Any help greatly appreciated, fairly new to both Ubuntu & linux

Printer MP6150 driver installed itself upon plugging in the printer. Printer is recognized  (lsusb shows it) but does not mount. If the printer is recognized, the driver must be working (or?), but something is blocking the system from mounting the printer. Tried the usual things: power of printer, restart Ubuntu etc.   Listed below result of lsusb and fstab:  hans@kontor-linux:~$ lsusb  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 004: ID 04a9:174a Canon, Inc.  Bus 002 Device 002: ID 1058:1001 Western Digital Technologies, Inc. External Hard Disk [Elements] Bus 004 Device 002: ID 046d:c517 Logitech, Inc. LX710 Cordless Desktop Laser   hans@kontor-linux:~$ sudo cat /etc/fstab [sudo] password for hans:   # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point>   <type>  <options>       <dump>  <pass> proc            /proc           proc    nodev,noexec,nosuid 0       0 # / was on /dev/sda6 during installation UUID=eaf3b38d-1c81-4de9-98d4-3834d674ff6e /               ext4    errors=remount-ro 0       1 # swap was on /dev/sda5 during installation UUID=93a667d3-6132-45b5-ad51-1f8a46c5b437 none            swap    sw              0       0   Here is what I have tried:    Tried the , but no luck so far. However, I connected the printer wirelessly to router on other xp box.  Installing the driver from ppa:michael-gruz/canon doesn't work, but the driver is installed


Since Chrome updated to Version 26 it uses per default a menu design (options, contex menu & fav folder) that needs a litte bit more space.  New design:   Old design:   But this litte bit more space makes the difference for me. I don't like it and want to use the old space-saving menu design. The solution was to start Chrome with the --disable-new-menu-style flag, but this flag no longer works in Chrome 28.  Hopefully there a some other people who also prefer the old and space-saving menu design and help me to find a solution for this problem.

It used to be that the new, super wide, touch friendly context menu style that Google introduced a few versions of Chrome ago could be turned off using the start up flag "--disable-new-menu-style".  As of Chrome 28, this is no longer the case, and as a desktop user it is very irritating to see menus that previously fit in the screen not to do so anymore — I don't think I can get used to it. Is there any way around it? If the flag is gone for good, can the style of the context menus be perhaps edited with custom css like the web inspector?


Recently I’m ready to buy a camera before I always use iPhone to taken photos, that’s okay but I want to start a series career you know, go art direction, street shoot, fashion series etc.  I’m a designer, basically, but I’m a newbie in the photography field. So I’m indeed a bit confused about which camera choose. I really need your help and tips.  However, I use the camera mainly for below directions:   art direction street shooting (yeah I love street photography), travel,lifestyle etc. fashion shooting. I’m also a fashion style blogger,  fashion brands model and also my personal fashion brand model. So I need a camera for a lookbook something like this. taking photo shoots for my work so I can scan to the computer. I draw a lot, make collages, also make some craft objects. But the iPhone shots are not very clear and professional. I’m super love black and white photography. During past time I have taken lots of bw photos via my iPhone. Color photos also my type just more passion for bw though. I’m also passionate for shooting portrait, I’m planning start a long-term ongoing project that self portrait , to capture every moment of myself. I’ll set a mini-photoshoot studio scene in my home(mainly for art direction, work shoot, food styling, self portrait, my clothing line lookbook etc.  so any related accessories and tools recommend would be great as well.   So I have some questions and trying to solve:   based on my above directions, do you have any camera recommend? What’s the most and core points when choosing a camera I should consider? my budget is below $1800, $2000 is my upper limit. So is there any good fit camera? Ideally, I’ll take the camera anywhere while I go out or travel, so I know lighter more better. BUT based on my above directions, do you think should I buy an SLR camera or Mirrorless camera？Any camera recommend? I attached some of my fav photography, please forgive my silly question, but is this possible to see which camera they used? I love these style and color tone too much.  Here the reference :  or, how about buying a second-hand camera body + new lens? If this possible?

I am thinking of buying a camera to learn photography. Most of the time I'll be shooting portraits and landscapes. But I am not sure where I should start. Most of my friends tell me that I should get an entry level DSLR, but I am not sure if I have the persistence and enthusiasm to carry it all day in a backpack. But the camera on my cellphone doesn't seem to be enough to begin with.  So what I want is some expert advice (preferably with professional experience). Can most compact fixed-lens or mirrorless cameras fit the situations I mentioned? Or do I really need to go to a DSLR to get a tool to learn photography?


I have PHP code that takes a XML file that is updated daily and  imports it into a MYSQL database. It was working fine until the other data I realized that players who have apostrophe with in their names weren't in the database. Below I listed the coding I am currently using and a XML example. Any help on this matter would be greatly appreciated  xml example of a player that uses an apostrophe in there name  <player> <playername id="62583">Sa'Belle</playername> <allianceid id="729"/> <allianceroleid id="4749"/> <race id="2"/> </player>   Coding I am currently using       set_time_limit(0); // unlimited max execution time require_once 'kodadb.php';  function Unaccent($string) {     if (strpos($string = htmlentities($string, ENT_QUOTES, 'UTF-8'), '&') !== false)     {         $string = html_entity_decode(preg_replace('~&([a-z]{1,2})(?:acute|cedil|circ|grave|lig|orn|ring|slash|tilde|uml);~i', '$1', $string), ENT_QUOTES, 'UTF-8');     }     return $string; } function getGenDate($file, $elemName,$db) {         $count = 0;     // Open the file     $reader = new XMLReader();     if (!$reader->open($file)) {         die("Failed to open '" . $file . "'");     }     while ($reader->read()) {         if ($reader->name === $elemName) {             $count++;             $doc = new DOMDocument;             $node = simplexml_import_dom($doc->importNode($reader->expand(), true));                 $gendate = $node->datagenerationdatetime;                 return ($gendate);           }      }      $reader->close();      return ($gendate); }  function xmlReader($file, $elemName,$db,$genDate) {     $count = 0;     // Open the file     $reader = new XMLReader();     if (!$reader->open($file)) {         die("Failed to open '" . $file . "'");     }     while ($reader->read()) {         if ($reader->name === $elemName) {             $count++;             $doc = new DOMDocument;             $node = simplexml_import_dom($doc->importNode($reader->expand(), true));             $player['allianceid'] = $node->allianceid['id'];             $player['allianceroleid'] = $node->allianceroleid['id'];             $player['race'] = $node->race['id'];             $player['id'] = $node->playername['id'];             $player["Player_name"] = $node->playername;             if ($player['id'] !== null) {                 $sql = "INSERT INTO `players`(`player_id`, `Player_name`, `alliance_id`, `alliance_role_id`, `race_id`) VALUES ('" . $player['id'] . "','" . $player["Player_name"] . "','" . $player['allianceid'] . "','" . $player['allianceroleid'] . "','" . $player['race'] . "');";                 echo $sql."<br>";                 $db->query($sql);                 if ($db->connect_errno) {                     printf("Connect failed: %s\n", $db->connect_error);                     exit();                 }             }         }     }     $reader->close();     return($count); } $rustart = getrusage();  $db = doDatabase(); $sql = "TRUNCATE TABLE `players`"; $db->query($sql); $file = "./tmp/datafile_players.xml"; $elemName = 'server'; $genDate = getGenDate($file, $elemName,$db);  $elemName = 'player'; $numRows = xmlReader($file, $elemName,$db,$genDate); //echo "Inserted ".$numRows. " records into 'players'.";  function rutime($ru, $rus, $index) {     return ($ru["ru_$index.tv_sec"]*1000 + intval($ru["ru_$index.tv_usec"]/1000))      -  ($rus["ru_$index.tv_sec"]*1000 + intval($rus["ru_$index.tv_usec"]/1000)); }  $ru = getrusage(); echo "This process used " . rutime($ru, $rustart, "utime") .     " ms for its computations\n"; echo "It spent " . rutime($ru, $rustart, "stime") .     " ms in system calls\n";

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?


Please notice that I am not asking why a double value changes into another precision, but how can I make the results to be the same.  I appreciate all the comments and answers below, but I didn't get a solution to my problem.  My question again.  I just met a problem when rewriting the code from C++ to C# of the precision problem in double value,  I have a method to calculate the result of a financial product of several double values, but when I compare the results, I got different but similar results from C++ and C# program due to the precision of the double value.  I debug the program in C++ I found that after I set the values to a and b double a = 4.9; double b = 5.1;  The value of a and b changes to, a is 4.9000000000000004 and b is 5.0999999999999996. But in C#, a is still 4.9 and b is still 5.1, and finally, I got the results of -0.062579630921710816(C++ result), and -0.062579644244387111(C# result)  I am totally new in C# and C++, so are there any solutions to make the calculation result to be the same, please (I cannot change the C++ code)? Or is it possible to make the calculation result to be the same?

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


I am not new to java but just recently practicing about jdbc. I'm trying to fetch data from mysql database and load it to jtable..  here's my code for fetching the data class name FileMaintenance  public DefaultTableModel getProducts() {     DefaultTableModel dtm = new DefaultTableModel();     try{          dtm.addColumn("Product Code");         dtm.addColumn("Description");         dtm.addColumn("Unit Price");         dtm.addColumn("Selling Price");          conn.stmt = conn.conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);         sql = "SELECT prodcode,proddesc,origprice,sellingprice FROM products";         rs = conn.stmt.executeQuery(sql);          while(rs.next()){             String code = rs.getString(1);             String desc = rs.getString(2);             String uprice = rs.getString(3);             String sprice = rs.getString(4);              dtm.addRow(new String[]{code,desc,uprice,sprice});         }         return dtm;     }catch(Exception ex)     {         JOptionPane.showMessageDialog(null,"Unable to fetch data...","Error",JOptionPane.ERROR_MESSAGE);     }     return null; }   and there as the line that I used to call the method from FileMaintenance class  public void UpdateJTable() {     DefaultTableModel model = new FileMaintenance().getProducts();     jtable.setModel(model); }   now when I try to run the app, it says I'm connected to database which is true because I already tried inserting data and its successful, but there's an error occur. the error is related to DefaultTableModel because its point to line  DefaultTableModel model = new FileMaintenance().getProducts(); jtable.setModel(model);   it says:     Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException           at MyForm.UpdateJTable(MyForm.java:119)           at MyForm$1.windowOpened(MyForm.java:104)           at java.awt.Window.processWindowEvent(Window.java:2048)           at javax.swing.JFrame.processWindowEvent(JFrame.java:296)           at java.awt.Window.processEvent(Window.java:2009)           at java.awt.Component.dispatchEventImpl(Component.java:4861)           at java.awt.Container.dispatchEventImpl(Container.java:2287)           at java.awt.Window.dispatchEventImpl(Window.java:2719)           at java.awt.Component.dispatchEvent(Component.java:4687)           at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)           at java.awt.EventQueue.access$200(EventQueue.java:103)           at java.awt.EventQueue$3.run(EventQueue.java:694)           at java.awt.EventQueue$3.run(EventQueue.java:692)           at java.security.AccessController.doPrivileged(Native Method)           at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)           at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)           at java.awt.EventQueue$4.run(EventQueue.java:708)           at java.awt.EventQueue$4.run(EventQueue.java:706)           at java.security.AccessController.doPrivileged(Native Method)           at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)           at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)           at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)           at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)           at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)           at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)       at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)      at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)   could someone please tell me what is the problem with this code?

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?


Show that $[L^2,[L^2,\vec{r}\,]\,] = 2\hbar^2\{L^2, \vec{r}\},$ where $\vec{r} = x\, {\hat x} + y\, {\hat y} + z\, {\hat z}.$  "Edit: $\{A,B\} = AB + BA$ is the anti-commutator."  I am able to solve this by brute force expanding everything, but I was wondering if there is a quicker, more elegant way of doing so.  Also, if anyone has any physical intuition behind what this result means, it would be much appreciated.

This operator identity showed up in a course I was taking, and it was given without proof.  $$[L^2,[L^2,\vec{r}]]=2 \hbar ^2 \{ L^2, \vec{r}\}$$  The curly brackets denote the anticommutator, $AB+BA$. The $\vec{r}$ operator is the position operator. The $L^2$ operator is given by:   $$L^2 = -\hbar ^2 \left( \frac{1}{\sin \theta}  {\partial\over\partial\theta} (\sin \theta {\partial\over\partial\theta}) + \frac{1}{\sin^2  \theta} {\partial^2\over\partial\phi^2}\right)$$   Is there a way of proving this identity without tediously expanding all the commutators? I've been trying to find one but was unable to.


In the answer of another question of mine, I was told that the official version for creating a bootable USB flash drive for Ubuntu is Rufus:    Now, I was just wondering, would the data be lost after every reboot?   Also, I read about the terms persistent and full install.  Would following the official version give me a persistent or full install?

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


Is there a way to define a new command so that existing  \includegraphics[scale=x]{fig_name}   becomes  \includegraphics[scale=x]{fig_name.eps}   for any x and fig_name? This is for automatic conversion of eps to pdf because eps may cause out of memeory issues with xdvipdfmx: .

I'm using Mathematicato produce some of my graphics (when i'm not able to just TikZ them easily). All these images are availabvle as .eps and .pnghaving the same file name - let's use img.eps / img.png in the following.  I would like to set a preference for graphicx to use only one type, i.e. using  \includegraphics[width=.6\textwitdh]{img}   I would like to specify, which img to use with one switch, (package) option or variable.  I tried  \DeclareGraphicsExtension{.eps}   to restrict the allowed image extension to .eps, but still the .png file is included. It seems, .pngis preferred over .eps.  Though this is of course restricted to XeTeX it might be interesting for others, if you use .png together with some lossy format like .jpg to have a file extension preference.   Is there a package option for that or an easy command (global document option) for that?  To provide an MWE is - I think - difficult, because it would be necessary to provide at least 3 files.


It's obvious that for every particle velocity is smooth i.e it cannot undergo sudden finite change in its position in infinitisiminal time.  Similarly any particle's velocity cannot undergo a change instantaneously (Infinite acceleration can't happen, intuitively).  Does this pattern apply to higher time derivatives of position like jerk? If yes then till how much higher derivative? 10th? 100? Infinite?

My thinking:    acceleration corresponds to a force which is instantaneous, so the acceleration of a rigid body can be rather spiky (non-smooth) velocity (angular velocity) describes the ratio of change of the distance(angle), so it is smooth in the real world.   Conclusion, it makes sense to  (e.g., simple averaging) a velocity signal (temporal velocity), but it does not make so much sense to do smoothing on acceleration signal. Am I right?


So, I have a great trouble. When you define a vector for a first time to someone you use the term that two pointed segments are parralel and have the same orientation. So, for that you use in latex upuparrows. But when I try this $AB \upuparrows CD$ it cracs and informs me on some undefined control sequence. This is my first time to work with upuparrows command, so I don't know anything. Please help it's urgent.

I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?


I used to like and think that Halliday and Resnick was the best, but I've heard it is not really advanced. What honors physics textbook would you recommend or is the one most used out there?  Again, I'm looking for a very specific type of book, which is an advanced one for honors physics classes in college. A huge list of all possible physics books is definitely not what I'm looking for.

Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.  All the questions linked below, as well as others which deal with more specialized books, can be found under the tag  (formerly ).  If you have a question to add, please edit it in. However, make sure of a few things first:   The question should be tagged  It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list   Related Meta:


hard disk space lost when I installed Ubuntu 14.04 and also lost all partition and data please help me out. i was installing Ubuntu 14.04 accidentally LOST ALL DATA & drive partitions. i have not try any software for recovery so please tell me how can i recovery all partitions back.

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


On Ubuntu 20.04, I use the gnome tweaks tool to switch caps and escape for improved efficiency with vim-like editing. I am running on a laptop with external keyboard connected. What bugs me is that this works when I just change it but only until I suspend. It is ignored after resuming from suspend. So the caps lock button on the laptop keyboard after resume acts like ESC, as I want, but the caps lock button on the external USB keyboard does not behave the same. The same keyboard and setting with Ubuntu 18.04 on my 2nd laptop work fine. Any ideas how to investigate/fix this? It sounds like a bug!

I have caps-lock key remapped to control, which usually works fine, but after some uptime and one/more suspend/awake cycles* this mapping breaks, and caps-lock reverts back to the default behavior -- i.e. turning on the led and capitalizing whatever I type. (Even though the Tweaks UI still shows it as being mapped to Ctrl -- see picture below.)  Questions:  Is this a known issue (with maybe a known fix)? (Could not find anything relevant with a quick search.) Is there a way to debug the problem, preferably from the command line?  *Remark: I'm not sure it is the suspend/awake cycle that causes the problem, but I can't connect it to anything else... Remark2: removing and readding the mapping (or rebooting) solves the problem, but it would be nice to find a more permanent solution.


I was wondering if any American writers could give me some advice as to whether the following expressions/vocab are used and understood in the US:  (words in bold are the ones I'm asking about. Some words are also in inverted commas)   The living room of a house - is this expression ok? Do you ever say "front room" or "sitting room"? If it's a massive house with a huge entertainment area, can you say "living area"? I was tickled - is this expression ok? It means happy. "My college mate wants to hang out at my digs" - meaning my place, or college dorm. Would digs be used? Is college mate an ok expression for someone you go to college with? In the real world, do people stop on the shoulder or the hard shoulder of a highway or is either fine? Is median strip used for the partition between 2 lanes of a highway going in different directions? "He takes the piss out of every banker he meets" - meaning he mocks them. Is this used? Can you say "I'm pissed off at him" (angry) or does it have to be: "I'm pissed at him." "I called my parents' landline (fixed home phone)." Is landline ok? "I tried on the jeans in the changing room." Is this ok or does it have to be fitting room or something else? Is the word "thingamajig" used in American English? "I can't walk on my ropey leg" - meaning damaged or injured or tired. Can ropey be used? Security guards are surveilling the place. This verb is showing up as misspelt but I see it sometimes. Is there another spelling or verb?   13.In the real world, do people in the US use MPH or KPH as the unit of speed when driving?   Is the expression "Calm my jitters" acceptable? (calm my nerves) If you pull up to a mansion surrounded by a fence with very thick metal bars all around it, is the word "fence" appropriate or is there a better word. I think that gate would only be for a door in a fence or something? Is the expression "It cost a pretty penny" ever used in the US? Is the expression "It took every ounce of strength" used in the US? Can the word "skiff" be used in the US for a sort of flat-bottomed row boat?   Thank you so much to anyone willing to give advice about these points. Though I appreciate any input, I think it would be most useful to hear from actual American writers to avoid possible confusion.   Many thanks!

I was wondering if any American writers could give me some advice as to whether the following expressions/vocab are used and understood in the US:  (words in bold are the ones I'm asking about. Some words are also in inverted commas)   The living room of a house -- is this expression ok? Do you ever say "front room" or "sitting room"? If it's a massive house with a huge entertainment area, can you say "living area"? I was tickled -- is this expression ok? It means happy. "My college mate wants to hang out at my digs" - meaning my place, or college dorm. Would digs be used? Is college mate an ok expression for someone you go to college with? In the real world, do people stop on the shoulder or the hard shoulder of a highway or is either fine? Is median strip used for the partition between 2 lanes of a highway going in different directions? "He takes the piss out of every banker he meets" -- meaning he mocks them. Is this used? Can you say "I'm pissed off at him" (angry) or does it have to be: "I'm pissed at him." "I called my parents' landline (fixed home phone)." Is landline ok? "I tried on the jeans in the changing room." Is this ok or does it have to be fitting room or something else? Is the word "thingamajig" used in American English? "I can't walk on my ropey leg" -- meaning damaged or injured or tired. Can ropey be used? Security guards are surveilling the place. This verb is showing up as misspelt but I see it sometimes. Is there another spelling or verb?   13.In the real world, do people in the US use MPH or KPH as the unit of speed when driving?   Is the expression "Calm my jitters" acceptable? (calm my nerves) If you pull up to a mansion surrounded by a fence with very thick metal bars all around it, is the word "fence" appropriate or is there a better word. I think that gate would only be for a door in a fence or something? Is the expression "It cost a pretty penny" ever used in the US? Is the expression "It took every ounce of strength" used in the US? Can the word "skiff" be used in the US for a sort of flat-bottomed row boat?   Thank you so much to anyone willing to give advice about these points. Though I appreciate any input, I think it would be most useful to hear from actual American writers to avoid possible confusion.   Many thanks!  Follow up questions:  Thanks to all those who gave their very useful opinions. I have a couple more questions for anyone willing to give advice:   What do you call the area (let's say on the 10th floor) in front of an elevator door? Is there a specific word like "the landing"? When you enter a house (without a mud room), there is a space just past the front door which is not really a room, but it's like the entrance way/hallway between the front door and other rooms like the living room, study. Is this called a "hallway"? It's not a lobby, obviously as that would be for a hotel or something. Can it be the "entrance hall"? If you are using WASP-y as an adjective, do you have to write it like "WASP-y" or "WASPy". I'm guessing "waspy" hasn't become a thing yet?   Thank you!


While I know very well the difference between "on" and "in", or even between "on" and "above", I didn't get what the difference between "in" and "at" is, that many specific things strictly get just one of them (such as "at the university", "in the building", "in / at the morning".).   Is there a clear rule where to use this one (at) and where to use the second one (in)?

Let's meet in the morning  or at the morning.  in the afternoon or at the afternoon.  in the night or at the night.  in the park or at the park.  working in the background or at the background.


I am flying from Germany to the USA with a 1 hour and 50 minute layover in Amsterdam Schipol Airport later this month (December 20th).  I know I need to go through some extra security when I arrive in Amsterdam in order to travel to the USA. so will a 1 hour and 50 minute connection be enough time?

Arriving in AMS in a Delta flight from Bombay at 7 AM. Departure at 7.50 AM in a KLM flight flying to Detroit. On a single leg ticket. Is this going to be time enough? Or should one just bolt as soon as the flight lands?  A google just shows the layout of the airport and there don't seem to be dedicated terminals for airlines.  Edit In case the connecting flight is missed. On a ticket which is non refundable (non - everything - as this was the cheapest ticket), what happens when one misses a connection? Whose responsibility are the next steps? What should be the next steps? Reading other questions about AMS, with 50 minutes, it seems that the luggage is sure to be delayed. Sigh.  Edit 2 It's been a while, but when I was transiting, 50 minutes was pretty ample enough.


Does anyone know what the heck is that? Eevee is just broken and I have no idea how to google that

I don't know why but now, when i go in material preview or rendered (in solid mode it works fine), my object is entirely gray, or invisible idk, because it has the same color of the background. I've been working for days on this project without having this issue, it suddenly showed up. I tried opening other old projects and suddenly they all do the same so i guess it is some blender program setting that applies for all the projects, but idk how it happened cuz i didn't change anything :/, anyone got any tips?


The day of the week time is displayed on the top bar... Why isn't the date displayed there, like it was in previous versions??? Why on earth would this capability have been removed???

On previous versions I had the date displayed. Now it just shows the current day but not the day's number or the month.   Is there a way to customize the clock or tray/taskbar more in GNOME shell on Ubuntu 17.10 and later?


I was looking at one of the examples on the Arabic Language proposal, I noticed  to look at their profile, on there I noticed he/she were following the proposal I reopened () but the follower count only says one (me).  Is this a bug? or is it that this user followed the un-followed the proposal and his profile isn't updated?

I know of one person who is following my proposal who doesn't show up on the proposal webpage.    My proposal is for quantitative finance: .  It shows 19 people following the proposal (on the side of the page), and the total listed at the top of the page is 19 followers.  Yet one user is not listed: .  This makes me wonder if other followers are also not being counted?


I have a contentEditable="true" div in which, as I type, I would like to wrap the last word before the caret in strong.  I am trying to use regex for this. I made it work for when I type of the string in the regex statically, but it does not work when I pass the word dynamically via like this:  textBeforeCaret.replace(`/${lastWord}$(?!.*?${lastWord})/`, '<strong>$&</strong>')   Thank you for your help!

I would like to create a String.replaceAll() method in JavaScript and I'm thinking that using a regex would be most terse way to do it.  However, I can't figure out how to pass a variable in to a regex.  I can do this already which will replace all the instances of "B" with "A".  "ABABAB".replace(/B/g, "A");   But I want to do something like this:  String.prototype.replaceAll = function(replaceThis, withThis) {     this.replace(/replaceThis/g, withThis); };   But obviously this will only replace the text "replaceThis"...so how do I pass this variable in to my regex string?


I want to print 10 random numbers from -100 to 100, but my code below always print negitive number. I did not get any answer for this. How to do this ?  import java.util.Random; public class VectorAndList { public static void main(String arg[]){     Random random = new Random();     int number ;     for(int i=0;i<10;i++)     System.out.println(number = random.nextInt(100)+ (-100)) ; } }

How do I generate a random int value in a specific range? I have tried the following, but those do not work: Attempt 1: randomNum = minimum + (int)(Math.random() * maximum);  Bug: randomNum can be bigger than maximum. Attempt 2: Random rn = new Random(); int n = maximum - minimum + 1; int i = rn.nextInt() % n; randomNum =  minimum + i;  Bug: randomNum can be smaller than minimum.


I'm using this code:  import java.util.Scanner; import java.util.Arrays; import java.util.Random;   public class Matrix {     public static void main(String[] args)     {         Scanner enter = new Scanner(System.in);         int[][] firstMatrix = new int[4][4];         int[][] secondMatrix = new int[4][4];         Random spin = new Random();            System.out.println("Please enter 16 numbers to populate the array: ");          for (int count = 0; count<firstMatrix.length;count++) // nested for for user input to populate 4x4 array         {               for (int count2 = 0; count2 < firstMatrix[count].length; count2++)             {                  firstMatrix[count][count2] = enter.nextInt(); // populate array with user input                }          } // end array population              System.out.printf("The sum is: %d%n", sumMatrix(firstMatrix)); // call sumMatrix             System.out.println(firstMatrix[0][0]); // debug                for (int count3 = 0; count3<secondMatrix.length; count3++) // nested for to populate array with random numbers 1-100, row             {                 for (int count4 = 0; count4<secondMatrix[count3].length; count4++) // column                  {                     secondMatrix[count3][count4] = 1 + spin.nextInt(100); // 100 inclusive, generate and populate array                 }             }               System.out.println(secondMatrix[0][0]); // debug to show that it is properly printing the correct element               for (int i = 0; i<secondMatrix.length; i++)              {                 for (int j = 0; j<secondMatrix[i].length; j++)                     System.out.print(" " + secondMatrix[i][j]); // print the total array ( this process can be used to print the returned array )                }          System.out.println(); // debug               int arrayTotal = firstMatrix[0][0] + secondMatrix[0][0]; // debug                 System.out.println("The element total is " + arrayTotal); // debug                     System.out.println();          addMatrix(firstMatrix,secondMatrix); // call addMatrix               System.out.println("Programmed by Stephen Mills");     }  // end main                public static int sumMatrix(int[][] array) // method to sum the elements of the array         {                 int total = 0;                  for (int number = 0; number<array.length; number++) // row                  {                     for (int number2 = 0; number2<array[number].length; number2++) // column                         total += array[number][number2]; // sum of all elements                 }                     return total; // returns the sum          } // end sumMatrix          public static int[][] addMatrix(int[][] array1, int[][] array2) // improper method         {             int[][] thirdMatrix = new int[4][4];              for (int count4 = 0; count4<thirdMatrix.length; count4++)             {                 for (int count5 = 0; count5<thirdMatrix[count4].length; count5++)                     thirdMatrix[count4][count5] = array1[count4][count5]+array2[count4][count5];               }             System.out.println(Arrays.toString(thirdMatrix));             return thirdMatrix;         } // end addMatrix7    }   Most of the program works as intended but I'm getting this "[[I@3d4eac69, [I@42a57993, [I@75b84c92, [I@6bc7c054" output when trying to print my array. I've tried several methods, including simple println, toString, setting a variable equal to the method call, and I've tried putting the print statement in main first and then in the method second. Any ideas why this is happening?

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]


Whether I use the \usepackage[capitalize]{cleveref} or \usepackage{cleveref}, I don't see any difference in the output from \cref.  Do I understand correctly that this option is indented to force \cref to output the capitalized version of the environment name, even if not at the beginning of a sentence?  Here is the LaTeX file I'm using.  \documentclass[a4paper]{article}   \usepackage{xcolor} \usepackage{amsthm} \usepackage{framed} \usepackage[colorlinks=true]{hyperref} \usepackage[capitalize]{cleveref}   \theoremstyle{plain}% default \newtheorem{prototheorem}{Theorem}[section] \colorlet{shadecolor}{orange!15}  \newenvironment{theorem}    {\begin{shaded}\begin{prototheorem}}    {\end{prototheorem}\end{shaded}}  \newtheorem{protolemma}[prototheorem]{Lemma} \newenvironment{lemma}    {\begin{shaded}\begin{protolemma}}    {\end{protolemma}\end{shaded}}  \newtheorem{protocorollary}[prototheorem]{Corollary} \newenvironment{corollary}    {\begin{shaded}\begin{protocorollary}}    {\end{protocorollary}\end{shaded}}  \crefname{theorem}{theorem}{theorems} \Crefname{theorem}{Theorem}{Theorems} \crefname{lemma}{lemma}{lemmas} \Crefname{lemma}{Lemma}{Lemmas}  \begin{document}  \begin{lemma}   \label{ent.201}   If $V$ is a set of subsets of $U$, and $\exists X_0 \in V$ such that   $X \in V$ implies $X_0 \subseteq X$, then $X_0 = \bigcap V$. \end{lemma}  Intuitively, \cref{ent.201} says that given a set of subsets, if one of those subsets happens to be a subset of all the given subsets, then it is in fact the intersection of all the subsets.  \begin{theorem}   \label{ent.188}   If $V \subseteq U$, and if $F$ is a set of binary functions defined on   $U$, then there exists a unique $clos_F(V)$, and it is closed under $F$. \end{theorem}  We can see from \cref{ent.201} and also from \cref{ent.188} such sets are always finite.  \end{document}

This question is similar to (but not a duplicate of)   The original post makes a code example, which does not seem to always reproduce the problem.   Here is a better attempt.  The following code is supposed to output \cref usages as capitalized label names, but it does not really work.  Section is output as capitalized, but definition is output as lower case.  I'd be happy if someone could help me figure out why it doesn't seem to work.  I'm also attaching an image to show that "definition" is given in lower case despite using the capitalize option.    \documentclass[a4paper]{article} \usepackage{pgf}  \usepackage{color} \definecolor{blueye}{rgb}{0, 0.2, 0.5} \usepackage{mathtools} \usepackage[colorlinks=true,allcolors=blueye]{hyperref} \usepackage[capitalize]{cleveref} \usepackage{amsthm} \usepackage{framed}  \newtheorem{protodefinition}{Definition}[section]  \newenvironment{definition}    {\colorlet{shadecolor}{green!5}\begin{shaded}\begin{protodefinition}}    {\end{protodefinition}\end{shaded}}  \crefname{protodefinition}{definition}{definitions} \Crefname{protodefinition}{Definition}{Definitions}  \begin{document}  \section{Introduction} \label{sec.intro}  The problem we examine in this article is that of using Boolean operations to decompose a set of partially overlapping regions into a valid partition.  In particular, given $V=\{A_1, A_2, ..., A_M\}$, suppose that for each pair $(A_i,A_j)$, we whether $A_i \subseteq A_j$, $A_i \supseteq A_j$, or $A_i \cap A_j = \emptyset$.  We would like to compute the maximal disjoint decomposition of $V$.  We define precisely what we mean by maximal disjoint decomposition in \cref{def.mdd} of \cref{sec.1253}.  \subsection{Maximal Disjoint Decomposition} \label{sec.1253}  \begin{definition}   \label{def.mdd}   If $D$ is a disjoint decomposition such that for any other disjoint decomposition $D'$ it holds that $|D| > |D'|$, then $D$ is said to be a \emph{maximal disjoint decomposition}. \end{definition}  \end{document}


After upgrading to Ubuntu 16.10 I am not able to use my laptop because of the high CPU Usage of "kidle_inject".    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                     7966 root     -51   0       0      0      0 S  35.2  0.0   4:27.77 kidle_inject/1              8327 xxxx      20   0 1906104 302952  69876 S  34.9  3.7   0:08.15 chromium-browse             7968 root     -51   0       0      0      0 S  34.5  0.0   4:31.28 kidle_inject/3              7965 root     -51   0       0      0      0 S  33.9  0.0   4:24.68 kidle_inject/0              7967 root     -51   0       0      0      0 S  32.6  0.0   4:28.50 kidle_inject/2               sudo rmmod intel_powerclamp stops the crazy processes but I need to execute it each time after restarting my PC.  Please help me. Thanks.

Whenever kidle_inject starts running on my system the load shoots up. In general it only gets to a load of around this 5.23, 3.65, 2.54 but a lot of the time it jumps up past the 15 mark on each of them. At that point the system grinds to a halt and I have to power it off.  This only happens when the kidle_inject process starts. How can I disable this process so my machine can work and I can get some work done.  Example top:  top - 12:43:48 up  3:02,  3 users,  load average: 6.57, 5.53, 3.33 Tasks: 256 total,   3 running, 253 sleeping,   0 stopped,   0 zombie %Cpu(s):  5.9 us, 16.6 sy,  0.0 ni, 74.7 id,  0.5 wa,  0.0 hi,  2.3 si,  0.0 st KiB Mem:   8080252 total,  7937856 used,   142396 free,   258904 buffers KiB Swap:        0 total,        0 used,        0 free.  4061336 cached Mem    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND 13509 root     -51   0       0      0      0 S  54.7  0.0   3:29.47 kidle_inject/1 13511 root     -51   0       0      0      0 S  54.1  0.0   3:30.92 kidle_inject/3 13510 root     -51   0       0      0      0 S  48.8  0.0   3:11.60 kidle_inject/2 13508 root     -51   0       0      0      0 S  47.6  0.0   3:08.47 kidle_inject/0


How do I find all positive integers $n$ such that $\phi(n) + \tau(n) > n$? I attempted using the formulas for $\phi(n)$ and $\tau(n)$, but I feel this approach is kind of handwavy...

Find all positive integers $n$ such that $\phi(n) + \tau(n) > n$.  I'm not sure how to deal with such abstract functions... help?


I need help solvinf this task, if anyone had a similar problrm it would help me. The task is: Calculate : $\sum_{i=0}^ni^2{n\choose i}  $ I tried this: $ \sum_{i=0}^ni^2{n\choose i}\\ \sum_{i=0}^ni^2\frac{n!}{i!(n-i)!}\\ \sum_{i=0}^ni\frac{n!}{(i-1)!(n-i)!}\\ n!\sum_{i=0}^ni\frac{1}{(i-1)!(n-i)!}\\ \frac{n!}{(n-1)!}\sum_{i=0}^ni\frac{(n-1)!}{(i-1)!(n-i)!}\\ n\sum_{i=0}^ni{n-1\choose i-1}  $ And now, i have no idea how to get solution $2^{n-2}n(n+1)   $ Thanks in advance !

Lets define formula: $$f(n)=\sum_{i=0}^n i^2 \binom{n}{i}$$  What would be genral formula of that?  I first went to discover $$f(n)=\sum_{i=0}^n \binom{n}{i}=2^n$$ (cardinality of power set), and $$f(n)=\sum_{i=0}^n i^2=\frac{2n^3+3n^2+n}{6}$$ then multiplied those together, realising that I am way off.  Then I tried to deduce general presentation of $f(n)$, finding difference of $f(1),f(2),f(3)\cdots$, differences of differences, etc etc, trying to figure what degree of polynomial can represent it, however even after $100$ iterations difference of difference of difference do not converge to some constant, so figuring out polynomial is not working (seems to be that its not polynomial then but some form of $c^n$ function, where $c$ is constant and $n$ is argument of function).  Any idea?


I thought the following rule was set in stone: don't use 'and' between a pair of adjectives preceding a noun:  However, someone in the comments on the following question disagrees, saying: it's not a hard rule, it's a matter of style, and here are some examples to back it up.  I thought to get confirmation and a second opinion.  EDIT 1 It can probably be generalized to a list   EDIT 2 Thanks for confirming what @Lambie said. I have to admit that It involves a technological, theoretical challenge didn't sound so good, or at least It involves a technological and theoretical challenge sounded better (in the first place). Moreover, the link that I supplied does say in the beginning that there are exceptions such as a black and white shirt.  EDIT 3 Regarding the suggested link  It suggests a test for coordinate adjectives. First, the test of replacing the comma with an 'and' doesn't clearly say (like @Anton confirmed) that it's a correct option that can be used (until @Lambie corrected me, I thought you can't use 'and' at all). In both cases, it says you shouldn't. Moreover, according to the test, both of my examples  It involves a technological and theoretical challenge. He wore a black and white shirt.  fulfill the coordinate adjective test, and the link says that comma should be used instead of 'and'. I believe this to be incorrect. If I had to guess, I think the rule might be related to the order of adjectives:  If the adjectives belong to the same category, then they would naturally pass the coordinate adjective test. However, since they belong to the same category, 'and' should be used instead of a comma. At least I think it applies to my two examples above. A link on the subject that might be useful:

I'm writing something and there are several places where I need to use multiple adjectives.  I've always learnt that multiple adjectives should always be separated by a comma, but my supervisor said that they should only be separated by a comma if they are different.  So whereas I would say:     We present a novel, industry-inspired problem [...]   He argues it should be:     We present a novel industry-inspired problem [...]   What is the complete rule regarding multiple adjectives and commas? Thank you.


I am trying to gain some intuition about retracts, deformation retracts and strong deformation retracts (see  for definitions). We have that any strong deformation retract is a deformation retract and any deformation retract is a retract (of course, by definition). Also, it is easy to think in a retract which is not a deformation retract.  Which are some examples of deformation retracts which are not strong deformation retracts?

The question  asks for examples of deformation retracts which are not strong deformation retracts. A comment is given refering the asker to Exercise 0.6 in Hatcher. (The description of this space also appears in , which is about this very same exercise.)  This space, however, seems to be constructed specifically for this purpose.     Are there any naturally occurring (by which I mean not constructed specifically for this purpose, arising in some other way) spaces that are deformation retracts but not strong deformation retracts?   The main reason for asking is that it doesn't seem very likely to me that one would stumble upon such a space at random, so I don't know what to watch out for. One can never be too careful.


I have an object with a number of private properties. It has an empty constructor, and a constructor that accepts an instantiated version of itself. I need to assign this new instance to a deep copy of the old instance. Can this be done? Example:  public class Foo {     private Property p;      public Foo()     {         p = new Property("this and that");     }         public Foo(Foo f)     {         this.Object = f.DeepCopy;   // What would this statement be?     } }   Halp.

I want to do something like:  MyObject myObj = GetMyObj(); // Create and fill a new object MyObject newObj = myObj.Clone();   And then make changes to the new object that are not reflected in the original object.  I don't often need this functionality, so when it's been necessary, I've resorted to creating a new object and then copying each property individually, but it always leaves me with the feeling that there is a better or more elegant way of handling the situation.  How can I clone or deep copy an object so that the cloned object can be modified without any changes being reflected in the original object?


I'm trying to create a warped space curve like examples here. Any ideas? I can't seem to get my plane to dip.

I want to create a animation like those "spacetime deformation" ones, but I am stuck on creating "spacetime".  (a mesh/plane).  I created a plane, gave it a soft body, collisions, and a passive rigidbody.    A cube with a rigidbody and collisions will land and deform the mesh, but it snaps right back.  How can I make it so the cube lands, and then leaves the plane deformed, and the cube just sits there?  I googled around and searched this site, nothing comes up.  An image of what I want (after it settles):    The ball depressed the mesh, creating an indentation.


What is the most efficient way to write the old-school:  StringBuilder sb = new StringBuilder(); if (strings.Count > 0) {     foreach (string s in strings)     {         sb.Append(s + ", ");     }     sb.Remove(sb.Length - 2, 2); } return sb.ToString();   ...in LINQ?

I have the following string array:  var sa = new string[] {"yabba","dabba","doo"};   I can convert it to "yabba, dabba, doo" it using string.Join() but what is the super-cool LINQ way of doing it?  The Join extension method seems promising but for a novice like me very confusing.


I have a python bottle app being served by nginx and uwsgi.  After running for a very few hours, I start getting a 500 error from the web app, and in /var/log/messages I see:  uwsgi: OSError: [Errno 24] Too many open files   lsof for the failing process shows 1023 files open  I've added fs.file-max=200000 to /etc/sysctl.conf  I've added to /etc/security/limit.conf:  uwsgi    soft  nofile 10000 uwsgi    hard  nofile 30000   I've done sysctl -p, and I've rebooted the machine. I still get the app failing when it hits 1,024 file descriptors.  Am I missing some uwsgi configuration, or something else? I can't seem to convince CentOS to give my app more files.

I have successfully increased the nofile and nproc value for the local users, but I couldn't find a proper solution for the processes launched by systemd. Adding max_open_files to the MariaDB configuration doesn't help. su - mysql to change the limit manually doesn't work either (This account is currently not available).  /etc/security/limits.conf  * soft nofile 102400 * hard nofile 102400 * soft nproc 10240 * hard nproc 10240   /etc/security/limits.d/20-nproc.conf (no other files present in the directory)  * soft nofile 102400 * hard nofile 102400 * soft nproc 10240 * hard nproc 10240   /etc/sysctl.conf  fs.file-max = 2097152   /etc/pam.d/system-auth  #%PAM-1.0 # This file is auto-generated. # User changes will be destroyed the next time authconfig is run. auth        required      pam_env.so auth        sufficient    pam_unix.so nullok try_first_pass auth        requisite     pam_succeed_if.so uid >= 1000 quiet_success auth        required      pam_deny.so  account     required      pam_unix.so account     sufficient    pam_localuser.so account     sufficient    pam_succeed_if.so uid < 1000 quiet account     required      pam_permit.so  password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type= password    sufficient    pam_unix.so sha512 shadow nullok try_first_pass use_authtok password    required      pam_deny.so  session     optional      pam_keyinit.so revoke session     required      pam_limits.so -session     optional      pam_systemd.so session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid session     required      pam_unix.so   /etc/pam.d/systemd-user  #%PAM-1.0  # Used by systemd when launching systemd user instances.  account include system-auth session include system-auth auth required pam_deny.so password required pam_deny.so   /var/log/mariadb/mariadb.log  [Warning] Changed limits: max_open_files: 1024  max_connections: 32  table_cache: 491   /proc/mysql_pid/limits  Limit                     Soft Limit           Hard Limit           Units Max cpu time              unlimited            unlimited            seconds Max file size             unlimited            unlimited            bytes Max data size             unlimited            unlimited            bytes Max stack size            8388608              unlimited            bytes Max core file size        0                    unlimited            bytes Max resident set          unlimited            unlimited            bytes Max processes             30216                30216                processes Max open files            1024                 4096                 files Max locked memory         65536                65536                bytes Max address space         unlimited            unlimited            bytes Max file locks            unlimited            unlimited            locks Max pending signals       30216                30216                signals Max msgqueue size         819200               819200               bytes Max nice priority         0                    0 Max realtime priority     0                    0 Max realtime timeout      unlimited            unlimited            us   It is interesting that different processes (users) have different Max open files number:  mysql - 1024 4096 apache - 1024 4096 postfix - 4096 4096


$$\lim_{x \to 0}\frac{1-(\cos{x})^{\sin{x}}}{x^3}$$ So what I have tried is defining three functions, $f(x)=\cos{x}, g(x) = \sin{x}, h(x) = x^3$ What I did next was do Maclaurin expansion for three functions up until the third order: $f(x) = 1 - \frac{x^2}{2} + o(x^3)$ $g(x) = x - \frac{x^3}{3} + o(x^3)$ $h(x) = x^3 + o(x^3)$ So when I plug in these values I get: $$\lim_{x \to 0}\frac{1-(1-\frac{x^2}{2}+o(x^3))^{x-\frac{x^3}{3} + o(x^3)}}{x^3}$$ So after plugging in $x=0$ I get $\frac{0}{0}$ and when I try to apply L'Hôpital's rule I find myself in a situation where I need to calculate the derivative of the denominator several times (which would take too long). I'm positive that I'm correct until this point (I checked on wolframalpha, the result is 1/2). Does anyone know how to proceed from here? Do I need to calculate the derivative of the denominator several times or is there a smarter way?

I need to evaluate the following limit using l'Hospital's rule: $$\lim_{x\to 0}\dfrac{1-(\cos x)^{\sin x}}{x^3}$$  By doing one step, i get $$\lim_{x\to 0}\dfrac{-(\cos x)^{\sin x}[(\cos x) \ln(\cos x)-\frac{(\sin^2 x)}{\cos x}]}{3x^2}$$  If I did this correctly, I still need to use l'Hospital's rule again, but this seems too complicated for an exam question. Is there another, simpler way of doing this, but by still using L'Hospital's.


What would be the solution of : $$\left(\frac{dy}{dx}\right)^2-x\frac{dy}{dx}+y=0$$ I need the working as well, please.

I am so confused,  how to get a solution of following differential equation:  $$(y')^2 -xy' + y = 0$$  My Thought:  Try solving $y'$ to get $y' = \dfrac{ x \pm \sqrt{x^2 - 4y}}{2}$ and now its unsolvable. Kindly help, appreciated.


By default, accounts are shared across multiple stack exchange communities.  Is it possible to disconnect an existing account on one community from the others, without throwing away the rep already gained?

I looked at similar questions and wanted to post a more specific one.  If I wanted one of my accounts on the network to no longer be associated to my global account, could an administrator do it manually? I mean, even if they could, would they?  It's a matter of professionalism. I don't want one of my accounts on the network to be visible from my other accounts. I just want that to be under a separate email that's not one of the OpenIDs associated with my global account.  I realize this would have been easier to do when I joined that site, but it's too late now, and only now have I realized that I don't really want that account showing up.  So can it be done by an administrator? I don't want to wait weeks and weeks for a response by using the contact form (funny, I've waited two with this post)...


For people with Close Vote privilege, when choose flag, the option to mark duplicate repeats 2 times and both points to same window. First one is in the main menu.  The second one is in the Should be closed menu  And both points to

We've changed the flagging format from today(AFAIK) as below,        looks good.  But, when I select it should be closed for another reason...  I can see the same reason duplicate on the top.        What is the need of placing that reason over there? It should not be there. Please remove the dupe.


Here's a screenshot showcasing my problem:     I found  on this issue, but for some reason, it's not working for me. I'm using the Inset tool, and setting the depth to a negative number.  Do I need edge loops first for that to work? There's no way for blender to create vertices at the right spot automatically?

As the title says, how can I make this shape without resorting to a Boolean operation?    This is obviously a very simple example, but I find myself needing to do something like this relatively often when modelling.  Despite using Blender for a couple of years, and considering myself an intermediate to possibly advanced user, I still know of no easy way to make this kind of indentation in an object.  Obviously, if you are looking to make an indentation in the middle of the surface, you can simply select a face and extrude down. As you will know, this does not work at the edge of the surface.  I can create this shape using loop cuts, deleting the faces and then using snap to edge to extrude the edges down to the same level (and then filling in the faces), but it feels cumbersome and a lot of work for what feels like it should be very simple.


May I speak English in the chat related to a localized site? For example, may I speak English in Stack Overflow in Russian chat? And is there any rule about it? P.S. I guess I may because a chat is not a part of a particular site.

Is there any restriction as to what languages are allowed in SE chat rooms? I have seen many people speak in German, Russian or French in the  chat room, but whenever I speak in Persian (to a friend who understands me), some people start nagging that I should only speak in English! In a recent case, one of my chat messages was removed by a moderator because somebody flagged it as non-English! Is there really any rule that restricts the spoken languages in chat rooms? If not, based on what rule was my message removed by a moderator?


When viewing posts by recently active, the last action can generally be linked to directly by clicking the "answered/modified" link. For example, the "answered 5 hours ago" text circled here:    Clicking this takes you to the link https://meta.stackexchange.com/questions/312850/the-second-draft-of-our-code-of-conduct-is-available-for-feedback-and-review/?lastactivity  It seems, however, when that /?lastactivity (either answered or modified) occurs somewhere other than the first page of answers, linking directly to the post fails and, instead, links to the question itself. This makes finding the recent activity difficult, particularly when there are many pages of answers. Yes, I can sort the answers by active but not everyone realizes that's an option.  I've reproduced this on , so it's not an MSE-specific issue nor is it apparently related to the responsive layout. I've also seen this behavior on answers that were answered, edited, or deleted.    To reproduce:   Find a question on the Home or Questions/Active page with >30 answers. Click on the last activity link next to the username of the person who performed that action   Using PPCG questions with >60 answers that are newly answered is the most likely to consistently be a good choice as new answers to questions with many existing answers are unlikely to have surfaced above the latter page/s.  See that the end result is identical to loading the question link/does not take you to the answer.   I suppose that it's possible there isn't a way to fix this but, if there is, it'd be nice to have.

As I pointed out in , the URL scheme for full-form links to answers has changed from:  https://site/questions/question-id/question-title/answer-id#answer-id   to:  https://site/questions/question-id/question-title#answer-id   Pretty much every link that redirects to an answer, including short-form links to answers (i.e. https://site/a/answer-id) and ?lastactivity links to questions, for example, now redirect to the latter form of URL, instead of the former one. (Interestingly, the responses tab in one's own user profile still consists of hard links to the old form.)  Why was this change made? It seems to have , as those are still looking for the old form of URL. Additionally, as per Tim Stone's comment, it also seems to have .  As a test for the above, I tried manually changing the URL to the old form, and it properly oneboxed in chat and properly changed the page and scrolled down.  It also briefly affected SmokeDetector (a community project that widely affects SE sites), until I filed an issue with them and had it fixed.  Was it done because search engines were showing multiple results, since it wasn't clear to them that they were looking at the same page since the URLs to answers were technically different?


I have an application server which we start by running this below command and as soon as we run the below commnad, it will start my application server  /opt/data/bin/test_start_stop.sh start   And to stop my application server, we do it like this -   /opt/data/bin/test_start_stop.sh stop   So as soon as my application server is running and if I do ps aux, this is what I get -   user@machineA:/home/user$ ps aux | grep gld_http user 20426  0.0  0.0   8114   912 pts/4    S+   13:33   0:00 grep gld_http user 40509  0.1  0.9 3878120 1263552 ?     Sl   Sep22   1:53 /opt/data/bin/gld_http   Now I am trying to make a shell script in which I need to stop my application server and then I will check whether my process is running after stopping the server or not, if my process is still running, then I need to do kill -9 of my application pid. And I am not sure how to get the pid of my process in the shell script and then kill it.  Below is my shell script which I have as of now which will shut down my app server and then check whether my process is still running or not and if by any chance it is still running, then I need to get the pid of my process and do kill -9 on that pid.  #!/bin/bash  /opt/data/bin/test_start_stop.sh stop  if ps aux | grep -v "grep" | grep "gld_http" then     echo "Server is still running"     # now get the pid of my gld_http process and invoke kill -9 on it else    echo "Server is stopped" fi   How can I get the pid of my process and do kill -9 on it in my above shell script?  UPDATE:-  So my final script will look like this -   #!/bin/bash  /opt/data/bin/test_start_stop.sh stop  if ps aux | grep -v "grep" | grep "gld_http" then     echo "Server is still running"      # Getting the PID of the process     PID=`pgrep gld_http`      # Number of seconds to wait before using "kill -9"     WAIT_SECONDS=10      # Counter to keep count of how many seconds have passed     count=0      while kill $PID > /dev/null     do         # Wait for one second         sleep 1         # Increment the second counter         ((count++))          # Has the process been killed? If so, exit the loop.         if ! ps -p $PID > /dev/null ; then             break         fi          # Have we exceeded $WAIT_SECONDS? If so, kill the process with "kill -9"         # and exit the loop         if [ $count -gt $WAIT_SECONDS ]; then             kill -9 $PID             break         fi     done     echo "Process has been killed after $count seconds."     else    echo "Server is stopped" fi

When ever I need to kill a background process I do ps -e | grep <process_name>  Which prints something like this 1766 ? 00:00:13 conky , Then I use the process ID to kill it like so kill 1766 .   Is there any way I can simplify this ? Make it quicker ? reduce the amount of typing ?


Here is my code. Can someone help me with this error?  public class ExcahngeSort {      public double[] ExSort(double[] gangnam,int size)     { double temp;          for(int outrloop=1;outrloop<size;outrloop++)         {              for (int innrloop=0;innrloop<size-outrloop;innrloop++)             {                  if(gangnam[innrloop]>gangnam[innrloop+1])                 {                      temp=gangnam[innrloop];                     gangnam[innrloop]=gangnam[innrloop+1];                     gangnam[innrloop+1]=temp;                 }             }         }            return gangnam;     } }   I get an unexpected value [D@360be0printed. I don't know what this means.  Here is my main method:  public class BsortSimulate {     public static void main (String args []){          //BSort bs = new BSort();         ExcahngeSort es = new ExcahngeSort();         double gangnam [] = {12,24};          System.out.println(es.ExSort(gangnam, 2));          } }

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]


So I have this super simple C code: void reverse_string(char* string) {   int length = strlen(string);   for (int i = 0; i < length / 2; i++) {     char temp = string[i];     string[i] = string[length - 1 - i];     string[length - 1 - i] = temp;   } }  int main() {   // char* string = "hey this is a string"; <-- bus error   char string[] = "hey this is a string";   reverse_string(string);    printf("%s\n", string);    return 0; }  and when I use the commented out line I get a bus error, but when I use the line below it everything's fine. Why is that?

The following code receives seg fault on line 2:  char *str = "string"; str[0] = 'z';  // could be also written as *str = 'z' printf("%s\n", str);   While this works perfectly well:  char str[] = "string"; str[0] = 'z'; printf("%s\n", str);   Tested with MSVC and GCC.


Does $\sum_{n=1}^{\infty} \frac{\mu(n)}{n}$ converge and does it converge to $0$ ?. I know that $\sum_{n=1}^{\infty} \frac{\mu(n)}{n^s}$ converges on $Re(s) > 1$ to $\prod_{j=1}^{\infty}{(1-\frac{1}{p_j^{s}})}$ (here of course $p_1, p_2,...$ are the distinct primes)  and taking $s \rightarrow 1^{+}$ suggests $\sum_{n=1}^{\infty} \frac{\mu(n)}{n} = 0$ but this is not rigorous and probably incorrect.

How to prove that Dirichlet series $$\sum _{n=1}^{\infty } \frac{\mu (n)}{n^s}$$ converges to $0$ at $s=1$, where $\mu(n)$ is the Möbius function?   I know it is equal to reciprocal of Riemann zeta function $\frac{1}{\zeta (s)}$ and can be also represented by Euler product $\prod _{n=1}^{\infty } \left(1-p_n^{-s}\right)$, but the product is called divergent if its value goes to 0 and none of its factors is equal to zero, so I think this product will not help me.


I am trying to create a singleton module that can store data.  I want to be able to edit this date only with setters or public functions and only access it with getters.  I was able to create a getter, setter and a set function.  However, I ran into a problem I cant explain when I tried to create a reset function.  I store my default settings in const _defPorts.  I then assign let _myPorts = _defPorts.  (I want to create a private variable _myPorts that is initialised with the constant values from _defPorts.  The problem is when I start setting new values, which I expect will only alter _myPorts, it seems to also change my _defPorts values.  I don't understand what I am doing wrong or how it is possible that my const value is being changed.  Because of this the reset function does not work.  In my console.log I am only displaying the value of _defPorts to show at which point it changes value.  I feel my problem is with the setPorts function but I do not know how to fix it.  Any help or advice would be greatly appreciated! :)  This is the Singleton Module I am trying to create:  'use strict' let activeConfig = (function () {   const _defPorts = {     http: 80,     https: 443,     secure: false   }    let _myPorts = _defPorts    let setPorts = function (value) {     console.log('SP->', _defPorts)     if (value) {       Object.keys(value).forEach((key) => {         if (typeof _myPorts[key] !== 'undefined') {           _myPorts[key] = value[key]         }       })     }   }    return {     setPorts: setPorts,     resetConfig: function () {       console.log('RC->', _defPorts)       _myPorts = _defPorts     },     get instance() {       console.log('GI->', _defPorts)       return this     },     get ports() {       console.log('GP->', _defPorts)       return _myPorts     },     set ports(value) {       return setPorts(value)     }   } })() module.exports = activeConfig   This is the code I am testing it with:  'use strict' const {   ports,   instance: activeConfig } = require('./activeConfig/activeConfig')  console.log('1 ->', activeConfig) console.log('2 ->', activeConfig.ports)  activeConfig   .setPorts({     secure: true,     http: 8080   })  console.log('3 ->', ports)  activeConfig.ports = {   secure: true,   https: 4444 }  console.log('4 ->', ports) console.log('RESET') activeConfig.resetConfig() console.log('5 ->', activeConfig.ports)   This is the console log output:  GP-> { http: 80, https: 443, secure: false } GI-> { http: 80, https: 443, secure: false } 1 -> {   setPorts: [Function: setPorts],   resetConfig: [Function: resetConfig],   instance: [Getter],   ports: [Getter/Setter] } GP-> { http: 80, https: 443, secure: false } 2 -> { http: 80, https: 443, secure: false } SP-> { http: 80, https: 443, secure: false } 3 -> { http: 8080, https: 443, secure: true } SP-> { http: 8080, https: 443, secure: true } 4 -> { http: 8080, https: 4444, secure: true } RESET RC-> { http: 8080, https: 4444, secure: true } GP-> { http: 8080, https: 4444, secure: true } 5 -> { http: 8080, https: 4444, secure: true }

I have an object x. I'd like to copy it as object y, such that changes to y do not modify x. I realized that copying objects derived from built-in JavaScript objects will result in extra, unwanted properties. This isn't a problem, since I'm copying one of my own literal-constructed objects.  How do I correctly clone a JavaScript object?


I am still newbie to ubuntu.  I have a partition (ext4) with all my Documents and Photos, etc. This partition doesn't have any mount point. I want to use Document folder from this partition as my Document folder in Home directory.  I see few possibilities, somehow to mount this partition on booting (and not when I click on it in Folder Manager) and create symbol link from my /home/Documents to /media/partition/Documents or just mount all partition as /home/Document.  It seems like the first solution is cleaner, however the problem is I don't really understand how to mount partition on booting to constant media folder.   What's is the right way to do so?

I have my musics in another partition of the HD, and I would like that, on login, the partition to be auto-mounted, so I can just open the media player and listen to my music. Is there a way?


I lost my root/super user password on Ubuntu server. I tried to boot in a recovery mode and select option drop to root shell.  But it is always asks for:  Give root password for maintenance (or type Control-D to continue)   and I don't remember it.

I need to reset my password. I have followed these steps:    However, then I go to "root" or "netroot" recovery options, it tells me:  Give root password for maintenance (or type Control-D to continue)   Clearly, I do not know the root password. If I type CTRL+D, I return to the list of options. From  I read:  Under chapter 'The Other Way':  4. Highlight the line that begins kernel and press 'e' to edit`   But in the grub configuration file I have no line that starts with kernel. Only:  setparams 'Ubuntu...' recordfail set gxfpayload... insmod part_msdos insmod ext2 set root=... search --no-floppy... linux /boot/vmlinuz-2.6.38... initrd /boot/initrd.img-2.6....   Those are all lines in my GRUB. Which line should I edit? Or is there another way to reset my password?


I need to make two objects on the same scene. The first object should have a sky reflections but the second should not. Is there a simple way to exclude sky reflections from one material but keep it for another? I use Cycles.

In a Cycles scene I have an equirectangular image serving as an Environment Texture background (set in the World settings).  I have a glossy object being partially lit by the Environment Texture, as well as getting reflections from it.  Is there a way I can exclude the Environment Texture from affecting the glossy object completely? I want the image as background wallpaper only. The glossy object should be affected by other objects and lights within the scene: everything except the Environment Texture.


I think is is a simple problem. What i did is to create a button 'remove' in JS when I click an a button 'add' and append it to a existing div.  This works well. BUT for the new created button 'remove' I want to fire a new event - the remove event. This didn't work. What is the problem here?    $(document).ready(function() {    $('#mybutton').on('click', function() {     $('#dateTimeSelector').append('<button type="button" class="btn btn-link removedate" rel="contents" title="Termin entfernen">remove</button>');   });    $('.removedate').on('click', function() {     console.log('remove #dateTimeBox_' + $(this).data());   }); });  <button id="mybutton">   add </button>

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'm a photography enthusiast and I'm looking to buy a canon 4000d and a lens for it, but am not sure whether it's compatible with a canon 4000d or not.

I have a canon 760D. It has a EF-S lens mount. Am I able to use a EF lens with my camera?


If the mass of A is greater of the two, and if air resistance is the same on both, which ball will reach the ground first/simultaneously?  I thought that since the acceleration acting on them is same, both will reach the ground simultaneously. But the answer in the book says that ball A (the one having greater mass) will reach first. I mean, isn't this what people thought before (I guess it's true) Galileo performed his experiment, until they were proven wrong?!

This is a very well known problem, but I can't find an answer in the specific case I'm looking for.  Let's consider two balls :   Ball 1 weighs 10 kg Ball 2 weighs 1 kg Balls have identical volumes (so Ball 1 is much more dense) Balls have identical shapes (perfect spheres)   Let's drop them from a rather important height, on earth, WITH air. (That's the important thing, because all the proofs that I browse take place in a vaccum).  I am arguing with a colleague. He thinks that ball 1 will fall faster in air, and that the two balls will fall at the same speed in a vacuum. I think that the identical shapes and volumes make air friction identical too and that the vaccum has no importance here. Could someone tell who's right and provide a small proof?


I intended to select objects with "Selection group" tool, so in order to achieve that:   pressed B hotkey with Alt or Ctrl or Shift button; moved mouse to form rectangular area.   As a result it removed everything what was outside of rectangular area, forming infinite rectangular pyramid with it's tip on the position of my viewport when I was looking from when making selection. I can rotate around that pyramid now, where only objects (their parts) fitting that rectangular area are visible.  How can I cancel it to see all my objects back? Esc doesn't work.

When looking at my objects in 3d view I'm seeing a gray cone that seems to be hiding other objects.   Can anyone help me turn this off and explain what it is please.  Screenshots attached.


I want to know how can I write in on screen in Ubuntu with screen recording also and voice recording also

I want to be able to reliably record videos for a YouTube channel, however the software I've tried all has individual flaws. The programs I've tried are:   SimpleScreenRecorder (flaw being that the audio begins to echo after a while when recording) Kazam (flaw being the computer crashing whilst processing very long recordings) OBS (flaw being spontaneous freezing of whole computer system) RecordMyDesktop (flaw being that I have 2 monitors so its difficult to get the recording space right)   Are there any reliable alternatives?


Very often you see different forms of "pseudo-tagging" in titles. For example:  c# - how to sniff packets in an app without relying on WinPCap? JS / Jquery: Unable to access the properties of an object returned from an ajax call C++: Using enum as template type argument ...  Some times these can be removed from the title without making the title look weird or non-descriptive. Some other times it's not as obvious:  "MySQL implications of ‘like’ vs ‘join’ query" vs "Implications of ‘like’ vs ‘join’ query" "Can I create a “view” on a Python list?" vs "Can I create a “view” on a list?"    When should the title contain the language it's referring to versus having it on the tags only?

I've seen questions edited to remove the language name from the title. Won't search engines - and folks using search engines - have an easier time finding them if these "tags" are kept as part of the title?


this class is a test to see if my 2 methods (the "endfinder"s) are working (unfortunately they are not). endfinder() is meant to return the index of the next non space character in the provided string; endfinder2() is meant to return the endpoint of the word starting with the index found by endfinder. They're meant to be used to pull out words from a string with multiple words separated by spaces. I've gone over it for a few hours and there must be some obvious answer but I feel like I'm slowly going insane.   I've removed all of the outputs I used to test the code in many attempts to figure out what was wrong to make it cleaner.   Basically, what I've found is that endfinder() always returns 0 for some reason and endfinder2() runs until it reaches the break (I assume that's what happens as it used to loop infinitely before I added it in).  The result I want is start = 3, end = 6  which would make it output "[one]".  The result I get:   [   one  two three] start = 0, end = 17.  Here's my code:  import java.io.*; import java.util.*;  public class test {      static String answer, container;     static int start = 0, end = 1;        public static int endfinder(String perspective) {         int holder = start;         while (perspective.substring(holder, (holder + 1)) == " ") {             holder++;             if (holder == perspective.length())                 break;         }         return holder;     }      public static int endfinder2(String perspective) {         int holder = end;         while (perspective.substring(holder, (holder + 1)) != " ") {                 holder++;             if (holder == perspective.length())                 break;         }         return holder;     }      public static void main(String Args[]) {         System.out.println();         System.out.println();         container = "   one  two three";         start = endfinder(container);         end = start + 1;         end = endfinder2(container);         System.out.println("[" + container.substring(start, end) + "]");         System.out.println();         System.out.println("start: [" + start + "] end: [" + end + "]");         System.out.println();     }  }

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


I have a predictor variable that has many zeros.  The predictor variable is simply a count of the occurrences of some behavior.  The zeros are qualitatively meaningful.  I'd like to use a log transformation of the variable but am unsure what to do with the zeros - again - because they are qualitatively meaningful.  I'd rather not simply add 1 to the variable before logging it.   I've seen others allude to some example from Hosmer and Lemeshow where they use a dummy variable to indicate if a person smokes or not and a continuous variable accounting for the number of cigarettes smoked.  I'm not sure exactly how this coding would work. Does the dummy need to be coded as 1 to indicate zero values of the other continuous variable or should 1 indicate positive values?  I'd also like to log transform the continuous variable because I've got serious over dispersion.  I'm guessing I'd log transform the positive values and just keep the zeros as zeros but some of those zeros are going to be 'true' zeros and others are going to be zeros only because they were '1' on the original scale.    I looked through the applied logistic regression text and I'm not seeing the example that others have alluded to.    Thanks for your input.

When transforming variables, do you have to use all of the same transformation? For example, can I pick and choose differently transformed variables, as in:   Let, $x_1,x_2,x_3$ be age, length of employment, length of residence, and income.  Y = B1*sqrt(x1) + B2*-1/(x2) + B3*log(x3)   Or, must you be consistent with your transforms and use all of the same? As in:   Y = B1*log(x1) + B2*log(x2) + B3*log(x3)    My understanding is that the goal of transformation is to address the problem of normality. Looking at histograms of each variable we can see that they present very different distributions, which would lead me to believe that the transformations required are different on a variable by variable basis.   ## R Code df <- read.spss(file="http://www.bertelsen.ca/R/logistic-regression.sav",                  use.value.labels=T, to.data.frame=T) hist(df[1:7])      Lastly, how valid is it to transform variables using $\log(x_n + 1)$ where $x_n$ has $0$ values? Does this transform need to be consistent across all variables or is it used adhoc even for those variables which do not include $0$'s?  ## R Code  plot(df[1:7])


I have a photo in 72DPI w70 h50 but the printing company tells me i ned a higher DPI. So what happens with the quality if I double the DPI to 144DPI but keep the size w70 h50?

(This question is meant to be a resource to direct others to given that this is a common question.)  Given the task of creating an image that will be printed at a certain size, what pixel dimensions and resolution should I be setting my file at?


I want to say that:  There exists a subset $X$ of $\mathbb{N}$ for which $|X|$ $= 5$.  Can someone explain to me why one would choice either of these three forms over the other ones?   ($\exists$$X$)(($X \subseteq$ $\mathbb{N}$)($|X| = 5$))   "There exists a $X$ such that $X$ is a subset of the natural numbers such that its cardinality is equal to 5."   ($\exists$$X$)(($X \subseteq$ $\mathbb{N}$) $\implies$ ($|X| = 5$))   "There exists a $X$ such that $X$ is a subset of the natural numbers implies that its cardinality is equal to 5."   ($\exists$$X$)(($X \subseteq$ $\mathbb{N}$) $\land$ ($|X| = 5$))   "There exists a $X$ such that $X$ is a subset of the natural numbers and that its cardinality is equal to 5."

I want to represent the statement "Some numbers are not real " using quantifiers. I have been told by my teacher that the correct way to represent this is  num(x)  : x is a number  real(x) : x is real     ∃x (num(x) ^ ¬real(x))    This made sense, i can translate this statement into "There exist some x such that x is a number and x is not real.  But the answer i came up by myself is this one     ∃x (num(x)=> ¬real(x))   In translation , There exist some x such that if x is a number then x is not real.   I just can't get around why my answer is wrong, for some x ; if x is a number then x is not real. Doesn't that sound very similar to the statement "Some numbers are not real".  In one of the video lectures i saw  this  example which made me even more confused.   "No dog is intelligent"   dog(x) : x is a dog  intel(x) : x is intelligent  The representation was      ∀x (dog(x) ==> ¬intel(x))   if this representation is true, how is my representation of "Some numbers are not real" wrong.   PS : I am just a beginner at Discrete math finding my way, please pardon me if the question doesn't meet the quality standards of the community.


I have just gotten a non-name brand android table running 4.0.4 and the model number is A13-MID.  Curious as to if this non-brand tablet would be able to have the new ubuntu touch os that just came out?  and if so then would I just follow the basic instructions that has been up on the ubuntu website? I'm afraid since it's not a Nexus phone or tablet then I won't be able to do it.

With the announcement of the Ubuntu Phone OS I'd like to know what phone (and tablet) models are supported at this time.  Note from foss & Oli: We are making this the master question for all future "Will this work on <insert random tablet/phone/device here>?!" questions


I guess the title says it all. I know I can get help on a specific command, for example wget, like this:  wget --help   But how can I get help on some specific option of that command? For example, I might want to find out about (and only about) wget's -A option. You won't believe it, but an hour of googleing didn't help me on this question :)  Thanks a lot in advance!

Is there a option to search within manpages?


The edge loops do not go on the inside of the cube wall. I made the wall from a cube following a floor plan. I tried using the knife tool but the edges it generated were not able to be selected. What is a solution to this. The walls all have 4 vertices and are not n-gons. Thanks Blend File:

I have pressed CTRL + R to create a loop cut which is interrupted at the left side of the front wall. I am not sure why my loop cut stops instead of going all the way round.    I have uploaded a ~.blend file here:   Thank you!


In App Store app, if I search for a word.  What does the returned listing order of apps base on?  Let's say, it returned app1, app2, app3, ..., app10.  What was the listing order based upon?

I have an iOS application - an alarm clock. I released it a little over a month ago. Initially it was paid, but when I saw there were virtually no purchases (from 0 to 4 a day), I changed it to be free for a period of time. When it become free, in less than 10 days it has been downloaded more than 30,000 times, and more importantly (I think) it moved much higher in the search results when the user searches "alarm" - it reached 20th place in the results. During that time I also received very good reviews in the AppStore. But today I changed it back to paid, and now when I search "alarm" my app is shown at the bottom of the 4TH PAGE. Given that one page contains 120 apps, this is very bad for me and I don't understand why this happened. Can anyone tell me how does AppStore ranks search results and is there a way to move my app higher in the rankings, please? :) Huge thanks!


I need to learn about a paradigm totally new to me. I don't have enough experience to formulate specific questions yet. The area is one which has undergone significant change over the years.  Web searches return info on mostly abandoned approaches, and published books on the subject are outdated, which, as a novice in the area, I don't discover until I've wasted time exploring the abandoned approach or wasted time and money on the outdated book(s). Is there a way to ask for pointers to online "Getting Started" resources that won't immediately get shut down as off-topic?

Questions like looking for css templates, blog templates, icons ... In general, resources (let's leave the licensing terms aside for now) which you might need when building a project of your own. Where should those questions go?  They're definitely not on-topic on Stack', SuperUser maybe although I doubt it. Webapps? Hmm, probably not.  Is there a place where they would be on-topic on the SE network?


Has anyone figured out a way to toggle the function keys on and off via key board shortcut on a macbook? Even remap the fn key to work more like the caps lock where you do not need to hold it down. It would be really nice to just remap the caps lock to toggle function keys, instead of using it for capitalizing.

Is there a keyboard shortcut for toggling between Function and classic F keys?


Does C# allow hashtables to be populated in one-line expressions? I am thinking of something equivalent to the below Python:  mydict = {"a": 23, "b": 45, "c": 67, "d": 89}   In other words, is there an alternative to setting each key-value pair in a separate expression?

I want to use a collection initializer for the next bit of code:  public Dictionary<int, string> GetNames() {     Dictionary<int, string> names = new Dictionary<int, string>();     names.Add(1, "Adam");     names.Add(2, "Bart");     names.Add(3, "Charlie");     return names; }   So typically it should be something like:  return new Dictionary<int, string> {     1, "Adam",    2, "Bart"    ...   But what is the correct syntax for this?


I want to create a new command to do a certain diagram using tikz. The code looks like this:  \documentclass[12pt]{article} \usepackage{tikz} \usetikzlibrary{matrix} \newcommand{\D}[4]{ \begin{tikzpicture}   \matrix (m) [matrix of math nodes,row sep=1.5em,column     sep=1.5em,minimum width=2em]           {             &#1&\\             #2& &#3\\             &#4&\\};            \path[thick]            (m-1-2) edge (m-2-1)            edge (m-2-3)            (m-3-2) edge (m-2-1)            edge (m-2-3); \end{tikzpicture} } \begin{document} \D{a}{b}{c}{d} \end{document}   But I get this message:  ! Undefined control sequence. <argument> \pgf@matrix@last@nextcell@options   l.23 \D{a}{b}{c}{d}   How can I solve it?

For  I wanted to define a shortcut for creating a matrix inside a tikzpicture. As a minimal example, consider  \newcommand\mymatrix[1]{     \begin{tikzpicture}         \matrix[matrix of math nodes] {#1};     \end{tikzpicture}% }   which would then be used as  \mymatrix{     a & b \\     e & f \\ }   But LaTeX complains about Package pgfbasematrix Error: Single ampersand used with wrong catcode at the line with the closing brace of \amatrix{}. Why does it do that and how can I avoid it?


Spectre protection () was released for Kernel 4.9.77 and 4.14.14 by the Linux Kernel team on January 15, 2018. The Ubuntu Kernel team only released  on January 17, 2018 and have not published kernel version 4.14.14. For the Meltdown patches (KPTI->KAISER->KASLR) the Ubuntu Kernel team released the  updates at the same time for 4.9 and 14.14 but the Spectre patch is missing in 4.14:  4.9.74 Jan 2nd 9:10pm ....... 4.14.11 Jan 2nd 10:40pm 4.9.75 Jan 5th 4:20pm ........ 4.14.12 Jan 5th 5:40pm 4.9.76 Jan 10th 10:20am .... 4.14.13 Jan 10th 10:50am 4.9.77 Jan 17th 10:20am .... 4.14.14 Missing  Mainline/Stable Ubuntu Kernel version 4.14.14 is still missing as of Jan 20th 5:46pm. Three days late and counting... I like to test the latest stable kernels and this is even more important now with the Spectre security hole. I've googled for reasons but came up empty handed. Is there a newsletter or something that would explain why? Or is it as simple as someone forgot to push a button? NOTE: Spectre protection is not being provided for LTS Kernels 4.4 and 3.18 by the Linux Kernel team however they have updated sysfs to indicate Spectre vulnerability. So far the only LTS Kernel versions offering Spectre protection are 4.9 and 4.14. Current Release Candidate (experimental kernel) 4.15 will soon have Spectre protection. Ubuntu 18.04 (Bionic Beaver) will be based upon 4.15 in April when it is no longer a Release Candidate and becomes a Mainline/Stable Kernel.  End of Story Thanks to Thomas Ward's help I got in touch with the Ubuntu Kernel Team and Mainline/Stable Ubuntu Kernel version 4.14.14 was published January 20, 2018 at 1:10pm.

Any questions relating to status updates, or asking if anything is going to be patched for these vulnerabilities should be closed as duplicates of this question.    are in the news right now and sound pretty severe. I don't see any security updates from Ubuntu that cover these vulnerabilities.  What is Ubuntu doing about these vulnerabilities, and what should Ubuntu users be doing?  These are CVE-2017-5753, CVE-2017-5715 and CVE-2017-5754.


I have this matrix but I would like the second element in the second row to be highlighted, is that possible? I have tired everything!!! this is what I have so far... \begin{bmatrix} 1 & 2 & 3\\ 2 & 3 & 1\\ 3 & 1 & 2 \end{bmatrix}

I have a matrix and need to highlight some elements in the matrix. I have found how to highlight a single element (I want to put the cell in the square):  $$ A = \begin{bmatrix} \fbox{0} & \fbox{0} & 0 \\  \fbox{0} & \fbox{0} & 0 \\ 1 & 1 & 1 \\  \end{bmatrix}$$   But how can I outline elements of the submatrix like in the picture below? I need just a frame where some elements are located.


Eccentricity is defined in terms of directrix as:$$e = \dfrac{PS}{PM}$$  Also eccentricity has a formula $$e=\dfrac{c}{a}$$ where $c$ is distance between center and focus $a$ is the length of semi major axis. How are these two equivalent? Looks some symmetric triangles are involved, but I don't see them. Any help?

How is $\frac{PF}{PD} = e = \frac{C}{A}$ ? where e is eccentricity, P stands for any point on the ellipse. $F$ stands for one of the foci. $e$ stands for eccentricity. $D$ is a point on the directrix of the ellipse. 'C' is the distance from the center to the focus of the ellipse 'A' is the distance from the center to a vertex.   This is referring to an ellipse/hyperbola/parabola and their conic sections. The problem is not the proof for how $PF/PD = e$, or how $C/A = e$, but how the two equate to each other. (The letters stem from the points/foci of an ellipse of a cone and its directrix).  What is the answer that does NOT use analytic geometry? (only trigonometry)


is my /etc/apt/source.list file. I get many problems in the output of sudo apt-get update:  $ sudo apt-get update [sudo] password for tim:  Err http://cran.cnr.Berkeley.edu precise/ Release.gpg                             Could not connect to cran.cnr.Berkeley.edu:80 (169.229.201.201). - connect (111: Connection refused) Err http://ppa.launchpad.net precise/main Sources           404  Not Found Err http://ppa.launchpad.net precise/main i386 Packages     404  Not Found  W: Failed to fetch http://cran.cnr.Berkeley.edu/bin/linux/ubuntu/precise/Release.gpg  Could not connect to cran.cnr.Berkeley.edu:80 (169.229.201.201). - connect (111: Connection refused)  W: Failed to fetch http://ppa.launchpad.net/venerix/blug/ubuntu/dists/precise/main/source/Sources  404  Not Found  W: Failed to fetch http://ppa.launchpad.net/venerix/blug/ubuntu/dists/precise/main/binary-i386/Packages  404  Not Found  W: Some index files failed to download. They have been ignored, or old ones used instead.   I have several errors at the end of the output. How can I solve the problems?  Thanks!

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?