Assume there is a rocket with 10 kg of fuel in a large empty space without any external forces such as gravity.  Rocket burns 1 kg of fuel and gets a $v_1$ velocity gain. Now it is moving in $v_1$ constant speed.  Then it burns another 1 kg of fuel. If the rocket gains $v_1$ velocity gain this time too, the kinetic energy gain of the rocket is higher this time since the velocity of the rocket is $2v_1$ and kinetic energy is proportional to the square of the velocity.  Since the state of the rocket in both times it burned fuel is the same for an observer inside it (first time it was not moving, and the second time it was moving in constant speed, which is effectively same as not moving, if there is nothing around for a reference), I cannot see any reason why the rocket cannot get the same $v_1$ velocity gain. So it appears that the kinetic energy gain is higher the second time.  So, would the rocket gain a higher kinetic energy the second time?  If the rocket gains a higher kinetic energy at higher speed, let's assume the rocket got accelerated to a very high speed by some external means. Then at this very high constant speed, rocket starts accelerating by its own by burning fuel. The kinetic energy gain may even exceed the total energy contained in the burned fuel. How can this happen?

Consider a rocket in deep space with no external forces. Using the formula for linear kinetic energy $$\text{KE} = mv^2/2$$ we find that adding $100\ \text{m/s}$ while initially travelling at $1000\ \text{m/s}$ will add a great deal more energy to the ship than adding $100 \ \text{m/s}$ while initially at rest: $$(1100^2 - 1000^2) \frac{m}{2} \gg (100^2) \frac{m}{2}.$$ In both cases, the $\Delta v$ is the same, and is dependent on the mass of fuel used, hence the same mass and number of molecules is used in the combustion process to obtain this $\Delta v$. So I'd wager the same quantity of chemical energy is converted to kinetic energy, yet I'm left with this seemingly unexplained $200,000\ \text{J/kg}$ more energy, and I'm clueless as to where it could have come from.


I have an ETL/database server running on a 16.10 system. I get errors when trying to apt install packages so I’d like to upgrade. Is it safe to do so?  It looks like I need to run commands to edit files.   Database has streaming replication and I rsynced all of my files (I hope) to another system.

I am currently using Ubuntu 10.04. I know there is a 10.10 release, but can I upgrade directly to 11.04? Could you walk me through the steps please?


The English verb "there be" in its various forms "there were," "there is," "there are," "there will be," etc. are equivalent to the Spanish verb "haber" in its forms "hubo," "hay," "habrá," etc.  Technically, when used in this way, "there" is an adverb (some say it is a noun or expletive, but I disagree). But "there" is also an adverb with an entirely different meaning and, for at least some native speakers, a different pronunciation when used to designate location: "We went there for our honeymoon."  So is "there be" classified as a phrasal verb of the form "adverb + verb"?  ADDENDUM: Does anyone know when this form arose in English?

What part of speech is there in the sentence “There is a book on the table?”  Also, while typing it out, another question pops up vis-à-vis punctuation. In my complete first sentence above, I ended it with a question mark since my main sentence is a question. The quote is not a question, but it looks like it because of the question mark. Is this the right way to punctuate?


According to known discoveries made till now , we have came across all the charged particles which have the property of mass . So can we assume that there is a correlation between charge and mass and hence can we say that a mass-less can't exist.

Are there any massless (zero invariant mass) particles carrying electric charge?  If not, why not? Do we expect to see any or are they a theoretical impossibility?


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

Find all continuous functions $f:\mathbb R^{+}\to\mathbb R^{+}$ such that $f(x)^2=f(x^2)$ for all positive reals $x$.  If $f$ is a constant function, then $f(x)=1$. If $f$ is non-constant, I'm suspecting the only solutions are of the form $f(x)=x^k$, where $k$ is a constant, but I have no idea how to prove this. Thanks in advance.


I have a new 2019 MacBook Pro 16" on Catalina 10.15.5. I recently got it back from the shop - upper case replacement for bad keyboard that included replacing the battery as part of the repair. Now occasionally when plugged in the battery charge actually decreases. For instance last night I opened it, it was plugged in at 100%. I used it to make an email and print a few pages for 15 minutes and the charge actually decreased to 93%. The icon shows when plugged in. What would cause this? Ideas? Does anyone else have a MBP that decreases the battery charge while plugged?

so I have a 2019 MacBook Pro 16" on Catalina 10.15.5.  I recently got it back from the shop - upper case replacement for bad keyboard that included replacing the battery as part of the repair.  Now I've noticed that while its plugged in and 100% charge and I'm using it, the battery charge actually decreases.  For instance last night I opened it, it was plugged in at 100%. I used it to make an email and print a few pages for 15 minutes and the charge actually decreased to 93%.  The icon shows when plugged in. I have looked at  but Battery Health Management is not turned on so it seems to be something else in my case. How can I diagnose and solve this issue? PS: I'm using an OEM 96W power adapter.


I have a list of datetimes that were imported as strings: datetimes = ['datetime.datetime(2021, 2, 16, 12, 39, 54, 30886)',  'datetime.datetime(2021, 2, 16, 12, 40, 5, 238783)' ... ]  How can I convert the string into a datetime object?

I've got a huge list of date-times like this as strings:  Jun 1 2005  1:33PM Aug 28 1999 12:00AM   I'm going to be shoving these back into proper datetime fields in a database so I need to magic them into real datetime objects.   This is going through Django's ORM so I can't use SQL to do the conversion on insert.


I've heard numerous articles and videos state that when it comes to black holes and singularities our "math breaks down".  Is there any other areas in physics where math similarly "breaks down", where the equation returns zero or unexpected values?

I am assuming there are two constituents that obliterate our current model of physics;   that it's infinitely dense that it's infinitely small   Please correct me if I am wrong.


Trying to copy an 11.3G file to a brand new 65G flash drive. Keep getting error message "the file is too large for the destination file system. It is a brand new flash drive formatted to fat32. On windows7. Any suggestions??  Thanks!

Yes, why can't I?  I was stashing away some old photography backup zips last night. I could copy 4 of my > 1 GB backup zips to my external USB connected hard-drive when I got the error message "Cannot copy file. Not enough free space." (sort of) for a zip of roughly 7 GB.  But there are 120 GB free. Why is this?   EDIT: Clarification - the files that I could copy was smaller than 4 GB. The failing one was 7 GB. The cause seems to be the FAT32 4 GB limit.


It appears that the suggested edit indicator (to users with the “moderator tools” privilege) has disappeared from the new top bar.  The suggested edit indicator is useful. Suggested edit review is not like other review tasks which can wait until somebody's interested in doing moderation. A pending suggested edit on a post locks the post against modifications by users without the edit privilege. Without the indicator, posts will spend longer in that semi-locked state. That's not good.  Please bring back an apparent notification of pending suggested edits.

Though I never quite understood what those numbers were and they were quite ugly, they were the only reason I ever visited the reviews page.   Can we have similar functionality back on the top bar please?


I need to install about 20 tablets powered 24/7 (24 hours, all week). Is there any problem or potencial damage about it?

I usually disconnect my cellphone from the charger some time after it's fully charged because I'm afraid the battery could lose capacity over time if I don't. However, I believe modern electronics should be able to handle this kind of scenario and automatically stop charging the battery once it's full. Does this apply to modern Android phones? Or do I need to continue disconnecting it all the time?


I have a desktop PC with Windows 10 Pro and connect to The Internet via a cable to my router. I have set my connection to "metered" and told Windows Update to NOT download over metered connections. That did nothing as some time ago some update(s) were forced on me postfactum. Meaning Windows had silently and sneakily downloaded them and just told me I need to restart to install them. Again with no option not to do so, I could postpone it, at best but when Windows' patience runs out it would force my computer to restart. So I changed some Group Policies. Policy                                                                                Setting         Winning GPO -------------------------------------------------------------------------------------------------------------------------------------------------- Allow updates to be downloaded automatically over metered connections                                           Disabled        Local Group Policy Always automatically restart at the scheduled time                                                              Disabled        Local Group Policy Configure Automatic Updates                                                                                Disabled        Local Group Policy Do not adjust default option to 'Install Updates and Shut Down' in Shut Down Windows dialog box                 Enabled         Local Group Policy Enabling Windows Update Power Management to automatically wake up the system to install scheduled updates       Disabled        Local Group Policy No auto-restart with logged on users for scheduled automatic updates installations                              Enabled         Local Group Policy Turn on recommended updates via Automatic Updates                                                               Disabled        Local Group Policy Turn on Software Notifications                                                                                Disabled        Local Group Policy  Now even that doesn't help. Again I have a notification a (useless) update was downloaded and I must restart my computer to install it. Is there a way to completely stop Windows 10 Pro from checking for updates?

We've upgraded some machines to Windows 10 and realized there were some updates which updated as required. However, I realized there was no option available to stop the download similar to that on Windows 7 and 8.1. The only way I could stop the download was to stop the Windows Update service.  My question is does anyone know of a way to stop auto updates or is stopping the service is the only solution?


I am using python to parse a JSON file, I know it is because of this ¥,   that I got this error when I was using json.loads  UnicodeDecodeError: 'utf8' codec can't decode byte 0xa5 in position 106: invalid start byte   But how do I get around it? Do I decode and encode again?  ¥ is the Chinese currency sign, but I am not sure which code category it belongs to.  Thanks!  update:  ====================  I think my question should be, If you see this symbol, how do you guess the encoding.  An answer to this question maybe:  If you see ¥, then "utf-8" won't work, try "latin-1" instead.  Is this understanding correct?

I received some text that is encoded, but I don't know what charset was used. Is there a way to determine the encoding of a text file using Python?  deals with C#.


So, today I did my first attempt at home made gummies using 35g of gelatine with 1 cup water and 1/2 cup sugar.  When it cooled though, all I had was really tough jello.  Should I just add more gelatine, or is there another chemical I could use?  I have looked at methylcellulose, carrageenan, agar, cornstarch, and pectin in addition to gelatine, but there doesn't seem to be a good comparison of these on the web.  Additionally, if anyone has insight into special techniques I could use, it would be really helpful.  Thanks

I've been trying a simple recipe I found on the internet, which is a simple recipe consisting mostly of gelatin.  The problem is that the end result is basically just a fruit-flavoured jelly (Jell-O?), rather than the more chewy gummy-bears (Haribo) style of jelly confectionery.  Can anyone suggest what I need to do to make them less springy and more chewy.  It's all difficult to articulate!  Here's what I used for the first test-batch:   12 tbsp sugar 12/3 cup fruit juice 8 tbsp Golden Syrup 8 tbsp gelatin   soften the gelatin in 1/2 cup of cold water. place sugar, syrup and the juice in a pan and gently heat until sugar dissolves. Stir in the gelatin and stir until dissolved. Pour into moulds and wait until set.    Thanks


Which one is right? And WHY? 1 I could see them run towards the shop 2 I could see them running towards the shop

"Heard me [infinitive]" vs. "heard me [present participle]"             At that time, you wouldn't have heard me talk about it.   At that time, you wouldn't have heard me talking about it.         At that time, you wouldn't have heard me condemn it.   At that time, you wouldn't have heard me condemning it.         Which one of the above sentences are incorrect and why?


I am attempting to follow the repository pattern described .   Can someone please shed some light on what this really means, and what the benefits of it are? The      <TEntity> where TEntity : class, IEntity   part of the classes signature  public interface IRepository<TEntity> where TEntity : class, IEntity {     TEntity Get(int id);      int Save(TEntity entity);      void Delete(TEntity entity);         }   I do not see any noticeable effect in my implementation of IRepository:   public class AppUserRepository : Repository, IRepository<AppUser> {     public void Delete(AppUser entity)     {         using ( var context = new SourceEntities())         {             context.AppUsers.Attach(entity);             context.AppUsers.Remove(entity);             context.SaveChanges();         }     }      public AppUser Get(int id)     {         using (var context = new SourceEntities())         {             return context.AppUsers.Where(x => x.Id == id).SingleOrDefault();         }     }      public int Save(AppUser entity)     {         using (var context = new SourceEntities())         {             if ( entity.Id == 0 )             {                 // this is a new record                 context.AppUsers.Add(entity);             }             else             {                 // existing record                 context.AppUsers.Attach(entity);                 context.Entry(entity).State = EntityState.Modified;             }              // save the record             context.SaveChanges();              return entity.Id;         }     } }

I have a VB background and I'm converting to C# for my new job.  I'm also trying to get better at .NET in general.  I've seen the keyword "T" used a lot in samples people post.  What does the "T" mean in C#?  For example:  public class SomeBase<T> where T : SomeBase<T>, new()   What does T do? Why would I want to use it?


So I am trying to make a program that uses linked list. I am getting a runtime error when I try to run it though. I am completely confused and have literally no idea on how to fix this. There is apparently something wrong with my traversal method in MyLinkedList class.  Error:  Exception in thread "main" java.lang.NullPointerException           at MyLinkedList.traversal(MyLinkedList.java:68)           at MyLinkedListClient.main(MyLinkedListClient.java:13)  It highlights this line of code: result = temp.getElement() + "-->";  I apologize if I have asked this in a poorly written manner. My 2nd time using this website so hopefully I do not chewed out too badly >< lol Oh and sorry if my code is formatted weird, it got weird trying to get it to look like code in my post lol.  Any help is greatly appreciated.   public class MyLinkedListClient {  public static void main(String [] args) {    MyLinkedList<String> myList = new MyLinkedList<String>();    myList.addFirst("MSP");   myList.addFirst("RST");   myList.addFirst("LAX");   myList.addFirst("PHL");       System.out.println(myList.traversal());      System.out.println(myList.removeFirst() + " is removed.");    System.out.println(myList.traversal());  }  }//end of class     public class MyLinkedList<E> {  //instance variables private Node<E> head; //private Node<E> tail  private int size;  //constructor public MyLinkedList() { head = null; //do something with tail size = 0; }     public boolean isEmpty() {   if(head == null)      return true;    return false; }  public int size() {   return size; }  public void addFirst (E element) {   Node<E> temp = new Node<E>(element, null);    //do something with tail    if(isEmpty())      temp.setNext(head);   else {      temp.setNext(head);      head = temp;   }   size++; }   public E removeFirst() throws EmptyListException {   if(isEmpty())      throw new EmptyListException("The list is empty.");    Node<E> temp = head; //step 1    head = head.getNext(); //step 2    temp.setNext(null); //step 3    size--;    return temp.getElement(); //step 4 }  public String traversal() {    if(size() == 0)      return "Empty list.";    Node<E> temp = head;    String result = "Head -->";    int i = size();    while (i > 0) {      result = temp.getElement() + "-->";      temp = temp.getNext();      i--;   }    return result; }  /* public boolean search( E element) {  }    */  }//end of class

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?


How do I search on a Stack Exchange for questions without a specific tag, for example questions without the  tag on ?  Edit: Why is this question marked as dubplicate? In this question I asked to search for questions without a specific tag. The question mentioned is "How do I search for questions with specific tags?" ?

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


I have a table like this:  // names +----+-------+ | id |  name | +----+-------+ | 1  | jack  | | 2  |       | +----+-------+   And here is the expected result:  // names +----+-------+ | id |  name | +----+-------+ | 1  | jack  | | 2  | jack  | +----+-------+     And here is my query:  update names set name = ( select name from names where id = 1 ) where id = 2   But it throws:     ERROR 1093 (HY000): You can't specify target table 'names' for update in FROM clause   How can I do that?

I have a table story_category in my database with corrupt entries. The next query returns the corrupt entries:  SELECT *  FROM  story_category  WHERE category_id NOT IN (     SELECT DISTINCT category.id      FROM category INNER JOIN         story_category ON category_id=category.id);   I tried to delete them executing:  DELETE FROM story_category  WHERE category_id NOT IN (     SELECT DISTINCT category.id      FROM category        INNER JOIN story_category ON category_id=category.id);   But I get the next error:      #1093 - You can't specify target table 'story_category' for update in FROM clause    How can I overcome this?


I tried opening them with NotePad++ and it just came out as garbled junk. Is there any way I can edit the .DAT file, for example, to make myself go in creative? I am playing modded minecraft if that makes a difference.

This question is regarding the minecraft Beta 1.8 prerelease -- I have a beautiful house in single player survival which I'd like to record while flying.  I want to be able to change the game mode of my survival map to creative to be able to fly through it without installing a mod. I know it is possible if you run the map on a multiplayer server via the command /gamemode <user> 0|1 but I want to achieve this in single player :)  I think this would be possible through editing your level.dat file as I think that's where the game mode for the map is stored.


It looks like Google's index has been taken over by a man in the middle proxy scheme.  Search Google using google.com/search?q=usinfonow.com and google.com/search?q=stackexchange+usinfonow.com to see some examples.    Programming related queries on Google that would normally show stackoverflow.com pages in the top list of results are now being replaced by the proxy site stackoverflow.usinfonow.com.    How do we prevent this in the future? Any ideas?

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


I'm trying to send an automated e-mail through PHP, that prints some pre-defined variables.  It works as expected if I write the php script directly into the main file (akkoord.php). However, I would like to save the script as a function in a separate php file (email.php), because I want to include it in other php files as well.  I saved the script as email.php, turned it into a function mail() and included email.php in akkoord.php. The function works and it sends an email, but the variables (that I defined in akkoord.php) are not coming through. I figured this would be a scope problem, so I redefined them as global variables in email.php. However, it still doesn't work.   (simplified) Akkoord.php:  <html> <head>  <?php   $naam = $_GET["naam"];   $reisnaam = $_GET["reisnaam"];  ?>  <?php   include'email.php';  [some other code that works fine]  email();  ?>  </head>  <body> [some body] </body>  </html>   And email.php:   global $reisnaam;  function email(){      global $reisnaam;      global $naam;      $to       = 'my_email@email.my';      $subject  = $reisnaam ;      $message  = 'Hello'.$naam;      $headers  = 'From: some@body.nn';      if(mail($to, $subject, $message, $headers))          echo "Mail sent";      else          $fout .= "Not sent";    }  ?>   I checked if email.php is included - it was (after all, it does send the email). Idem for the function email().  Any ideas of where I'm going wrong?   *edit: fixed the ' in $headers

How can I create or use a global variable in a function?  If I create a global variable in one function, how can I use that global variable in another function? Do I need to store the global variable in a local variable of the function which needs its access?


I want to change the date format from what I chose in the Ubuntu installation, and it works by going to Region & Language and selecting the format that I want, but when I log out of the user, the date that is shown in the top of the screen is still the same and hasn't changed. is there anyway to change the date format for there?

I've installed Ubuntu 19.10, language/locale/formats are set in US/en. And everything seems to work OK, except datetime language on login screen (when I turn on my laptop and see fields for user/password logging). It has local-language-style.  So, datetime language for user / lockscreen picks up correctly, but for login screen - nope. What's the reason and how can I fix this ?  Output of locale command:  LANG=en_US.UTF-8 LANGUAGE= LC_CTYPE="en_US.UTF-8" LC_NUMERIC=en_US.UTF-8 LC_TIME=en_US.UTF-8 LC_COLLATE="en_US.UTF-8" LC_MONETARY=en_US.UTF-8 LC_MESSAGES="en_US.UTF-8" LC_PAPER=en_US.UTF-8 LC_NAME=en_US.UTF-8 LC_ADDRESS=en_US.UTF-8 LC_TELEPHONE=en_US.UTF-8 LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=en_US.UTF-8 LC_ALL=


This is the second iteration of  (I have now made a ) I have now added in some of the suggestions given by linksassin such as simplifying it to just one type of rune and adding a material cost. I have not added in limited duration or limited number because it is intended to allow the player to make a consumable similar to spell-scrolls or potions. if they intend to make them during extended downtime then thats fine, its the same as making spell scrolls or buying potions during downtime.  Rune Caster Prerequisites: ability to cast at least one spell of 1st level or higher When you take this feat you can imbue your spells into a rune by casting the spell as a rune, this means that you must have the object you want to put the rune on within reach for the whole duration of the casting as well as any tools required to make the rune. The casting time is also affected. Casting When casting a rune you add 1 hour to the casting time and 20gp per spell level stored on top of the normal components of the spell. Triggers When making a rune you may customise the trigger conditions from the following list:  Touch  Command word spoken  … by [specify creature(s)]  … with [specify body part]   When defining creatures that can activate the rune you may be as specific or general as you want. The DM interpretes the designated creatures as your character would have interpreted them when you made the rune. Ranges When you store a spell in a rune the following rules change the range:  A range of touch becomes a range of self  When a range is listed and a target the person who activates the rune designates the target  When a range is used with an aoe the origin is automatically wherever the rune is.   Activating a rune When a rune is activated the spell is released acting as if it had just been cast without requiring any components. The rune then disappears leaving no trace of its presence. To activate a rune you must complete the trigger, this means speaking any command words and physically touching the rune each if applicable.  I want to know specifically is it to powerful/ not powerful enough and if so what would be a reasonable way of correcting the issue.

Quite simply (and similarly to my other questions about previous versions of this feat  and ) I want to know if this feat is balanced and if not then what should be done to improve it? Since the last iteration I have changed the wording as per David Coffron's answer, increased the time and monetary cost as well as added in the action requirement to activate the rune as per Ruse's answer and increased the costs as per linksassin's answer     Rune Caster      Prerequisites: ability to cast at least one spell of 1st level or higher      When you take this feat you can imbue your spells of 1st level or higher into a rune by casting the spell as a rune, this means that you must have the object you want to put the rune on within reach for the entire duration of the casting as well as any tools required to make the rune.      When casting a rune you add the time listed in the cost time table to the casting time and the cost listed in the cost time table to the components of the spell in accordance with the stored spell.      \begin{array}{|l|l|l|} \hline \text{Spell level} & \text{Time (hrs)} & \text{Cost (GP)}\\ \hline 1 & 1 & 50 \\ \hline 2 & 2 & 100\\ \hline 3 & 4 & 500\\ \hline 4 & 6 & 1,000\\ \hline 5 & 8 & 5,000\\ \hline 6 & 12 & 10,000\\ \hline 7 & 16 & 50,000\\ \hline 8 & 18 & 100,000\\ \hline 9 & 24 & 500,000\\ \hline \end{array}      When making a rune you choose a trigger which is touch and/or command word and can be specified to only a group of people/creatures or a body part. When defining creatures that can activate the rune you may be as specific or general as you want. The DM interprets the designated creatures as your character would have interpreted them when you made the rune.      When you store a spell in a rune some of the ranges are altered, a range of touch becomes a range of self, a range and target keeps the same range and the person who activates the rune designates the target and range with an aoe sets the origin to the center of the rune, lastly a range of self stays the same.      When a rune is activated the spell is released acting as if it had just been cast without requiring any components or concentration. The rune then disappears leaving no trace of its presence. To activate a rune you must complete the trigger, this means speaking any command words and physically touching the rune each if applicable, this requires the activator to use the object interaction action while within reach for touch runes and while within 60 ft for command words. If both triggers are used then they must both be fulfilled within the same turn.


Hello Android Enthusiasts,  I was wondering if KingRoot can potentially brick my HTC One and Nexus 9. I have not rooted either yet for my warranty is still active. If either is bricked, is there a way that it could possibly be recovered? If possible, could you please provide me with some statistics or percentages regarding the likeliness of one of these devices becoming bricked? Here are a few more specifications about my devices:  HTC One M8 Harman Kardon Edition from Sprint  HTC Google Nexus 9 (No carrier, WiFi)  Thank you in advance.  Regards,  Ani

I see lots of tutorials telling me how to root my phone (Motorola Droid), but none of them mention any potential "side effects."  Aside from a few relatively minor issues that seem to require rooting to fix, I'm basically happy with the phone and therefore a little leery of messing with a device that cost me a lot of money and is only a few months old.  Assuming that I'm just talking about rooting, and none of the typical post-root actions (like installing a custom ROM), am I taking any risks by choosing to root?   Does it have the potential to brick the device? Will it void my warranty? Will I stop getting updates? Will the cops show up at my front door the next day? (Yes, I'm being facetious.) Anything else I should be aware of?   (See also: )


Theorem: Suppose there is a sequence of positive real numbers such that $a_{1}a_{2}... a_{n}=1$ then   $$(1+a_{1})(1+a_{2})...(1+a_{n})\geq2^{n}$$  (Prove by induction, do not use geometric mean)  I believe I have a proof, but I am unsure it is correct. Could you help me identify any mistakes or find a more direct approach?  Proof: Let $n=1$ then clearly $a_{1}=1$ and $(1+1)\geq2$  Assume the claim is true for all sequences of length $k<n$. Then from a sequence $a_{1}a_{2}..a_{n}$, let $c=a_{i}a_{j}$ where $a_{i}\geq1$ and $a_{j}\leq1$. We know we can pick these because otherwise the product must be less or than greater one.  Then $c(a_{1}a_{2}...a_{n})= 1$ where $i\neq j$ and $i\neq k$ and by the induction hypothesis:  $$(c+1)(a_{1}+1)(a_{2}+1)...(a_{n}+1)\geq 2^{n-1}$$  And $$(1+a_{i})(1+a_{j})=a_{i}a_{j}+a_{i}+a_{j}+1$$  We want to show this product is greater than $2(c+1)$.  $$(1-a_{j})\geq (1-a_{j})$$  $$a_{i}(1-a_{j})\geq (1-a_{j})$$ since $a_{i}\geq 1$.  $$a_{i}-a_{i}a_{j}\geq (1-a_{j})$$  $$a_{i} + a_{j} \geq a_{i}a_{j} + 1$$  $$a_{i} + a_{j} + (a_{i}a_{j} + 1) \geq a_{i}a_{j} + 1 + (a_{i}a_{j} + 1)$$  $$(1+a_{i})(1+a_{j}) \geq 2(a_{i}a_{j} + 1) = 2(c+1)$$  Finally:  $$(1+a_{i})(1+a_{j})(a_{1}+1)...(a_{n}+1)\geq 2(c+1)\frac{2^{n-1}}{c+1}=2^{n}$$  Note: This exercise comes from Udi Manber's Intro to Algorithms.

Suppose $a_1, a_2,\dots , a_n$ are $n$ positive real numbers with $a_1a_2 \dots a_n = 1$.   Then what is the minimum value of $(1 + a_1)(1 + a_2). . .(1 + a_n)$ ?    I think $(1 + a_1)(1 + a_2). . .(1 + a_n)$ takes its minimum value when $a_1=a_2=\dots=a_n=1$ and thus the minimum value is $2^n$.  I don't know how to prove it. Please help.


I read that there is a feature to save videos using CTRL+SHIFT+ALT+R and I decided to try it:   I pressed the combination Did some silly things to get recorded  Pressed the combination once more I went to check out the webm file created   To my surprise, the video is 0 bytes big. How could this be? Do I have something misconfigured?  EDIT: To be clear, this problem affects only screencasting. Taking screenshots works without a problem.

After upgrading to Ubuntu 17.10 I noticed some of my screencasting applications are not working, for example screencasting tools like SimpleScreenRecorder and vokoscreen. ()  Also I noticed features like screenshot from GIMP is not working properly, producing blank screenshots (). Shutter too is producing glitchy screenshots ().  Screen-sharing option on Skype is also not working ().  The issue occurs sometimes on later Ubuntu releases too.  Why is this happening and how do I fix this?


Trying to delete a zone file from a name server (remote) from a local machine (connecting to the remote server with a key pairing). Script on the name server is below (remzone) which is executable. #!/bin/bash sed -i '/$1/,+4d' /etc/named.conf rm -f /var/named/slaves/$1.db rndc reload echo "$1"  The local command I am running is..... ssh root@server '~/remzone domain.com'  When I run the command locally, the following output is provided. me@Main:~$ ssh root@server '~/remzone domain.com' server reload successful domain.com  When executing the command locally, the domain.com.db is removed from /var/named but it does not remove the matching line (+4 lines) from /etc/named.conf. Zone    "domain.com" IN {         type slave;         masters {XXX.XXX.XXX.XXX;};         file "slaves/domain.com.db"; };  When I run sed -i '/domain.com/,+4d' /etc/named.conf on the nameserver directly, it deletes the zone file correctly from the /etc/named.conf file. Any Ideas?

I cannot not use a shell variable in sed in the $NUMBER form. I have this line in my shell script:  cat shared.txt sed 's/whatever1/$2 ... whatever2/' > shared2.txt   The result in shared2.txt looks like:  ...$2....   What did I do wrong?


How to prove ? How did Kepler proved it? Is it possible to prove the third law without applying Newton's universal law of gravitation?

Is there a simple way to explain how Kepler's third law follows from the inverse square law that of gravity  (and laws of motion)  For example for Kepler's second law we can say it's because Gravity is a central force  What is it about the law of gravity which ultimately gives rise to Kepler's third law?


If  i have this string:  "0110100001100101011011000110110001101111"   How can I divide it at every eighth character into smaller strings, and put it into a list, so that it looks like this?:  ['01101000','01100101','01101100','01101100','01101111']   So far, I can't figure out how this would be possible.  I should mention, since my strings are in binary so the length is always a multiple of 8.

I have a Python script which takes as input a list of integers, which I need to work with four integers at a time.  Unfortunately, I don't have control of the input, or I'd have it passed in as a list of four-element tuples.  Currently, I'm iterating over it this way: for i in range(0, len(ints), 4):     # dummy op for example code     foo += ints[i] * ints[i + 1] + ints[i + 2] * ints[i + 3]  It looks a lot like "C-think", though, which makes me suspect there's a more pythonic way of dealing with this situation.  The list is discarded after iterating, so it needn't be preserved.  Perhaps something like this would be better? while ints:     foo += ints[0] * ints[1] + ints[2] * ints[3]     ints[0:4] = []  Still doesn't quite "feel" right, though.  :-/ Related question:


I am on Yosemite on Mac Air of mid 2011. Bluetooth Low Energy Supported : Yes LMP version : 0x6  Then why does Handoff not work ?

Is there a failure with OS X Yosemite?   I have a MacBook Air mid 2011, with:   Bluetooth Version 4.3  Bluetooth Low Energy Supported  LMP Version 0x6      Does somebody experience the same behaviour?


My folder Desktop changed to file Desktop (without extension, 6MB). How can I turn it back? I need that content.

By accident I've removed some folders (they were empty) in my home folder. I've created a new ones but they doesn't have proper icons etc... how can I recreate them step by step?


Although many users mostly type lowercase letters, why are all keyboards printed with uppercase letters?

Why are all the letters (A, B etc) and all the writings (Home, Page Up etc) on the keyboard, capitalized?    Especially, the letters, because a new user could rightly expect uppercase letters to be entered upon pressing those keys to find the contrary.


I am actually trying to prove that $x^p - t$ is irreducible in $\mathbb{F}_p(t)[x]$. My approach is to consider a splitting field $E$ so that: $$x^p - t = (x-\alpha_1)\dots(x-\alpha_p)=(x-\alpha)^p   \ \ \ \ \text{for some $\alpha$ in $E$}$$ Then assuming by contradiction that $x^p - t = f(x)g(x)$, then $f(x) =(x-\alpha)^r$ with $r<p$. This implies that $\alpha \in \mathbb{F}_p(t)$. Should this be a contradiction right? Why can't $\alpha$ be here?

I don't think I fully understand.  Let's say there is a root $x_0 \in K=\mathbb{F}_p(t)$, where $p$ is a prime number.  Then $x_0 = \frac{P(t)}{Q(t)}$ for some polynomials $P,Q \in \mathbb{F}_p[t]$. We can assume $\gcd(P,Q)=1$  and $x_0^p-t= \frac{(P(t))^p}{(Q(t))^p}-t= \frac{P(t)^p-tQ(t)^p}{Q(t)^p} =0$, so coefficients of $P(t)^p, tQ(t)^p$ must be identical, which contradicts $\gcd(P,Q)=1$,   hence such $x_0$ does not exist and the polynomial has no root in $K$.   am I about right?    anyway, I would appreciate an explanation about $\mathbb{F}_p(t)$, what is $t$? what is the meaning of a variable which does not belong to any specific "world"? I cannot use $t$ as if it was a member of $\mathbb{F}_p$ and hence cannot assume $t^{p-1} = 1 \pmod p$...


How can I determine the dimensions of a cone with surface area 1 and maximal volume?

The problem I've got here is to prove that semi vertical angle of a cone with maximum volume with total surface area constant is equal to $arcsin(\frac{1}{3})$ I am trying to do that by making some relation in terms of trigonometric equations and then differentiating it. Supposing slant height is $l$ and semi vertical angle is $\theta$ then radius becomes $r=l\sin(\theta)$ and height becomes $h=l\cos(\theta)$ Given $$S=\pi r^2+\pi r l=constant$$ $$V=\frac{1}{3}\pi r^2h$$ but somehow i am not able to get the exact relation between  $$V=\frac{1}{3}l^2\cos^2(\theta).l\sin(\theta)$$ then I am taking Derivative of Function $V(\theta)$ and equating to zero to get maxima , but it's not working out , help ?


I'm trying to dual-boot Win10 and Ubuntu 18.04 LTS, if that matters. I have made a partition for Ubuntu, changed my SSD from RAID to ACHI mode, and disabled fast-boot. I have a Nvidia GTX1060.  I've been trying to install Ubuntu on my XPS 8900, and I noticed that my computer is not compatible with Ubuntu. When running the installer, the kernel gives me the error:   kernel: tpm_crb MSFT0101:00: [Firmware Bug]: ACPI region does not cover the entire command/response buffer. [mem 0xfed40000-0xfed4087f flags 0x201] vs fed40080 f80   kernel: tpm_crb MSFT0101:00: [Firmware Bug]: ACPI region does not cover the entire command/response buffer. [mem 0xfed40000-0xfed4087f flags 0x201] vs fed40080 f80   Also, the installer hangs when it gets to creating partitions. I've heard that you can fix this by editing the grub command line to boot the kernel with the following line of code:   pcie_aspm=off   So, how do I fix the first error, edit the grub code, make my system compatible, and do anything else I need to do to install correctly?

I can't boot Ubuntu 17.10  [    7.872529] tmp_crb MFST0101:00: [Firmware Bug]: ACPI region does not cover the entire command/response buffer. [mem 0xfed40000-0xfed4087f flags 0x200] vs fed40080 f80   There are two lines like that.  What should I do?


As far as I know, it is possible to have multiple A records for one host - GitHub Pages for apex domain is an example:  185.199.108.153  185.199.109.153  185.199.110.153  185.199.111.153  It is done for load balancing, Geo DNS purposes, etc.  So, what about several CNAME records for www? I have seen the setup for one domain recently that looked something like this:  www  CNAME whispering-willow-5678.herokudns.com.  www  CNAME autumn-sunset-1495.herokudns.com.  and it somehow managed to work via www.  My questions relate to the CNAME record particularly.   Are these CNAME records queried in turn? Is it possible to have the configuration (with multiple CNAME) this way or is it a blunder? Can such configuration be used for load balancing purposes or something?

I need this for load balancing. For example, I've two azure storage accounts (say a and b) and the blob addresses for those are a.blob.core.windows.net and b.blob.core.windows.net. Both of them store identical data. Now I need to provide a single external name (say example.com) which points to both the storage accounts and should work in round robin. This can be achieved if I create two CNAME entries in DNS as following and it resolves to one of them in round robing.   example.com CNAME a.blob.core.windows.net  example.com CNAME b.blob.core.windows.net   But I can not create two CNAME records for a single name in Windows DNS server.  So is it ever possible?


Does this matter or not? My motherboard is gigabyte. Thanks

My hostname is localhost, reported by hostname command, and terminal prompt root@localhost:~#.  How can i change it to mismis.com with mismis alias? and what is the proper configuration.  I confused after reading some articles on web.  My /etc/hosts:  127.0.0.1       localhost 127.0.1.1       srv345.myweb.com      srv345 178.162.231.61  janstone.mismis.com    janstone # The following lines are desirable for IPv6 capable hosts ::1     localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters


I overloaded a function like the following:  void myClass::saveAsMat (bool complete){   ... }  void myClass::saveAsMat (std::string filename){   ... }   In my main.cpp when I call the function like this:  myObj.saveAsMat(true);   everthing works fine. But when I instead call the function like this:  myObj.saveAsMat("myName");   the function is not being executed at all. I expected a compile or runtime error but there is nothing like that. The program gets compiled and runs only that the function is ignored. (I checked this by placing some std::cout inside the function).  Then I found out that I can solve this by changing the argument passed to:  myObj.saveAsMat(string("myName"));   Why do I have to set the extra string() for the argument? Other functions that are not overloaded are working fine by simply passing "myName" for a "std::string" paramenter.

Having recently introduced an overload of a method the application started to fail. Finally tracking it down, the new method is being called where I did not expect it to be.  We had  setValue( const std::wstring& name, const std::wstring& value );  std::wstring avalue( func() ); setValue( L"string", avalue ); std::wstring bvalue( func2() ? L"true", L"false" ); setValue( L"bool", bvalue ); setValue( L"empty", L"" );   It was changed so that when a bool value is stored we use the same strings (internal data storage of strings)  setValue( const std::wstring& name, const std::wstring& value ); setValue( const std::wstring& name, const bool& value );  std::wstring avalue( func() ); setValue( L"string", avalue ); setValue( L"bool", func2() ); setValue( L"empty", L"" ); << --- this FAILS!?!   The problem with L"" is that it is implicitly casting and previously it was happy to be a std::wstring, but not it prefers to be a bool. The MSVC compiler does not complain, or raise warning, so I'm worried that even if I "fix" the setValue( L"empty", L"" ); to be  setValue( L"empty", std::wstring() );   somebody else may come later and simply use setValue( L"empty", L"" ); and have to track down this issue again.  We thought to use explicit on the method but it is not a valid keyword for this usage. Is there some way to get the compiler to complain about this, or otherwise prevent the issue?  Otherwise I'm thinking to change the name of the method which takes a bool to ensure it can't make an incorrect guess.


For clarification, I'm not asking about getting the games to simply work on modern hardware/software. A lot of old DOS games had low max resolutions. Many (like Jagged Alliance: Deadly Games) maxed out at 640x480. Modern monitors have such high PPI (pixels per inch) that playing at the native resolution puts the game into a tiny letterbox. Playing fullscreen stretches the textures out causing a pixelated mess. Is there a good way to display these games at a good size without just getting a monitor with a lower PPI? I suspect there's no good solution but maybe something exists that's better than what I do, which is just play in a tiny window.

As many of you probably know, quite a few games on sites like GOG.com use Dosbox to start games which otherwise would be unplayable, due to their age. The graphics of such games (when played full screen on today's monitors) are abhorrent, of course.  For this reason, Dosbox offers to start the games with hardware acceleration (I use Direct3D), and to use a scaling engine to upscale the game to modern-day resolutions. The problem is that with most of these scaling engines, the picture becomes really small in fullscreen, since even when the picture is enlarged 3x, the resolution is too small. Dosbox offers no workaround for this (either have a very pixelated picture, or a small one).  However, then I saw videos such as this one , where the author claims to play the game at 1920x1200 (my own resolution), with a scaling engine termed HQ6x. The game looks quite gorgeous (if slightly cartoony). Problem is, in vanilla Dosbox, the highest scaler you get is HQ3x, and I couldn't find any scalers higher than that to download and easily install into Dosbox  Even after an hour of googling, I turned up empty. Is it possible to download, install and use a better scaling engine than what is available in vanilla dosbox, and if so, how?


I successfully defended my master's thesis last December.  I had 18/20 and it went well. However, my adviser invited me to carry out research in the area, which I accepted.   When I was writing the first paper, I noticed a big error in the data analysis. This does not affect the conclusions and the values of the estimates are very similar (with and without the error) the question is what do I do now? I'm afraid to tell my advisor and they cancel my master's degree. What do you think? My ethics does not allow me to write the paper again with the error, but if correct my advisor will find ..   Any suggestions? I'm sure no one will notice the error, but I do not know.  I´m very afraid of this Thank You

I finished my master thesis 6 years ago, since then I gained a lot of experience on my field and also in academia. I can say that in that time I was a "child" , very inexperienced. I think that also my advisor did not help a lot, and I tried to do  a lot of things by my own, without someone to really review my things. Despite that, I still received a good mention by the master committee on final results.   Some days ago, I just decided to read part of master thesis, and I just realized a big nightmare coming. I identified a lot of typos, some references errors, and some improvements that I should do, but I did not. The worst thing is that I wrote a paper to a conference with my master thesis results (and some errors are there). The conference is not a high impact conference, but still the paper has my name and is available for everyone...   As I am finishing my PhD studies for now, I am concerning a lot that situation. My dream and goal is to pursue a Professor career. So, my questions are: What are (or could be) the consequences of a master thesis and paper with errors (some minor and some major) in academia? Revoke degree after years by errors in master is possible ( I am concerning a lot this situation that I thought on it)? How can I minimize it (I thought that I can put a fixed version of my thesis and paper in the future, for instance on my personal website)? How those errors can impact me in a Professor recruitment process?  Sorry for the long text, I am blaming myself all the time, and really afraid about the possibilities since I know that Academia career is really competitive.


I'm testing out the iOS app for SE and I like it so far (in fact, I'm posting this from it), but I believe I've found a bug of some sort: I'm not allowed to edit posts. I can click on the edit link, but as soon as I press "preview" an error comes up suggesting that I don't have the reputation to do this.   I have 166 reputation on SO (which is where I tried to perform the edit), which allows me to suggest edits (and works fine on a desktop PC) but I can't do it on my iPhone 5.   Is this a bug? Or has something changed recently that I've missed?

I get this message while trying to edit a post on SuperUser while using the iOS mobile app. I have at least 101 reputation on SU, more than enough to be able to edit posts. This appears to be a bug.


How many strings with seven or more characters can be formed from the letters in EVERGREEN if the two R's are consecutive?  I know how to do this if the two R's don't have to be consecutive. Please point me in the right direction.


In AIP template using revtex4-1.cls I want to renew correctly the command \date{}    I just want to replace the output by \today instead of (Dated: \today).  What is the best way to do it in this sample of code ?   \documentclass[  aip,  jmp,  amsmath,amssymb,  reprint, ]{revtex4-1}  \usepackage{graphicx}% Include figure files \usepackage{dcolumn}% Align table columns on decimal point \usepackage{bm}% bold math  \begin{document}  \title[Sample title]{Sample Title}% Force line breaks with \\ \thanks{Footnote to title of article.}  \author{A. Author}  \altaffiliation[Also at ]{Physics Department, XYZ University.}%Lines break automatically or can be forced with \\ \author{B. Author}%  \email{Second.Author@institution.edu.} \affiliation{  Authors' institution and/or address%\\This line break forced with \textbackslash\textbackslash }%  \date{\today}% It is always \today, today,              %  but any date may be explicitly specified  \begin{abstract} Your abstract \end{abstract}  \pacs{Valid PACS appear here}% PACS, the Physics and Astronomy                              % Classification Scheme. \keywords{Suggested keywords}%Use showkeys class option if keyword                               %display desired \maketitle  \begin{quotation} Your lead paragraph \end{quotation}  \section{First Heading}  Article content \cite{small}.  \end{document}

I found the similar  for renaming some of the keywords, but they were for revtex4-1. Since my document is giving me strange errors when I'm using revtex4-1, and not when I'm using revtex4, this solution didn't help.   I also found  about revtex4 and there I found this:     The optional argument allows the user to override the text that will   be typeset along with the date; the default value of that text is   itself a localized macro.   1156\renewcommand*\date[2][\Dated@name]{\def\@date{#1#2}}% 1157\def\@date{}%   But this isn't working (or I don't understand how to use this)  Here's the 'mwe'  \documentclass[onecolumn,prb,floats,amsmath,amssymb,superscriptaddress,nofootinbib,12pt]{revtex4}  \usepackage{graphicx} \usepackage{bm} \usepackage[croatian]{babel} \usepackage{ucs} \usepackage[utf8x]{inputenc} \usepackage[dvipdfm,colorlinks=true,bookmarks=false,urlcolor=DarkOrchid,citecolor=ForestGreen,linkcolor=Cerulean,pdfstartview={XYZ null null 1.00}]{hyperref} \usepackage{extarrows} \usepackage{subfigure} \usepackage{caption} \usepackage{mathtools} \usepackage{bbm} %\usepackage{float} \usepackage{psfrag} \usepackage{url} \usepackage[all]{hypcap} \usepackage{subfigure} \usepackage[usenames,dvipsnames,svgnames,table]{xcolor} \usepackage{listings} \usepackage{array} \usepackage[paperwidth=210mm,paperheight=297mm,centering,hmargin=2cm,vmargin=2.5cm]{geometry} \usepackage{enumitem} \setlist{nolistsep} \makeatletter  \gdef\@ptsize{0}% 10pt documents  % or:  %\gdef\@ptsize{1}% 11pt documents  %\gdef\@ptsize{2}% 12pt documents  \let\@currsize\normalsize  \makeatother  \usepackage{setspace}  \onehalfspacing  \renewcommand*\date[2][\Dated@name]{\def\@date{#1#2}}% \def\@date{Datum:}%  \renewcommand{\tocname}{Sadržaj}  \makeatletter \renewcommand{\thesection}{\arabic{section}} \renewcommand{\thesubsection}{\thesection.\arabic{subsection}} \renewcommand{\thesubsubsection}{\thesubsection.\arabic{subsubsection}} \makeatother   \DeclareCaptionFont{white}{\color{white}} \DeclareCaptionFormat{listing}{\colorbox{gray}{\parbox{\textwidth}{#1#2#3}}} \captionsetup[lstlisting]{format=listing,labelfont=white,textfont=white}  \newcolumntype{y}[1]{>{\centering\let\newline\\\arraybackslash\hspace{0pt}}p{#1}} \renewcommand*{\arraystretch}{1.2}   \begin{document}  \title{Random title} \author{Random guy} \affiliation{Random place, 99999 Randomville} \date{\today}  \begin{abstract}  \end{abstract}  \maketitle  \begingroup \hypersetup{linkcolor=black} \tableofcontents \endgroup   \section{Intro}  \section{Bla}  \subsection{Bla1}   \section{Bla!}   \end{document}


I have a model edited with blender. I selected all my meshes and made CTRL-A to reset scale and location. Since then, 8 of my meshes have some akward kind ob cube around them. What is it and how can I hide these cubes? I must have done a bad manipulation here but I don't know when and how I made it. Google is not helping me there neither.

When I attempt to triangulate a mesh I end up with that dotted yellow bounding box when I mistakenly press Shift+t instead of Ctrl+t.  I cannot get rid of it by using Undo.    From what I can tell, it has something to do with Texture Space but I cannot find anything in the Object Data panel that will remove it once it's there.    So does anyone know how to get rid of this and set things back to how they were before I hit that wrong shortcut?


$$\int_0^2f(x)\,\mathrm dx=\int_0^2 f(t)\,\mathrm dt.$$  I would say true because a&b = a&b and it would not make a change if is x,d,f,q,w,t it will logically be all the same, am I right ? but because it is MATH not logic so everything could be unexpected!

I will be TA this semester for the second course on Calculus, which contains the definite integral.  I have thought this since the time I took this course, so how do I convince my students that for a definite integral   $$\int_a^b f(x)\ dx=\int_a^b f(z)\ dz=\int_a^b f(☺)\ d☺$$  i.e. The choice of variable of integration is irrelevant?   I still do not have an answer to this question, so I would really hope someone would guide me along, or share your thoughts. (through comments of course)  NEW EDIT: I've found a relevant example from before, that will probably confuse most new students. And also give new insights to this question.  Example: If $f$ is continuous, prove that   $$\int_0^{\pi/2}f(\cos x)\ dx = \int_0^{\pi/2}f(\sin x)\ dx$$  And so I start proving...  Note that $\cos x=\sin(\frac{\pi}{2} -x)$ and that $f$ is continuous, the integral is well-defined and  $$\int_0^{\pi/2}f(\cos x)\ dx=\int_0^{\pi/2}f(\sin(\frac{\pi}{2}-x))\ dx $$  Applying the substitution $u=\frac{\pi}{2} -x$, we obtain $dx =-du$ and hence  $$\int_0^{\pi/2}f(\sin(\frac{\pi}{2}-x))\ dx=-\int_{\pi/2}^{0}f(\sin u)\ du=\int_0^{\pi/2}f(\sin u)\ du\color{red}{=\int_0^{\pi/2}f(\sin x)\ dx}$$  Where the red part is the replacement of the dummy variable. So now, students, or even some of my peers will ask: $u$ is now dependent on $x$, what now? Why is the replacement still valid?  For me, I guess I will still answer according to the best answer here (by Harald), but I would love to hear more comments about this.


So the problem states that if $f(z)$ is entire, and satisfies the relation $f(z+i) = f(z)$ and $f(z+1) = f(z)$, show that $f(z)$ is constant. So I was thinking that since any point in $\mathbb{C}$ can be written as $\alpha * 1 + \beta * i $ we can say that $f(z + z_0) = f(z) $ in which case it is constant, but I'm having trouble breaking down the steps, and using the fact that f is entire, which makes me feel like I'm missing something. What should I review to figure this out?

Let $f: \Bbb C \to \Bbb C$ be an entire (analytic on the whole plane) function such that exists $\omega_1,\omega_2 \in \mathbb{S}^1$, linearly independent over $\Bbb R$ such that: $$f(z+\omega_1)=f(z)=f(z+\omega_2), \quad \forall\,z\in \Bbb C.$$Prove that $f$ is constant.   The intuition seems clear to me, we have the three vertices of a triangle given by $0$, $\omega_1$ and $\omega_2$. All points in the plane are one of the vertices of that triangle under a suitable parallel translation. The constant value will be $f(0)$, fine. Throwing values for $z$ there, I have found that $$f(n\omega_1) = f(\omega_1) = f(0)=f(\omega_2) = f(n\omega_2), \quad \forall\, n \in \Bbb Z.$$  I don't know how to improve the above for, say, rationals (at least). Some another ideas would be:   Checking that $f' \equiv 0$. I don't have a clue of how to do that. Write $w = a\omega_1+b\omega_2$, with $a,b \in \Bbb R$, do stuff and conclude that $f(w) = f(0)$. This approach doesn't seem good, because I only have a weak result with integers above. Finding that $f$ coincides with $f(0)$ on a set with an accumulation point. This seems also bad: the set on with $f$ coincides with $f(0)$ by which I found above is discrete.    Nothing works and this is getting annoying... And I don't see how analyticity comes in there. I'll be very thankful if someone can give me an idea.  (On a side note.. I know that this title is not informative at all. Feel free to edit if you come up with something better.)


For the architectural side of rendering, there's two main ways: having each object render itself, and having a single renderer which renders everything.  I'm currently aiming for the second idea, for the following reasons:   The list can be sorted to only use shaders once. Else each object would have to bind the shader, because it's not sure if it's active. The objects could be sorted and grouped. Easier to swap APIs. With a few macro lines, it can be easy to swap between a DirectX renderer and an OpenGL renderer (not a reason for my project, but still a good point) Easier to manage rendering code   Of course, if anyone has strong recommendations for the first method, I will listen to them.  But I was wondering how make this work.     First idea The renderer has a list of pointers to the renderable components of each entity, which register themselves on RenderCompoent creation. However, I'm worrying that this may end up as a lot of extra pointer weight. But I can sort the list of pointers every so often.  Second idea The entire list of entities is passed to the renderer each render call. The renderer then sorts the list (each call, or maybe once?) and gets what it wants. That's a lot of passing and/or sorting, however.  Other ideas ??? PROFIT  Anyone got ideas? Thank you.

I am very new to game development, but not to programming.  I am (again) playing around with a Pong type game using JavaScript's canvas element.  I have created a Paddle object which has the following properties...   width height x y colour   I also have a Pong object which has properties such as...   width height backgroundColour draw().   The draw() method currently is resetting the canvas and that is where a question came up.  Should the Paddle object have a draw() method responsible for its drawing, or should the draw() of the Pong object be responsible for drawing its actors (I assume that is the correct term, please correct me if I'm incorrect).  I figured that it would be advantagous for the Paddle to draw itself, as I instantiate two objects, Player and Enemy. If it were not in the Pong's draw(), I'd need to write similar code twice.  What is the best practice here?  Thanks.


I am an experienced user of LaTeX learning ConTeXt. However, I find the manuals on the PRAGMA website to be less than ideal. Does anyone have a suggestion for a manual or text?

Where would be a good place to start learning ConTeXt if you haven't got a lot of experience under your belt yet? Any place online or in a bookstore is welcome, provided that the reading is well-structured, well-written and beginner-friendly.  I know there is quite a heap of "official documentation", including "ConTeXt, an excursion", the official handbook and the contextgarden.net Wiki.   Still, often ConTeXt novices find it very difficult to get a good start with the documentation provided -- the command syntax seems to work sometimes, sometimes not; some commands work well with each other, others only in a specific order (which isn't documented anywhere) and some don't work with each other at all etc. The consequence is that there is a lot of experimenting with the code while the focus should be on the topic to be published itself.  This question would love to get RTFM answers, so please point out any Ms which should TF be R.


Let $f,h,g\in L^{2}(\mathbb R^2).$ Prove the inequality   $$\int_{\mathbb R^3}\vert f(x,y)g(y,z)h(z,x)\vert d(x,y,z)\leq\|f\|_2\|g\|_2\|h\|_2.$$   Using Fubini's Theorem and the Cauchy-Schwarz Inequality I obtained the following string of inequalities $$\int_{\mathbb R^3}\vert f(x,y)g(y,z)h(z,x)\vert\,d(x,y,z)\leq\|f\|_2\int_{\mathbb R}\left[\int_{\mathbb R}\int_{\mathbb R}\vert g(y,z)h(z,x)\vert^2\,dx\,dy\right]^{1/2}dz,$$ $$\int_{\mathbb R^3}\vert f(x,y)g(y,z)h(z,x)\vert\,d(x,y,z)\leq\|g\|_2\int_{\mathbb R}\left[\int_{\mathbb R}\int_{\mathbb R}\vert f(x,y)h(z,x)\vert^2\,dy\,dz\right]^{1/2}dx,$$ $$\int_{\mathbb R^3}\vert f(x,y)g(y,z)h(z,x)\vert\,d(x,y,z)\leq\|h\|_2\int_{\mathbb R}\left[\int_{\mathbb R}\int_{\mathbb R}\vert f(x,y)g(y,z)\vert^2\,dx\,dz\right]^{1/2}dy,$$ which I think, upon multiplication of all three, lead to nothing.  After that I tried using again Fubini's Theorem and this time Minkowski's Integral Inequality, but that leads to a similar string of inequalities, once again leading nowhere.    Can anyone please recommend me something to try to get started on this problem?  Thank you for your time and I apologize for my failure to solve the problem or come up with a more clever attempt.

Let $f_1,f_2,f_3:\mathbb{R}^2\to\mathbb{R}_{\ge 0}$ be measurable, bounded, and compactly supported. Prove that  $$\int_{\mathbb{R}^3}f_1(y,z)f_2(x,z)f_3(x,y)d(x,y,z)\le\lVert f_1\rVert_{L^2(\mathbb{R}^2)}\lVert f_2\rVert_{L^2(\mathbb{R}^2)}\lVert f_3\rVert_{L^2(\mathbb{R}^2)}$$ By Tonelli's Theorem and Cauchy, \begin{align} \int_{\mathbb{R}^3}f_1(y,z)f_2(x,z)f_3(x,y)d(x,y,z) &=\int_{\mathbb{R}^2}\left(f_1(y,z)\int_{\mathbb{R}}f_2(x,z)f_3(x,y)dx\right)d(y,z)\\ &\le\sqrt{\int_{\mathbb{R}^2}f_1^2(y,z)d(y,z)\int_{\mathbb{R}^2}\left(\int_{\mathbb{R}}f_2(x,z)f_3(x,y)dx\right)^2d(y,z)} \\ &\le\lVert f_1\rVert_{L^2(\mathbb{R}^2)}\sqrt{\int_{\mathbb{R}^2}\left(\int_{\mathbb{R}}f_2^2(x,z)f_3^2(x,y)dx\right)d(y,z)} \\ &=\Vert f_1\Vert_{L^2(\mathbb{R}^2)}\sqrt{\int_{\mathbb{R}^3}f_2^2(x,z)f_3^2(x,y)d(x,y,z)} \\ &=\lVert f_1\rVert_{L^2(\mathbb{R}^2)}\sqrt{\int_{\mathbb{R}^2}\left(f_2^2(x,z)\int_{\mathbb{R}}f_3^2(x,y)dy\right)d(x,z)} \\ &\le\lVert f_1\rVert_{L^2(\mathbb{R}^2)}\sqrt[4]{\int_{\mathbb{R}^2}f_2^4(x,z)d(x,z)\int_{\mathbb{R}^2}\left(\int_{\mathbb{R}}f_3^2(x,y)dy\right)^2d(x,z)} \end{align}  As you can see, this doesn't seem to be going anywhere.


Give an example of a continuous function $f:R\rightarrow R$ which attains each of its values exactly three times.    Ed.: answered by the duplicate above   Does there exist a continuous function $f:R\rightarrow R$ which attains each of its values exactly two times?   Ed.: answered by

Does there exist a function $f: \mathbb{R} \to \mathbb{R}$ that takes each value in $\mathbb{R}$ three times? If not, how could I prove that such a function does not exist?


Story Details/Summary  The protagonist is either an American or British combat pilot.  He's currently flying to a base in Europe, but when he touches down on a rather primitive landing strip, he discovers that somehow, he and his jet aircraft have been hurled back to the time of the Great War.   There is the usual confusion and "how did THIS happen?!?" on the part of the protagonist, but he gradually accepts that he has landed on an allied airbase smack in the middle of the war.  The protagonist's contact in the story is a British, or perhaps French, officer who acts as his go between throughout much of the story.  Once acclimated to the reality of his surroundings, the pilot is eager to join the fight against the Central Powers.  Specifically, he is willing to take the fight to a German squadron of biplanes that have been pummeling this particular airbase and thwarting attempts to advance friendly ground forces against the enemy.  Naturally, the pilot believes the huge technological advantage of his modern fighter jet will allow him to smash the German air forces easily.  I do not recall the particular model of the jet the pilot flies.  It might have been a real-world design, or a fictional one.  I do recall that the plane's design is very much in keeping with American fighters and strike aircraft of the early 60's.  That is, big, powerful and fast, with sophisticated equipment and armed with missiles.  The plane does not have guns of any sort, nor is it particularly maneuverable (in keeping with the "dogfighting is a dead art" doctrine of that era).  It's also a thirsty beast, and the protagonist asks the other officer to requisition several thousand liters of refined kerosene (i.e. jet fuel).  When the German air forces launch their next attack, the protagonist takes flight.  IIRC, he tells the other officer to keep his planes on the ground and well away from the battle.  I believe this is because one or more of the long-range missiles on his aircraft are nuclear-tipped.  The protagonist engages the enemy at long range, selecting choice targets and firing missiles at them.  Unfortunately, the attack is a complete failure.  Each of the missiles fails to lock on to its target, and fizzle out when their fuel is expended.   The pilot realizes that the German biplanes are made mostly of wood and canvas, and there's not enough heat or radar signal generated by the planes for the sensors in the missiles to lock on to them.  The protagonist chides himself that he should have gone after the enemy airfield hangars with his missiles.  As he has no guns on his jet, he can do nothing but return to base.  The pilot touches down, bitterly disappointed.  The other officer is sympathetic, though disappointed.  The protagonist stews about what to do next.  There is a line about how the powerful radars in his jet can cook a man alive, but it would take hours against a target standing completely still.  Eventually, he comes upon an idea.   He pleads with the other officer to requisition more refined kerosene.  The man is reluctant, but eventually does so.  The climax of the story comes with the protagonist once again facing the German squadron.  This time, though, he has the means to defeat them.  He accelerates to maximum speed, using the afterburners to go supersonic, and rockets straight through their formation.  The shock wave of the supersonic boom is too much for the fragile biplanes, and their wings are ripped to pieces.  The entire squadron is destroyed mid-air.  The story closes with the protagonist landing his jet one last time, and the exultant officer and others cheering the dramatic victory over a foe they thought unbeatable.  Publication Timeframe  I'd guess this one would be late 1950's to early 1960s.  That would seem to be about the right era for the technology of the protagonist's jet.

Looking for title and author of a short story.  A pilot of an (American?) near-future military jet and his machine find themselves back in time on an airfield near the front line in World War I. The pilot decides to use the awesome power of his modern machine to aid the allied cause. However he encounters problems. It takes a huge amount of time and effort filtering lamp oil to make the fuel his jet needs. The wooden enemy planes don't show up on radar, and his heat seeking missiles won't lock into them. The WWI pilots are generally skeptical of his machine's capabilities. I believe the aircraft may have been called something like "Pica Don".  The story is English, and I read it around the nineties. Oh, and absolutely positively no aircraft carriers are involved.


I am using QGIS 2.2 Valmiera to try to find the average slope of a water course. I've drawn in the water course as a polyline over a large number of contour lines (the water course is long with a very large catchment area).  What I've tried to do so far is create a tin file. I've used the Raster > interpolation function using the heights attribute of the contour line shapefile to make the tin and each time I try it gives me a mini-dump error.  I've tried to simplify the geometry (from 392515 to 66801 vertices) but I still just get the mini-dump error.  Is there another way to get the slope of this polyline without having to make a tin file or am I doing something wrong in trying to make the tin?

I have a shapefile with contours and their heights.   Is it possible to make a DEM from contours in QGIS without using GRASS?   I found  but the answer is for ArcGIS Desktop.


I see numbers like this in calculators, but they don't mean anything to me. How do I turn this number into a real number.  9.223372e+18  I'm not even sure what kind of math this is.

Hey all I asked this over  =) and I got a good answer but I still have no idea whats going on. I want to know how the expression got to the answer and maybe the math behind how it was reasoned.. the steps if you would be so kind. The likelihood is I don't understand the equation.   I'm not a big maths person please be gentle :p     For all those playing along at home I'm reading Absolute Java 5th   Edition by Walter Savitch (Chapter 2 Page 66).      The Expression  double d = 12345.123456789; System.out.printf("START%12.5e END %n", d);       The Answer  START 1.23451e+04END       I understand the basic principles of this printf method's arguments   for example I know the '%' represents the start of the parameters.   '12' is the number of spacing, '.5' is the times the decimal point   will move.... I see the decimal point has moved 4 places towards the   left... can someone explain the principles of e-notation. Also how   this expression came to this answer =).      As far as e-notation go's its meant to be scientific notation;      So like 5.89e-4 would mean 0.000589 (move the decimal place if minus   left if not move the decimal place right).


The proof is given below:    But I do not understand the statement in the line before last which says "These give rise to the single congruence $a ^{560} \equiv 1 \pmod n$ where gcd(a, 561) = 1 ", I do not know why the previous mentioned system of linear congruences leads to this single congruence, what theorem is used to say this? is it the Chinese Remainder theorem ? if so how?

A composite integer n is a Carmichael number if the only Fermat   witnesses for $n$ are those $a \in \mathbb Z_n^+$ which are not   coprime with $n$. The smallest example of such a number is $561 = 3 ·  11 · 17$   I think I understand the definition, but I don't quite understand why is the smallest Carmichael number is the above mentioned number. Please clarify.


I need to decide whether to show prices on a website with or without taxes.   At the moment our Product can be purchased for Rs.999. But we recently got a GST certificate and have to charge our customers 18% tax. I would like to know the best way to display the price of the product, the two ways that we can do this are either by:   Showcasing the price as "Rs.999+18% GST" and show the final split up at the payment portal. Showcasing the price as "Rs.1200(Inclusive of all taxes)" and show the split up at the payment portal.   We don't want to lose out on potential customers because we are showcasing a high price nor do we want to lose them because we are showcasing the price exclusive of taxes.  We ran a poll at my office and we reached a split decision on the same.  Some people preferred the price to be displayed as "Rs.999+18% GST" because:   They prefer to see how much the base price of the product was Some don't look into how much the tax amount is and only care about how much the product costs They are interested when they see the lower price   The other half chose "Rs.1200(Inclusive of all taxes)" because:   They didn't need to calculate tax A clear-cut price is shown It's a round off value  Some didn't want to see a split up and only wanted the final amount.   To give you all more perspective our target audience are final year college students and our company is based out of India.  What do you think is the best approach to this problem? Also I'm open to other solutions about how to go ahead with this issue.

I need to decide whether to show prices on an online store with or without taxes. This is significant for the site and the user as the service is labeled as the cheapest on the market.  If taxes wouldn't be included then we would tell the user explicitly (e.g. " X price + taxes". This is a B2C site so user will always pay full price (meaning he won't be able to deduct those taxes as business can).  I'm afraid this can cause sticker shock to our users at the moment of checkout and I don't like it as practice but could work (Amazon does that and I still end up paying for something...)  What do you guys think?


I am on 19.10 release which is not LTS, 20.x will be released in April, that time will I able to upgrade directy from 19.10 or I do downgrade to latest 18.x release for next LTS upgrade ?

If I install Ubuntu 18.10 (non LTS) now, then follow all the releases until next year where we will get the next LTS, will I (next year) be able to install the new LTS from my non LTS? I am not talking about downgrading, but upgrading to the next LTS from a non LTS system.


I designed my website logo for WordPress but it's too small, pixelated, and unappealing.  I'm designing my logo in sketch. What artbord size should I design on? What size do I export?  What size is the standard? How do I design a logo in sketch so it's high res? And not pixelated while PNG?

I'm pretty new to photoshop and illustrator and trying to create a simple text-based logo to use on my web site, for example:   You get wildly different versions of that depending on what browser you use to render the text (which is why I obviously must create the image myself), but for example on Chrome you can already see a blurriness around the edges of the font.  The problem I'm having in Illustrator is that when I write in a certain font (e.g. "Arial Rounded MT Bold" at 24pt), the font looks beautiful and crisp against my background colour at 200% zoom, but I start to see blurring at 100% - then I'm not sure what it is about the 'save to web' process, but the image loses further clarity by the time it ends up on my website (as a 'type optimised' png).  I'd read somewhere that photoshop was better for saving images of text for web, but I see a similar blurriness there even in advance of exporting (and of course a 200% zoom in photoshop just pixelates the image).  So what I'm really lacking is a step-by-step for-dummies type guide of how to get crisp images of text onto a website.  At this point I'm not sure if perhaps I've just chosen a bad colour contrast, or fonts that don't scale well - although I'm also wondering if there's something significant in the fact the font looks beautiful in Illustrator at 200% or larger - perhaps that means I should be exporting the font from Illustrator at a larger size than required and then doing additional downsizing (somehow!) afterwards - although of course again I can't trust web browsers to do that for me.  EDIT: I should also have noted that the effect is much worse on my monitor versus my laptop (tempting to say I have a bad monitor but there's many websites where the monitor version looks fine too!)


When the app starts and I try to immediately rotate the screen It gives me this error:  public void onDestroy() {         super.onDestroy();         appbars.animate().translationY(0).alpha(1).setDuration(100).setInterpolator(new DecelerateInterpolator());      }   Error:   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewPropertyAnimator  android.support.design.widget.AppBarLayout.animate()' on a null object  reference

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


I want to test the function replacefl for checking whether my "String s" has  undergone the required changes inside the function. Since the parameters passed in java are pass by values, so how can I test the behaviour of the parameter.   public class Abc{  void replcefl(String s){          s = s.subSequence(1, s.length() - 1).toString();      } }   The test class :   public class AbcTest{     Abc abc = new Abc();      @Test     public void testfl{        String testString="{Chandan}";        String resultString="Chandan";         abc.replacefl(testString);        assertEquals( resultString, testString);     }      }   Here the test case is not working because it is pass by value. Can you please help me out in how to write test case for this particular function which returns void.

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


I am planning to run a game of Nobilis on roll20 but I am having trouble finding people for it. Is there some sort of advertisement technique I can use in order to recruit players for my game?

I'd really like to learn how to play pen-and-paper RPGs.  I know that it takes a few players to actually sit down and play, but I'm not at all sure where to find more gamers.  How do I find existing groups to join? Or, are there any resources online that may help me find existing RPG groups or players?


More precisely, given the ring homomorphism $\phi:\Bbb{R}[x,y]\to\Bbb{R}^\Bbb{R}$, with  $\phi(f(x,y)):\Bbb{R}\to\Bbb{R},\,\,\phi(f(x,y))(\theta)=f(\cos(\theta),\sin(\theta))$, where $\Bbb{R}[x,y]$ is the ring of formal polynomials in two variables on $\Bbb{R}$, I wish to show that $\mathrm{ker}(\phi)=(1-x^2-y^2)$. So far the best I can do is to show that $\mathrm{ker}(\phi)\supseteq(1-x^2-y^2)$, which is pretty trivial anyway. In particular, I'm interested in a proof of this statement from the perspective of algebraic geometry.

Pythagoras says that $\cos^2 \theta + \mathrm{sin}^2\theta = 1$ for all real $\theta$.  (Vague) Question. Is this the only relationship between the functions $\cos$ and $\sin$?  More precisely:  Let $\langle \cos,\sin\rangle$ denote the intersection of all subalgebras of the $\mathbb{R}$-algebra of all functions $\mathbb{R} \rightarrow \mathbb{R}$ containing $\{\cos,\sin\}$. (By default, all my algebras are unital, associative and commutative.) Let $A$ denote the $\mathbb{R}$-algebra presented by the generators $\{c,s\}$ and the relation $c^2+s^2=1$. There is a unique $\mathbb{R}$-algebra homomorphism $\varphi : A \rightarrow \langle \cos,\sin\rangle$ given as follows. $$\varphi(c) = \cos, \,\,\varphi(s) = \sin$$  We know that $\varphi$ is surjective.     Question. Is $\varphi$ injective?   So consider $f \in A$. Then $f = \sum_{i,j : \mathbb{N}}a_{ij}s^ic^i$ for certain choices of $a_{ij} : \mathbb{R}$. Now suppose $\varphi(f)=0$. We want to show that $f=0$. Ideas, anyone?


Right now I'm designing a dungeon that is actually a ruined castle, but with illusion magic it appears to be restored to its original shape. One of the key parts I need is a window, which is actually an illusion, on a real, solid wall.  The party only needs to be able to look through this wall - so whether it's a glass window or (hollow?) window does not matter - while in a moment later, the illusion will be dispelled and the solid wall will be revealed.     What method can be used to achieve this kind of illusion: a see-thru window on a solid wall?      I'm aware I can just make the effect up, but I prefer a spell castable by a PC (or magic item) because this will serve as some sort of a memorial of a PC.    This does not strictly need to be an illusion, although I strongly preferred it to be one. I only need that, when the effect is active, it shows what's behind the wall. When the effect is inactive, it shows what's on the wall.  Maybe some sort of 'glow in the dark' ink, but this actually shows what's behind the wall.  If the method needs a certain interpretation over a rule or description, as long it does not stretch too much from RAW, I'm fine.

I've been thinking of various ways for a crafty Illusionist/Rogue to 'hide in plain sight' by essentially creating the cover that they want to hide behind.  Ideas include things like:   Create a wall that is 2.5ft closer than it really is and hide in said space Create some innocuous barrier or container and hide within it Create a 'sheet' that essentially has what an empty room looks like 'painted' on it, so someone walking past an open door would see an empty room.   From different discussions I've had, these all should work, but the one lingering one I have is, what if my illusion is simply 'empty space'?  If I were to create an illusion of empty space and then place myself in it, would I be essentially invisible?  What if I created an illusion that was partially-empty space, like a 5x5 cube of swiss cheese? Would it seem like there was a swiss cheese cube formed around my person or could my 'fake-empty-space-image' fill the holes?  Would my 'empty space' illusion simply need to work like the aforementioned 'sheet of what I expect you to see' in order to function (and thus most likely only work from limited viewing angles)?


So I'm very new to PostgreSQL (and SQL as a whole) and I'm trying to find a way to view all attributes of a table. For example, say you have a table called "movies", I would like to see what attributes it has (e.g. movie_name, release_year). I'm sure there is a simple command for it, but I couldn't find it. Thanks in advance for any help!

How do you perform the equivalent of Oracle's DESCRIBE TABLE in PostgreSQL (using the psql command)?


The instructions for Windows 8 does not work for Windows 7.  How do I remove the Password Eye from Windows 7.  Thank you.

I already read up on the answer as to how to remove the eye symbol (for password peek) from Windows 8. It also mentioned that since Windows 8's launch, the eye symbol also appeared on Windows 7, which is what I have.   The Windows 8 method uses the Local Group Policy editor in gpedit.msc, but I don't have that on Windows 7.  So how do I remove it from Windows 7?


When I look at my reflection in a planar mirror, the image I see is reflected about a vertical axis. Why is it this axis and not the horizontal axis?

Why is it that when you look in the mirror left and right directions appear flipped, but not the up and down?


Hi I wanted to know what the differences between returning and exiting from the main function are. What happens behind the scenes when each of them are invoked, and how is the control returned in each case. I would really appreaciate it if someone could dive deep into this subject.

Should I use exit() or just return statements in main()? Personally I favor the return statements because I feel it's like reading any other function and the flow control when I'm reading the code is smooth (in my opinion). And even if I want to refactor the main() function, having return seems like a better choice than exit().  Does exit() do anything special that return doesn't?


I installed clean CentOS 8 machine. copied my app to it. started. i can get response by curl https://localhost:5001 -- insecure but if I try a local or external ip or browser from remote location for example sudo firewall-cmd --zone=public --add-port 5001/tcp --permanent sudo firewall-cmd --reload  curl https://10.128.0.10:5001 -- insecure curl: (7) Failed to connect to 10.128.0.10 port 5001: Connection refused

This is a  about Connection Refused    We see a lot of questions to the effect      When I try to connect to a system I get a message      Connection refused      Why is this ?


I have a very basic Matlab/M function to take the first cell of a cell array, then return the cell removed and the rest of the cell array minus the first cell, like taking the first item out of a queue. Matlab seems to have a fit about the type of the input being a cell array. Is it possible to pass cell arrays into functions?  I saved the function with a filename the same as the function, i.e. fpop.m, and I double-checked my input, but I'm getting the error: Undefined function 'fpop' for input arguments of type 'cell'.  This is my simple function code:  function [cell, outqueue] = fpop(queue) % DELETE FIRST ELEMENT ONLY, RETURN REMAINDER %Queue  outqueue = {}; cell = {}; if size(queue,2) < 1     %do nothing elseif size(queue,2) < 2     cell = queue{1}; else     cell = queue{1};     for i = 2:size(queue,2)         outqueue{i-1} = queue{i};     end end   The code I used to call the function and the cell array input:  myqueue = {{1,2}, {3,4}, {5,6}, {7,8}, {9,10}}; [outpair, myarray] = fpop(myqueue);   I tested all the statements outside of the function, so I know everything is working. I just seem to have something wrong with the function call -- or perhaps passing a cell array into a function is just not possible.  I did some checking online, and the info I found says that I need to reference the specific part of the cell array I want to pass, essentially passing in not the cell array but the variable(s)/object(s) inside the cell. I don't want to pass in the objects individually though -- I want to pass in the entire array and then do work on the cell array. Is this possible?  Also, I found  here on SO, but none of the answers seemed to address the issue and since I don't know all the factors of the original issue, it seemed better to start a new question.

I'm a new user of Matlab, can you please help: I have the following code in an .M file:  function f = divrat(w, C) S=sqrt(diag(diag(C))); s=diag(S); f=sqrt(w'*C*w)/(w'*s);   I have stored this file (divrat.M) in the normal Matlab path, and therefore I'm assuming that Matlab will read the function when it's starting and that this function therefore should be available to use.  However, when I type  >> divrat(w, C)   I get the following error     ??? Undefined function or method 'divrat' for input arguments of type 'double'.     What is the error message telling me to do, I can't see any error in the code or the function call?


Looking for a book where people were in a spaceship to another planet, and when they reached the surface someone on earth had developed a portal and stepped onto the planet at the same time, wearing a crappy suit with a fishbowl for a helmet. The pilot of the spaceship being very angry because their voyage was supposed to be newsworthy, and here this guy and his friend covered the same distance instantly. this was the beginning of the book   Later in the book some guy has a home/ecosystem in an asteroid because he can.  Any ideas?

Desperate to locate and re-read exceptional book/series, but cannot remember the title. The high concept: The U.S. has just sent the first successful expedition to Mars, and it has just landed. As the astronauts make their initial exploration outside their ship, a tear in the fabric of space opens up right in front of them, and they look through to the insides of a laboratory (at a California university?) and two students who just figured out how to create arbitrary portals between two points in the Universe. The rest of the novel/series is a consequence of this breakthrough. But I can't remember the author and title(s). Surely someone reading this forum will remember it well! TIA.  (Reposted .)


"Calculate how many possible key pairs exist" Found these through searching. Not sure if either are correct. I would've assumed the number would be infinite. phi(n) - 1 phi(n)/2

What determines the number of possible RSA key pairs for a given $n$? Is it because $\varphi(n)$ produces the number of values that are less than $n$ and coprime with $n$? Is it as simple as $\varphi(n)$?


I'm trying to add a list of code listings to my document, with a reference to it in the TOC. By simply calling  \lstlistoflistings   I end up getting everything I need (the list of listings, an entry in the TOC, etc) EXCEPT for the fact that the entry is always named 'Contents'. I was able to change the title of the listing page itself by running the command   \renewcommand\lstlistlistingname{List of Code}   but this doesn't change the reference in the table of contents.  EDIT: Adding a minimal working example  \documentclass{Thesis}  \usepackage{listings}  \begin{document} \renewcommand\lstlistlistingname{List of Code}  \tableofcontents  \lstlistoflistings  \lstset{caption=Some Code} \begin{lstlisting} Some code \end{lstlisting} \end{document}

using the \lstlistoflistings always named as Contents in table of contents.  I did look into   and  but the solutions there did not work.  Example: (my complete preamble)  \documentclass[11pt, oneside]{Thesis}  \usepackage{tikz} \usepackage{pgfplots} \usepackage{pgfplots,filecontents} \usepackage{caption} \usepackage{subcaption} \usepackage{booktabs,colortbl} \usepackage{graphicx} \usepackage{rotating} \usepackage{listings} \usepackage{color} \usepackage{comment} \usepackage[official]{eurosym} \usepackage{colortbl} \usepackage{algorithm}  \usepackage{algpseudocode} \usepackage{indentfirst} \usepackage{latexsym} \usepackage{titlesec} \usepackage[square, numbers, comma, sort&compress]{natbib}   \hypersetup{urlcolor=blue, colorlinks=true}  \renewcommand{\lstlistlistingname}{List of Code}   \begin{document}  \tableofcontents \lstlistoflistings \lstinputlisting[language=python,firstline=1,lastline=68,caption=some caption here., label=code:getbb]{Code/getBoundingBox.py} \end{document}   The renew command changes the header in the page but not in the table of contents. Any ideas?  EDIT x2:  Managed to get the naming correct by editing this in the Thesis.cls   }  \renewcommand\lstlistoflistings{  \btypeout{List of Listings}  \addtotoc{List of Listings}  \begin{spacing}{1}{ \setlength{\parskip}{1pt} \if@twocolumn   \@restonecoltrue\onecolumn \else   \@restonecolfalse \fi \chapter*{\lstlistlistingname   \@mkboth{       \MakeUppercase\lstlistlistingname}{\MakeUppercase\lstlistlistingname}} \@starttoc{lot} \if@restonecol\twocolumn\fi \cleardoublepage  }\end{spacing}   Now the name appears correctly in the TOC but the Listings do no show in the Listings page, its just empty..  A MWE can be found here:


It seems generally admitted that there are no negative prime numbers.  What are the rules that can affirm this?  Thanks in advance and happy new year to all.  Best regards,

Do we have negative prime numbers?   $..., -7, -5, -3, -2, ...$


n represents the number of people.  The probability is that none of these people have a birthday on the same day.  Neglect people that are born on 29 February.  What should n be so that the probability is less than $\frac{1}{2}$  so the probability should be something like this:  $\frac{365Pn}{(365)^n}$ = 0.5  but how to get n?

I found on this website  proof that the probability of two people in a room having the same birthday equates to 50% when when there are 23 people in the room  The only thing is, the explanation is too complicated for the average Middle School student to comprehend. So, my question is, is there any simplifies explanation of how this works? I tried Wikipedia but the explanations were even more complicated.  Thanks!


i have seen some analogies of spin using playing cards but i am struggling to grasp the concept due to this making no sense in terms of playing cards

I often hear about subatomic particles having a property called "spin" but also that it doesn't actually relate to spinning about an axis like you would think. Which particles have spin? What does spin mean if not an actual spinning motion?


I’m an Australian permanent resident with an expired British passport which includes my visa to return to Australia after travelling overseas. When I renew my passport, is the visa automatically renewed or do I do that separately?

I was granted a visa to Australia few months ago. I’d like to travel to Australia in few days. However, I’ve just renewed my passport and I don’t have enough time to inform them about my passport renewal. Can I travel to Australia by carrying both my old and my new passports?


I am solving an algebraic equation: $x+y+z=xyz$ for $x, y,z\in\mathbb{N}$ I want to find out what $x, y, z$ are and if  there are more possibilities. By guessing I found out that $x,y,z=1,2,3$ but I want to solve it solve it algebraically. I solved the Equation for $x$: $$ x+y+z=xyz $$ $$ \text{Subtract } xyz $$ $$ x+y+z-xyz=0 $$ $$ \text{Add }{-y-z} $$ $$ x-xyz=-y-z $$ $$ \text{Factor out }x $$ $$ x(-yz+1)=-y-z $$ $$ \text{Divide by }{-yz+1} $$ $$ \frac{x(-yz+1)}{-yz+1}=\frac{-y-z}{-yz+1} $$ $$ x=\frac{-y-z}{-yz+1} $$ $$ \text{Take Factor as }{-1} $$ $$ x=\frac{-1(-y-z)}{-1(-yz+1)} $$ $$ x=\frac{y+z}{yz-1} $$ But I can't go any further by replacing $x$: $$ \frac{y+z}{yz-1}+y+z=\left(\frac{y+z}{yz-1}\right)yz $$ Can please you help me?

Let $x,y,z$ be 3 co-prime integers. Show that the only nontrivial solutions of: $$x+y+z=xyz$$ are only the permutations of $(x,y,z)=\pm(1,2,3)$


So I need to evaluate $$\lim_{n\to\infty}n\sin(2\pi en!)$$ And yes, I know it was discussed  and similar limit was discussed , but I didn't feel quite okay with the solutions/hints given in those links so I did it my way. That's what I did: $$\begin{align}\lim_{n\to\infty}n\sin(2\pi en!)&=^{stirling}\lim_{n\to\infty}n\sin\left(2\pi e \sqrt{2\pi n} \left(\frac{n}{e}\right)^n\right)\\ &=\lim_{n\to\infty}n\sin\left((2\pi)^{\frac{3}{2}}e^{1-n}n^{n+\frac{1}{2}}\right)\\ &=^{\{en!\}=\frac{1+O(n^-1)}{n+1}}\lim_{n\to\infty}n\sin\left(\frac{2\pi (1+O(n^{-1})}{n+1}\right)\\ &=^{sin(n^{-1})\sim n^{-1}}\lim_{n\to\infty}\sin\left(\frac{2\pi n (1+O(n^{-1})}{n+1}\right)\\ &=2\pi\end{align}$$ But my professor didn't accept it because we didn't cover Stirling yet and said I need to prove it another way (he also didn't accept the solutions given in the links above). He told me to use the fact that $$\lim_{n\to\infty}n\sin(2\pi en!)=\lim_{n\to\infty}n\sin(2\pi en!-2\pi n)$$ and then using Taylor or something, but this so called "clue" got me nowhere. Any ideas?

I tried and got this   $$e=\sum_{k=0}^\infty\frac{1}{k!}=\lim_{n\to\infty}\sum_{k=0}^n\frac{1}{k!}$$ $$n!\sum_{k=0}^n\frac{1}{k!}=\frac{n!}{0!}+\frac{n!}{1!}+\cdots+\frac{n!}{n!}=m$$ where $m$ is an integer. $$\lim_{n\to\infty}n\sin(2\pi en!)=\lim_{n\to\infty}n\sin\left(2\pi n!\sum_{k=0}^n\frac{1}{k!}\right)=\lim_{n\to\infty}n\sin(2\pi m)=\lim_{n\to\infty}n\cdot0=0$$  Is it correct?


I have a path "/third/party/city of las vegas"   when cd the path I use "/third/party/city of las vegas".  In .profile file I have exported the path to a variable as follows  export clv="/third/party/city of las vegas"   when I try to cd $clv it is throwing an error.  How can I export a path which have spaces in the directory name

Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it?


So I've been running Ubuntu without Windows. I got a Windows 7 live CD and tried to do a Windows 7/Ubuntu dual boot but I couldn't get the boot to load correctly so I decided to go back to just Ubuntu. However now I just have a Ubuntu install and it won't boot. I've tried boot-repair and it still won't boot.    What should I try next?

I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?