $I_2$, I took $x^2=t;\ 2xdx=dt$.  The integral becomes $\int\frac{dt}{(1-t)\sqrt{1+t^2}}dt$.  Okay, now we do $t=\tan\theta; \ dt=\sec^2\theta d\theta.$  $\int\frac{\sec\theta}{1-\tan\theta} d\theta$  Now what to do? Please guide me.?

$$\int{\frac{1+x^2}{(1-x^2)\sqrt{1+x^4}}}\mathrm dx$$   This was a Calc 2 problem for extra credit (we have done hyperbolic trig functions too, if that helps) and I didn't get it (don't think anyone did) -- how would you go about it?


I am writing this sentence:     If you have anyone here, I can give it to him/her, and he/she will transfer them to you.   Have I used them correctly in that sentence, or have I should have said it?  Thanks.

Is money a countable noun?  We had a little/few money left, so we decided to have a meal in a cheap restaurant so that it costs us a few rupees.   Here rupees is the currency of India.  I wonder few rupees make sense. But why we can't use few money here?