This could be a privilege to be given after some amount of reputation. Consider accordingly.  When a user receives a down-vote, without having laid a comment for the reason why, that user -right now- gets a recommendation message to leave down a comment for the reason why. Users may ignore that recommendation and they should be able to. It could be that the reason is obvious, or some other thing, so they should be able to.  However, sometimes the guy or the lady who had given the answer, may not understand for what his or her answer could have been voted down. It should be a natural request to ask for what one had done wrong after having disapproved. If one couldn't figure out the reason himself or herself, and not told about it either, then he or she may never know what he or she should do to improve himself/herself.  Back to the part where we ask for the reason: We should be able to do that in this environment as well, just like we can when we are face to face.  Here is what I am suggesting for things to happen:  ~ After 200 reputation points, users are to be given this privilege. ~ When someone's answer gets voted down, and that other someone who had cast that vote had not left a comment, then the one who gave the answer is to be given a button to use for asking for why. ~ With the use of that button, the one(s) who voted down the answer are to get informed about the request of the one who answered the question. ~ For each request that does not get fulfilled within 2 days, the corresponding vote is to get discarded.  After this process, an addition to that would be:  ~ The comment as the reason is to be marked as a reason by a light blue centre-dot behind the comment. ~ Such comments will be official the reason for the corresponding vote, and be referred as a document for further cases like:   In general, this would flourish the quality criticism which could really nicely happen in Stack Overflow, but unfortunately does not happen that so often. People would know where they had been wrong, therefore have the opportunity to improve themselves; and people would act more reasonable, literally, since they will be giving reasons for their actions.  Numbers are not strict, feel free to discuss. This could be extended to questions, if found useful.

Each question in SO keeps a list of the users who voted it down. As we all know, the list is never shown to anyone. Only the down voter can see which questions he down voted.   Sometimes, down voters down vote rather hastily. Thats okay because no one is perfect (except chuck norris). But sometimes, the down voter might have a good reason to down vote but may not leave a reason behind. As a result, the poster is left wondering if his question is stupid/bad or okay. To remedy this situation, I suggest a feature below -   The poster should have a button "request down voters for reason" which can be pushed only once. The down voters in the down voter list get the notification and can choose to respond to it. I feel that this can serve as a polite reminder to those who down vote a question which would seem to be an okay (if not good) question to most people.   Example of question which I feel should have at least 0 votes -    If okay, then this feature can be combined with -    Do you agree to the proposal ?  As an aside, do you agree that the SO question above should not get negative points ?


Is there a way to predict a decay chain? Let's say I have U-238 and want to find out its decay chain, is there a way to do that without looking it up? Thanks in advance.

I know there are tables of decay chain of radioactive elements. Is there a way to predict the whole chain from the first radioactive element?


I'm new to SQL server and need your advice.  I have a database that shows 188GB as the size in the database properties window.  When I take a backup of the database, that backup file is only 65GB.  The database properties window still shows the database itself is 188GB.  Why is there a difference in the size of the backup compared to the actual database?  I'm not using backup compression.

I just took a backup of a SQL Server database.  The MDF and LDF files together total around 29 GB, but the .bak file was only 23 GB, about 20% smaller.  My first guess when one version of a set of data is smaller than another version containing the same data would be data compression, but compression usually yields a much better compression ratio than 20%, especially for highly-ordered data (such as database tables.) Also, compressed data can't easily be compressed further, but I know that .bak files can be compressed.  So if the data isn't being compressed, and nothing's being discarded, (because the whole point of making a backup is to be able to restore it to an identical state afterwards,) then what's that 20% that's unaccounted for?


I have a database with millions of record and I have to search and show the records based on search key. I am using PHP to communicate with MySQL and I can do it in traditional way but it's not a optimized way to do that.  I want to this with MySQL procedures, is this a optimized way? If yes then how we can create procedure and how to use in PHP code? I am using this code to create:  DELIMITER $$ DROP PROCEDURE IF EXISTS `getExerciseForSearchKey` $$ CREATE PROCEDURE `getExerciseForSearchKey`(IN searchText varchar(255),OUT result varchar) BEGIN SELECT * FROM exercisetemplate WHERE key like '%searchKey%'; END $$  DELIMITER ;

The question is a fairly open one. I've been using Stored Procs with MS SQLServer for some time with classic ASP and ASP.net and love them, lots.  I have a small hobby project I'm working on and for various reasons have gone the LAMP route. Any hints/tricks/traps or good starting points to get into using stored procedures with MySQL and PHP5? My version of MySQL supports Stored Procedures.


I have a laptop with Linux Mint installed. I had a power outage, and currently, it cannot boot - it shows grub rescue when booting.  I don't mind formatting and re-installing the system, but there are a couple of files which I'd like to recover.  I ran Boot-Info from a live USB, but it didn't help. Here are the logs:   Can you please help me with this? I'm not familiar enough with Linux to understand much from the logs.

My hard drive is a mess and I want to reformat it and do a fresh install of 16.04. My problem is I only have access to the HDD via 16.04 on a USB stick and although I can navigate to the various folders, nothing I do allows me to copy to an external hard drive. The folders are not encrypted. I also have a small swap partition - I would like to preserve the data on that too if possible.  Here's a listing of the home directories on the drive:  ubuntu@ubuntu:/$ ls -l /media/*/*/home /media/ubuntu/0e228f65-dac7-435f-828b-1eb1a6c3f29a/home: total 4 drwxr-xr-x 46 1000 1000 4096 Dec 21  2015 simon  /media/ubuntu/db79a6d1-7c6c-4d8c-822b-ba6ccd1ddecd/home: total 4 drwxr-xr-x 27 1000 1000 4096 Apr 17  2014 simon  /media/ubuntu/ebe2a6ba-9cb5-4279-8352-5082b8dd4d5e/home: total 4 drwxr-xr-x 39 1000 1000 4096 Aug  3 14:21 simon


The Winter Bash icon is missing as with the hat's I earned. I have earned two hats, including one which come with the silver badge, It was there, and I was using it also. But now when I log in it's not there. Any help would be appreciated.    As you can see above there is not a hat or Winter Bash icon.  I am using macOS v10.13 (High Sierra) and my browser is Chrome version 63.0.3239.84 (official build) (64-bit).

We just noticed on the Tavern on the Meta, that hats seem to have vanished on chat.  They also seem to be gone on regular chat, and I don't see the snowflake on Meta Stack Exchange some of the time (it's randomly appearing by the looks of things then vanishing).  I usually use Vivaldi, but the same issue on Firefox (I'm on 57 or thereabouts).  I suppose we can blame load, or hats..  or is it a hat hating grinch?      Totally glitched grinched I guess


What do we see if a single ray of white light falls in to our eyes ?  Doesn't it undergo dispersion ?

Fairly straightforward question. If not, why not?  I suspect that if they do, it is not perceived due to the regions of highest dispersion being in one's region of lowest visual acuity.


$$\frac{3}{|z_2-z_3|} = \frac{4}{|z_3-z_1|}=\frac{5}{|z_1-z_2|}$$ Find the value of $$\frac{9}{|z_2-z_3|}+\frac{16}{|z_3-z_1|}+\frac{25}{|z_1-z_2|}$$   Let The given equality be equal to some value k Then $$9=k^2|z_2-z_3|^2$$ and so on  Replacing these values  $$k^2[|z_2-z_3|+|z_3-z_1|+|z_1-z_2|]$$ How should I solve further? The minimum value can be calculated to be zero, but the question is asking for the actual value.

If $\dfrac{a}{|z_2-z_3|}=\dfrac{b}{|z_3-z_1|}=\dfrac{c}{|z_1-z_2|}$, then why is $\dfrac{a^2}{z_2-z_3}+\dfrac{b^2}{z_3-z_1}+\dfrac{c^2}{z_1-z_2}=0$?   This is a complex number property given in my book but the derivation is not given. How do I get this result? I refer to the chapter complex numbers of the book 39 years chapterwise topicwise solved papers by Arihant.


I have ubuntu 19.10 on my computer and I installed google-chrome as default browser. I noticed that chrome not display emoji on different sites.  I tried reinstall, remove all catalog google-chrome from .config directory. Nothing from these actions didn't help. I also noticed that on firefox this problem not existing. Below I put images which describe the problem.

I've upgraded from 17.10 to 18.04 and was hoping to have better emoji support. The results are that Chrome (66) is still using the old black and white emoji font, and Firefox (59) is managing to show some color emoji but not others. I took some advice to install the font EmojiOne but that didn't seem to help 😓  Screenshots from the emoji demo page at  :  Chrome:   Firefox:


Please help me out the number of a car. Robbers entered our city late at night to steal in 3 cars including my car. High value coins and other items were taken away. The neighbor's camera filmed the robbers' vehicle. See picture. Help me from this image to extract the serial number of the vehicle. I am stuck. Thank you.  Video Link:

Recently, we had a problem with people doing donuts in our parking lot. We have the cameras in place but the night vision camera couldn’t see the license plate because of the lights that illuminate the plate. It looked like a blank, white rectangle where the license plate should be.   Is there anything I can do in Photoshop or something of the sort in order to get the plate numbers?


I have a new Mac Mini (MacMini6,1 late 2012) that I would like to install Ubuntu Server 13.04 (ubuntu-13.04-server-amd64+mac.iso) on. But it seems like Ubuntu Server isn't able to detect my network interface, because I get the message:     No network interfaces detected   How can I fix this issue? Is there any module or driver that I can add for this?    I have now tried to install Ubuntu Server with the build-essentials package and downloaded source to the tg3-driver as suggested in the answers. But when compiling (with the make command) I get errors:  ... cc1: some warnings being treated as errors make[2]: *** [/home/jonas/tg3-3.129d/tg3.o] Error 1 make[1]: *** [_module_/home/jonas/tg3-3.129d] Error 2 make[1]: Leaving directory `/usr/src/linux-headers-3.8.0-19-generic` make: *** [default] Error 2   Any suggestions?

The said network adapter is not recognized in 13.04. In 12.04 and 12.10 I had used the driver proposed from broadcom download site, configured as dkms package it was always updated.  On the 3.8.x kernels this provided kernel driver from broadcom does not compile anymore - and the distribution provided tg3 drivers does not recognize the ethernet adapter - even though it is a newer version.  ~$ modinfo /lib/modules/3.8.0-19 generic/kernel/drivers/net/ethernet/broadcom/tg3.ko | grep -i version version:        3.128 srcversion:     D737202366709FE01964BF0 vermagic:       3.8.0-19-generic SMP mod_unload modversions    Here the working version on kernel 3.5.x using dkms  ~$ modinfo /lib/modules/3.5.0-25-generic/updates/dkms/tg3.ko | grep version version:        3.124c srcversion:     D01ED9A7BF2C3956E212A63 vermagic:       3.5.0-25-generic SMP mod_unload modversions    The Network card:  ~$ lspci -nn | grep 0200 01:00.0 Ethernet controller [0200]: Broadcom Corporation NetXtreme BCM57766 Gigabit Ethernet PCIe [14e4:1686] (rev 01)   As found on the i7 Mac Mini 6,2.  Anyone knows where I can get a kernel that recognizes that ethernet device ? That chip is supported somehow ... And - the 3.8.x kernel is way better on the HD4000 chip - reason I use it.  Note - to get the WiFi working, just make sure you load the b43 driver at boot (/etc/modules). At least then you have Network connectivity.


I'm using FF 3.5 and have popup blocker enabled. But I'm still getting popups. I'm guessing their flash based. The real annoyance is that they cover the text of the website and (in some cases like the one below) don't have a "close" button.  An example of a popup that appears and annoying covers the text.

For many years I have blocked popup ads with AdBlock Plus.  But it seems more and more these past couple months there is a "new" kind of popup overtaking the web.  They are javascript based "modal" popups which ABP is powerless over.  See attached for an example.  Is there a way to kill these ads without breaking the functionality of anything I need?


The congruence equation $a\equiv b \pmod n \implies \exists k \in \mathbb{Z}, a -b = kn.$ Taking the i-th power of both sides : $(a -b)^i = k^in^i$.   $(a-b)(a-b)^{i-1}=k^in^i$. $n\mid (a-b), (a-b) \mid (a-b)^i \implies n\mid (a-b)^i \implies \exists m \in \mathbb {Z}, (a-b)^i = mn$.  But, my proof is incomplete, as it does not show still that $a^i - b^i = kn$.    All the comments and answer have ignored the fact that how to get the term $a^i - b^i$ in the first place.  It seems that all have taken the approach to simply take the $a^i- b^i=kn$ as a new equality, not derived from the original one. Just it uses the property of $n \mid (a-b)$ of the original one.

I did some mathematical induction problems on divisibility   $9^n$ $-$ $2^n$ is divisible by 7. $4^n$ $-$ $1$ is divisible by 3. $9^n$ $-$ $4^n$ is divisible by 5.   Can these be generalized as $a^n$ $-$ $b^n$$ = (a-b)N$, where N is an integer? But why is $a^n$ $-$ $b^n$$ = (a-b)N$ ?  I also see that $6^n$ $- 5n + 4$ is divisible by $5$ which is $6-5+4$ and $7^n$$+3n + 8$ is divisible by $9$ which is $7+3+8=18=9\cdot2$.  Are they just a coincidence or is there a theory behind?  Is it about modular arithmetic?


I left an Indian cuisine frozen entrée out and I left for two weeks. Will I come home to maggots? I heard Frozen foods can't produce maggots. Please help!

If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more?


I would appreciate any help to solve this issue. I am building a report and would like to display the date of birth in the following format e.g: 7Yrs, 5Mths, 3Days based on the given date of birth stored in the database. On my query, I noticed that the calculation applied is giving me wrong results. Here is the query: With cte As  (   SELECT DOB FROM myTableName   where ID ='60113012' )  SELECT CAST(DATEDIFF(yy, DOB, getdate()) AS varchar(4)) +' Yrs '+        CAST(DATEDIFF(mm, DATEADD(yy, DATEDIFF(yy, DOB, getdate()), DOB), getdate())  AS varchar(2)) +' Mths '+        CAST(DATEDIFF(dd, DATEADD(mm, DATEDIFF(mm, DATEADD(yy, DATEDIFF(yy, DOB, getdate()), DOB), getdate()),         DATEADD(yy, DATEDIFF(yy, DOB, getdate()), DOB)), getdate()) AS varchar(2)) +' Days' AS result   FROM cte  Result:  The issue is that I'm getting the wrong results. some of the results have * instead of the number indicating the days. Also, some have a negative before the number of days. Examples: DOB                       Results 2015-08-30 00:00:00.000 5 Yrs -1 Mths * Days 2016-09-02 00:00:00.000 4 Yrs -2 Mths 12 Days 2016-03-18 00:00:00.000 4 Yrs 4 Mths -4 Days 2015-03-21 00:00:00.000 5 Yrs 4 Mths -7 Days

What would be the best way to calculate someone's age in years, months, and days in T-SQL (SQL Server 2000)?  The datediff function doesn't handle year boundaries well, plus getting the months and days separate will be a bear.  I know I can do it on the client side relatively easily, but I'd like to have it done in my .


Came across the identity, interested in the same observation from others and how have others arrive at it:  $$\arctan(6/10)+\arctan(1/4) = \frac{\pi}4$$  thank you in advance. Probably trivial. I took the long way home.

In the arctangent formula, we have that:  $$\arctan{u}+\arctan{v}=\arctan\left(\frac{u+v}{1-uv}\right)$$  however, only for $uv<1$. My question is: where does this condition come from? The situation is obvious for $uv=1$, but why the inequality?  One of the possibilities I considered was as following: the arctangent addition formula is derived from the formula:  $$\tan\left(\alpha+\beta\right)=\frac{\tan{\alpha}+\tan{\beta}}{1-\tan{\alpha}\tan{\beta}}.$$  Hence, if we put $u=\tan{\alpha}$ and $v=\tan{\beta}$ (which we do in order to obtain the arctangent addition formula from the one above), the condition that $uv<1$ would mean $\tan\alpha\tan\beta<1$, which, in turn, would imply (thought I am NOT sure about this), that $-\pi/2<\alpha+\beta<\pi/2$, i.e. that we have to stay in the same period of tangent.  However, even if the above were true, I still do not see why we have to stay in the same period of tangent for the formula for $\tan(\alpha+\beta)$ to hold. I would be thankful for a thorough explanation.


In order to redirect both stdout and stderr to a file: curl 'https://example.com' > myfile 2>&1  This works correctly, but why must the redirection of standard error to standard output be at the very end? Why can't it be: curl 'https://example.com' 2>&1 > myfile  I don't understand why this alternative does not work; it does not redirect stderr to the file. Reading from left to right: "download the web page, redirect stderr to stdout, and redirect stdout to a file", but this is apparently not how Bash interprets the commands. Bash expects 2>&1 to come last. Why must the 2>&1 come last?

If several redirections are used together, does changing their order make difference?  How shall one understand the meaning of their order? Is the chained channel of redirections built as reading the redirections from left to right, or from right to left?  For example  command 2>&1 > somefile  command > somefile 2>&1   Thanks and regards!


I accidentally messed up my $PATH. I Tried to follow the instructions from the previous similar questions but I keep having the same problem When I type:  echo$ PATH,  I get the following response: /Library/Frameworks/Python.framework/Versions/2.7/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin . Do you know how i can reset the PATH?  The operating system is OS X El Capitan. Thank you so much

I was trying to add something to $PATH and it went totally wrong.  I now can't run any commands such as ls.  I've looked at this   and used the following lines:  PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin PATH=$PATH:~/bin   These lines fix the problem temorarily; however, when I restart terminal it seems to forget these changes.  How do I permanently reset my $PATH?  I'm running the most recent version of Mountain Lion.


I try so many time for more than 1hr to create and account in Ubuntu One to use only the feature Sync Between Computers but is impossible to read the security code and always get the error Wrong Captcha Solution. Is there is another solution to sync apps between computers beside Ubuntu One? even if I have to pay for it. Is so impossible to create and simple account.

Since Ubuntu one is no longer it appears that Sync between computers no longer works.  Is there a new method to do this?  I'd like to sync the apps from one machine to another.


I log into my SE account with SE. And I read that they won't be adding support for 2FA. But there's no article informing a work around for the people who signed up with SE in the first place.  First I thought I could  with a site supporting 2FA and remove the SE login. But there's no way to remove the first login.  there was a way to remove logins but it's not working.  So my last hope is I can create another SE account and sign up with a site supporting 2FA, and then follow the  and hope that they leave the second account's login as the only one (something I'm not sure will happen).  Thanks in advance for any help you can give me. I hope I'm not seeing something and there's a much more simpler solution.

I have two OpenID accounts. So what I want to do is delete or remove my private email from the StackExchange OpenId, but the problem is I can't find the remove, delete or deactivate button?  I want to remove my private email from OpenID because I only use that email for my family, friends and love ones.


i have a loop checking the value of a variable and when i update the variable "i" to match one of the if statements nothing happens, anyone know why this is happening or how to fix it? i have it printing the "i" variable to console so i can see it changing but it wont activate one of the if statements   code  package window;  import java.awt.EventQueue;  import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.border.EmptyBorder; import javax.swing.JButton;  import java.awt.event.ActionListener; import java.awt.event.ActionEvent;  import javax.swing.JTextArea; import javax.swing.JTextField;  public class Gui extends JFrame {  public JPanel contentPane; public static JTextField input; public static JButton send; public static JTextArea console; public static JTextArea invintory; public static JTextArea stats;  /**  * Launch the application.  */    /**  * Create the frame.  */ public Gui() {     //variables      int Gold = 20;     int Health = 100;     int MaxHealth = 100;       //variables end     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     setBounds(100, 100, 450, 300);     contentPane = new JPanel();     contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));     setContentPane(contentPane);     contentPane.setLayout(null);      console = new JTextArea();     console.setEditable(false);     console.setBounds(10, 11, 281, 214);     contentPane.add(console);      input = new JTextField();     input.setBounds(10, 236, 281, 20);     contentPane.add(input);     input.setColumns(10);      stats = new JTextArea();     stats.setEditable(false);     stats.setBounds(301, 11, 123, 53);     contentPane.add(stats);      invintory = new JTextArea();     invintory.setEditable(false);     invintory.setBounds(301, 75, 128, 137);     contentPane.add(invintory);      send = new JButton("Send");        send.setBounds(301, 224, 128, 32);     contentPane.add(send);      stats.append("Health: " + Health + "/" + MaxHealth + "\n");     stats.append("Gold: " + Gold);      }  public static void game (JButton send, JTextArea console, JTextArea stats, JTextArea invintory, JTextField input) {      //variables      int Gold = 20;     int Health = 100;     int MaxHealth = 100;         //start     //START     //START     //START     //START     while (true) {           input.setText("");         String i = "";          send.addActionListener(new ActionListener() {                 public void actionPerformed(ActionEvent arg0) {                     String i = input.getText();                     System.out.println("input is " + i);                     stats.setText("");                     stats.append("Health: " + Health + "/" + MaxHealth + "\n");                     stats.append("Gold: " + Gold);                 }             });         console.append("You wake up open feild, with vast amounts of wheet in every direction\n");         console.append("There is a path going in either direction what do you want to do\n");         console.append("\t1. Go left.\n");         console.append("\t2. Go right.\n");          while (i == "") {         if (i == "1") {             console.append("1\n");             break;         }         else if (i == "2") {             console.append("2\n");             break;         }         else {          }         }        }     //END     //END     //END     //END     }  public static void main(String[] args) {             try {                 Gui frame = new Gui();                 frame.setVisible(true);                 Gui.game(send, console, stats, invintory, input);             } catch (Exception e) {                 e.printStackTrace();             }          } }

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


Let's say I have a script:  #!/bin/bash echo "$1" if [[ ! $1 ]]; then     echo "True" fi export ABC="/home/aashish"   ABC is not available after the execution of this script. How can I make that variable persist after the execution as well?

I have multiple Amazon EC2 accounts and want to quickly be able to switch variables, such as $EC2_HOME, using a script.  I have have a shell script set up like this:  #!/bin/sh export EC2_HOME=/home/me/.ec2 echo $EC2_HOME   When I run the script I know that EC2_HOME is set, but I thought that using export would make the variable stick around after the script completed. It does not, as running echo $EC_HOME does not show anything.  I know this must be very rudimentary Linux scripting knowledge, but I don't know it. I tried looking for related questions without luck - so my apologies if this is a duplicate.


I was checking the performance of OPTION(RECOMPILE) and OPTION(FAST n) and their behaviors are surprisingly different. OPTION(FAST n) is much faster then OPTION(RECOMPILE). Does OPTION(FAST n)? create new execution plan every time?

I have done some digging on what the OPTION (FAST XXX) query hint does inside a SELECT statement and I'm still confused about it. According to MSDN:  Specifies that the query is optimized for fast retrieval of the first number_rows. This is a nonnegative integer. After the first number_rows are returned, the query continues execution and produces its full result set.  For me that does not make much sense but basically the query can get the first XXX rows really fast then the rest at normal speed? The Microsoft Dynamics query that got me thinking on this is: select pjproj.project,pjproj.project_desc,pjproj.customer,pjproj.cpnyid from pjproj WITH (NOLOCK) where project like  '%' order by project OPTION(FAST 500)  Can anyone explain exactly what this query hint is doing and its advantage over not using it?


\todo[inline]{   \begin{itemize}   \item aaaa   \item bbbb   \end{itemize}}   I have no problem to use \todo without using itemize inside. So what is the problems here? Thanks!

I'm using todonotes to make notes on my thesis. I'd like to be able to put some dot-points on a couple of the larger notes, like this:  \todo[inline]{   \begin{itemize}     \item blah blah blah   \end{itemize} }   But I get this error message:  ! Argument of \reserved@a has an extra }. <inserted text>             \par l.9 }   Is there anything I can do to get around this, or is it basically not worth trying?


Light obeys the particle wave theory. This has always confused me. I understand the mechanism of the wave according to Maxwell theory. But, I run into problems when I think about the photon. How does it propagate? If I have a single photon moving through space, what does it mean? I mean, surely electric and magnetic fields cant only exist at one point helping each other move forward right? If light is electromagnetic, how is a photon electromagnetic? I don't get it. Or maybe because of the uncertainty principle, and we can approximate the momentum of light (radiation pressure), we have no Idea about its position. So the electric and magnetic field exist over some distance, and this is how electric and magnetic fields interact to push the particle forward?

At the end of this nice video (), she says that  is a chain reaction of electric and magnetic fields creating each other so the chain of wave moves forward.  I wonder where the  is in this explanation. What is the relation between electromagnetic wave and photon?


I recently ran the offered system update for my Ubuntu 18.04 installation.  Everything appeared to go well even if it did take over an hour and I was quite happy whit how it all turned out.  However I've just noticed that the calendar that I was running in Thunderbird 60.20.1  has disappeared.  This is a real pain as I use the calendar a lot and have a lot of reminders set in it.  Can anyone advise; Has the calendar just been de-activated and can be re-activated?  If so how do I do it?  Or  Have I lost everything and have to start again?

After completing an Ubuntu automatic software update (15 Oct 2018) that included Thunderbird 60.2.1 the Lightning calendar is now missing.  When I click on Thunderbird's Add-On tab to see if there's an update for Lightning I'm told that all the versions of Lightning available there are not compatible with the updated Thunderbird release. All my calendar data is no longer available to me - HELP!!


$1! + 2! + 3!+\cdots + 99! + 100!$  I am not getting any idea on how to solve this problem. I know that modular arithmetic should be used but not getting how to start off with the solution. Please give me some hint on how to approach this question. Thanks in advance.

What is the remainder when $$1! + 2! + 3! +\cdots+ 1000!$$ is divided by $12$.  I have tried to find the answer using the Binomial Theorem but that doesn't help. How will we do this?  Please help.


Prove that $390\mid n^{13}-n$ for all $n\in\mathbb Z$   Attempt:  $$390=2\times3\times5\times13$$  Fermat theorem: $a^p\equiv a\pmod p$, here:  $$n^{13}\equiv n \pmod{13}$$  So $\color{red}{13}\mid n^{13}-n$ but what can I say about $\color{red}{390}$?

Show that $2730\mid n^{13}-n,\;\;\forall n\in\mathbb{N}$   I tried, $2730=13\cdot5\cdot7\cdot3\cdot2$  We have $13\mid n^{13}-n$, by Fermat's Little Theorem.  We have $2\mid n^{13}-n$, by if $n$ even then $n^{13}-n$ too is even; if $n$ is odd $n^{13}-n$ is odd.  And the numbers $5$ and $7$, how to proceed?


Do you have any solution for this?  I know I can hide labels via template.php but how to add placeholders to some inputs?

Is there a way to convert a regular form and add placeholders with a module, or should this be done with a form template or with jQuery?


I want to use the integral test to show that $ \sum_{n=3}^{\infty} {1 \over {n\cdot \log{n} \cdot \log{\log {n}}}} $ diverges.  First, I let $ f(x) = {1 \over {x\cdot \log{x} \cdot \log{\log {x}}}} $  I have learned that in order to use the Integral test, $f(x)$ must be continuous, positive, and decreasing at the interval $ [1,\infty) $  However, when I drew the graph of $f(x)$ using an online graphing calculator, the graph only seemed to be satisfying the three conditions of the Integral test when $ x \geq 10 $, or the interval $ [10, \infty) $  Doesn't that mean that I cannot use the Integral test? Other than that, I was also confused on why the series starts from n = 3 when the series is also defined a value at n = 2. (although negative, like at n = 3)

I'm being asked to determine if $\displaystyle\sum\limits_{n=3}^\infty \frac1{n (\ln n)\ln(\ln n)}$ converges. So, using Cauchy's Condensation Test, I reduced the problem to one of determining the convergence of $\displaystyle\sum\limits_{n=3}^\infty\frac 1{n\ln (n\ln 2)}$. Am I on the right path, and how do I proceed from here?


when I am using subfiles in my tex document: \subfile{./chapter-2020-02/chapter-2020-02}  when the subfile using figure like this: \begin{figure}[htbp]     \centering     \includegraphics[scale=0.3]{mavenauthpassword}     \caption{Maven}     \label{fig:mavenauthpassword} \end{figure}  shows this error: ! LaTeX Error: File `mavenauthpassword.tex' not found.  what should I do to using figure correctly when using subfiles in latex document?

Now I am using subfile to compile document independent, I want to insert a picture in the sub document like this: \documentclass[../../../dolphin-book-2020.tex]{subfiles}  \begin{document}  \subsection{GitHub Slow}  balabalabala.......   \begin{figure}[htbp]     \centering     \includegraphics[scale=0.2]{githubspeedup}     \caption{GitHub Speed Up}     \label{fig:githubspeedup} \end{figure}   \end{document}  when I compile using this command in macOS Catalina 10.15 :  /Library/TeX/texbin/latexmk -pdfxe -pvc -xelatex -interaction=nonstopmode ./github-slow.tex  show this error: (/usr/local/texlive/2020/texmf-dist/tex/latex/listings/lstlang1.sty) (/usr/local/texlive/2020/texmf-dist/tex/latex/listings/lstlang1.sty)  Package fontspec Warning: Font "FandolFang-Regular" does not contain requested (fontspec)                Script "CJK".   ! LaTeX Error: File `githubspeedup' not found.  See the LaTeX manual or LaTeX Companion for explanation. Type  H <return>  for immediate help.  ...  l.31 ^^I\includegraphics[scale=0.2]{githubspeedup}  [1] (./github-slow.aux)  LaTeX Font Warning: Some font shapes were not available, defaults substituted.   LaTeX Warning: Label(s) may have changed. Rerun to get cross-references right.   ) (see the transcript file for additional information) Output written on github-slow.xdv (1 page, 28900 bytes). Transcript written on github-slow.log. === TeX engine is 'XeTeX' Latexmk: Index file 'github-slow.idx' was written Latexmk: Missing input file: 'githubspeedup' from line   '! LaTeX Error: File `githubspeedup' not found.' Latexmk: References changed. Latexmk: Log file says output to 'github-slow.xdv' Latexmk: Errors, so I did not complete making targets Latexmk: Failure to make the files correctly     ==> You will need to change a source file before I do another run <== Collected error summary (may duplicate other messages):   xelatex: Command for 'xelatex' gave return code 1       Refer to 'github-slow.log' for details  === Watching for updated files. Use ctrl/C to stop ... ^CLatexmk: User typed ctrl/C or ctrl/break.  I'll finish. Collected error summary (may duplicate other messages):   xelatex: Command for 'xelatex' gave return code 1       Refer to 'github-slow.log' for details Latexmk: Use the -f option to force complete processing,  unless error was exceeding maximum runs, or warnings treated as errors.  what should I do to make it work? I have already added picture path in the main file dolphin-book-2020.tex like this(all the picture store in the folder and no picture store in sub folder): \graphicspath{{./Pictures/}}  and this is the file structure:  I have tried define picture path in dolphin-book-2020.tex like this: \graphicspath{{../../../Pictures/}{../../Pictures/}{../Pictures/}{./Pictures/}}   this is the folder nested structure:  I also tried to write all possible path of picture: \graphicspath{     {Pictures/}     {../../../Pictures/}     {../../Pictures/}     {image/}     {/Users/dolphin/Documents/GitHub/dolphin-book-2020/Pictures} }  still could not found file.


I'm writing a program that adds itself to the startup items using the following:  RegistryKey reg = Registry.CurrentUser.OpenSubKey(     "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run", true); reg.SetValue("Application", Application.ExecutablePath.ToString());   I want to give the user a simple option to remove the program from the startup items. Is there a way to do this?

I can get/set registry values using the Microsoft.Win32.Registry class. For example,  Microsoft.Win32.Registry.SetValue(     @"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run",     "MyApp",      Application.ExecutablePath);   But I can't delete any value. How do I delete a registry value?


public class Main{ . . . Class class = new Class(); class.method(class.variableFromAnotherClass); sysout(class.variableFromAnotherClass) }  public class Class{ Int variableFromAnotherClass=0;  method(int var){     var=1;     } }   Output:  0   Im dealing with a situation similar to the one above except with more variables in my version of "Class". My issue is that the method within "Class" does nothing to the variable being passed through. Why does this happen? Is it because the variable being passed through already belongs to the class? Any suggestions on What should I do to solve this problem?

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?


According to this website:        The first letter indicates the file type: f means file and d means directory. But in my case I've an l. What's the meaning of this l? In my case, the file is actually a directory too.   Also some entries do not have any file type, i.e. they have a leading dash -. Does this mean that the OS does not recognise the file type?

The ls -al command shows the following output;  -rwxrw-r--    10    root   root 2048    Jan 13 07:11 afile.exe   What are all the fields in the preceding display?


Clicking the blog link in the header on any meta currently takes you to https://blog.stackoverflow.com/?blt=1  which didn't display the new blog post for a non-trivial amount of time. You had to remove the blt parameter to actually see . Assuming it was a caching issue, shouldn't the cache for both routes be refreshed when a new blog entry is posted? Likewise, links to new posts in the Community Bulletin can have a similar problem, leading to erroneous 404s like the one shown below:

Stack Exchange blog is showing me the mobile site and won't let me exit on Chrome 21. Could someone take a look? Thanks. Edit I noticed it was with the special query string, that I can't exit it.


we can say 4 is the number you get when you add 1 to itself 4 times. Likewise, 5 is the number we get when we add 1 to itself 5 times.  Now, let's just say 4 = 5. It would have to be the case that 4-5 = 0, however, that would imply 1 = 0. Unfortunately, one of the rules for a ring is that you cannot have 1 = 0, therefore 4 cannot equal 5 in any ring with unity. but I found a calculation.    Relevant snippet  \begin{eqnarray} 2+2&=&4+\frac{9}{2}-\frac{9}{2}\\&=&\sqrt{(4-\frac{9}{2})^2}+\frac{9}{2}\\&=&\sqrt{16-36+(\frac{9}{2})^2}+\frac{9}{2}\\&=&\sqrt{-20+(\frac{9}{2})^2}+\frac{9}{2}\\&=&\sqrt{25-45+(\frac{9}{2})^2}+\frac{9}{2}\\&=&\sqrt{(5-\frac{9}{2})^2}+\frac{9}{2}\\&=&5-\frac{9}{2}+\frac{9}{2}\\&=&5 \end{eqnarray}  Yes, I know that this is not possible but the way it is solved seems pretty much correct to me. That makes me curious that is it somehow possible anyway ?

$$\begin{align} 2+2 &= 4 - \frac92 +\frac92\\ &= \sqrt{\left(4-\frac92\right)^2} +\frac92\\ &= \sqrt{16 -2\times4\times\frac92 +\left(\frac92\right)^2} + \frac92\\ &= \sqrt{16 -36 + \left(\frac92\right)^2} +\frac92\\ &= \sqrt {-20 +\left(\frac92\right)^2} + \frac92\\ &= \sqrt{25-45 +\left(\frac92\right)^2} +\frac92\\ &= \sqrt {5^2 -2\times5\times\frac92 + \left(\frac92\right) ^2} + \frac92\\ &= \sqrt {\left(5-\frac92\right)^2} +\frac92\\ &= 5 + \frac92 - \frac92 \\ &= 5\end{align}$$  Where did I go wrong


Say, I have custom kernel from my distribution, how could I get list of all options the kernel was build with?  It's possible to get them by reading config file from kernel package from vendor's repo, but is there any other way? I mean ways to get that information form the kernel itself, maybe from procfs?

I currently run Angstrom Linux 2.6.32. I intend to upgrade linux kernel from 2.6.32 to 3.0.7. For this reason, I had to configure kernel 3.0.7 running make menuconfig.  Now, I want to compare the new kernel configuration with the previous, but I can't find kernel 3.0.7 configuration file. Any ideas?


I have created a generic swapping algorithm. In order to for this an array is required and the elements are swapped using integer indices.   I have created a JUnit test class for this and cannot figure out what to use instead of assertArrayEquals if the output should be an error.   Here is my attempt:  @Test public void testNull() {     GenericMethods gm = new GenericMethods();     String names[] = null;     Error err = null;     //String expectedOutput[] = { "Hugh", "Simon", "Ebrahim", "Diane", "Paula", "Andrew" };     assertArrayEquals(gm.swap(names, 1, 5), (err)); }   Here is the Generic swap method used  package genericMethods;  import java.util.Arrays;  public class GenericMethods {      public static <T> T[] swap(T[] names, int index1, int index2) {          if(names == null){              return null; //This will return nothing if nothing has been selected         }           if ((index1 >= 0 && index1 < names.length) && (index2 >= 0 && index2 < names.length)) {              T string = names[index1];             names[index1] = names[index2];             names[index2] = string; //Will check if a valid name has been selected         }          return names;     }      public static void main(String[] args) {         String[] names = new String[] { "Hugh", "Andrew", "Ebrahim", "Diane", "Paula", "Simon" };         swap(names, 1, 5); //will swap Hugh with Simon      } }

How can I use JUnit4 idiomatically to test that some code throws an exception?  While I can certainly do something like this:  @Test public void testFooThrowsIndexOutOfBoundsException() {   boolean thrown = false;    try {     foo.doStuff();   } catch (IndexOutOfBoundsException e) {     thrown = true;   }    assertTrue(thrown); }   I recall that there is an annotation or an Assert.xyz or something that is far less kludgy and far more in-the-spirit of JUnit for these sorts of situations.


I have installed Ubuntu 20.04 Microsoft Store on Windows 10 version 2004 and I want to experience the GUI of Ubuntu instead of using shell.  How can I install GUI for Ubuntu app?

I searched around, and currently there are two methods suggested; installing an enhancement for Windows Subsystem for Linux and installing an XServer.  I want to know which method is the most hassle-free (easy to install AND to use), and which one is less memory-heavy.  I just want Synaptic and CMake. Why couldn't that be a builtin feature?


I work at an e-commerce based business in a 16k warehouse. The only available ISP solution is AT&T, with each 6Mb/1.5Mb line costing $50 and fiber optic being an option for $800/mo at 20Mb/20Mb.  Around 15 clients are wired throughout the offices, and another 10 or so exist wirelessly.  I know very little about the stack as it was setup before I arrived, but I am very aware of the real problem we have: it's slow. I don't know if it is download (SpeedTest shows 18Mb down), upload (I was told you can only combine download speeds, not uploading speeds, so SpeedTest shows 1.5Mb) or latency (SpeedTest does not show anything abnormal).  We are using a PepLink to load balance the 3 lines into one solution, but I fear it may be set up incorrectly. I don't know how else to explain why the lag that exists is randomly occurring.  What are common solutions here?  Any help is appreciated. Thanks!


I am making a correlation matrix with booktabs. However, the toprule and similar commands do not extend past the first column when also using \usepackage{xltabular}. I tried to remove the xltabular package and this does indeed fix the problem but I cannot realistically forego this package in my project. How do I fix this? PS: I am using Overleaf, so there is no issue with packages being not up-to-date in Miktex. \documentclass{article} \usepackage[utf8]{inputenc}  \usepackage{booktabs} \usepackage{xltabular}  \begin{document} \begin{table}[ht]         \centering         \caption{Correlation matrix}         \label{tab:mwe_table}         \begin{tabular}{lrrrrrrr}             \toprule                 & A     & B        & C                & D            & E        & F            & G \\              \midrule             A   &          & 0.14     & 0.07             & 0.15         & -0.23    & 0.36         & 0.20 \\              B   & 0.14     &          & 0.07             & 0.71         & -0.45 & 0.69         & -0.09 \\              C   & 0.07     & 0.07     &                  & 0.11         & 0.19     & 0.02         & -0.09 \\              D   & 0.15  & 0.71     & 0.11             &              & -0.02 & 0.64         & 0.18  \\              E   & -0.23 & -0.45 & 0.19             & -0.02     &          & -0.40     & 0.13  \\              F     & 0.36     & 0.69  & 0.02             & 0.64         & -0.40 &              & -0.02 \\              G     & 0.20     & -0.09 & -0.09         & 0.18         & 0.13     & -0.02     &  \\              \bottomrule         \end{tabular}     \end{table} \end{document}

I want to have a page-filling and -breaking longtable, so I decided to try xltabular. Unfortunately xltabular seems to screw up the booktabs rules in the normal tabular environments, see:  \documentclass{article} \usepackage{booktabs, xltabular} \usepackage[active,tightpage]{preview} \PreviewEnvironment{tabular} \begin{document} \begin{tabular}{ccc}     \toprule     col1 & col2 & col3 \\     \midrule     row 2: & more and moooooooooooore & test \\     \bottomrule \end{tabular} \end{document}     Not loading xltabular resolves the issue.  Did I miss some package option or some incompatibilities? Is there a better package than xltabular which doesn't break booktabs?  (I am using TeXLive 2019 and compile with lualatex)    EDIT (by Skillmon)  I reduced the bug to the following MWE (which doesn't make much sense on its own), it looks like booktabs tries to be smart detecting something, but fails badly.  \documentclass{article} \usepackage{longtable} \let\xltabular\relax \usepackage{booktabs}  \begin{document} \begin{tabular}{ccc}     \toprule     col1 & col2 & col3 \\     \midrule     row 2: & more and moooooooooooore & test \\     \bottomrule \end{tabular} \end{document}   It seems to suffice that longtable is loaded and \xltabular is defined (even if it's just \relax).


This is a fresh install on UEFI system. I set up 5 partitions on an nvme ssd:   1GB /boot 16MB biosgrub 512MB efi partition 50GB / root 450GB unused partition (for steam)   /home is located in a separate physical drive, also new (no data in it)  After install, when I choose to boot from the nvme, I only see blank screen with blinking underscore. I tried boot-repair from a livecd but it says no internet connection. I tried to turn off internet related functions, and it asks me to add x86 efi repository. I don't know how to do that  I tried to use update-grub but it says no canonical path for /cow. I mounted the efi partition and tried grub-install --efi-directory but it says "can't find disk"  The partitions were created from scratch via ubuntu installer  Not sure what else can be done at this point

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


When I insert an equation in a item, there will be no indent for the next items just like this.    There are some head file included.  \documentclass[conference]{IEEEtran} \IEEEoverridecommandlockouts \usepackage{cite} \usepackage{amsmath,amssymb,amsfonts} \usepackage{algorithmic} \usepackage{graphicx} \usepackage{textcomp}  \usepackage{algorithm}   \usepackage{algpseudocode}   \usepackage{amsmath}   \renewcommand{\algorithmicrequire}{\textbf{Input:}}  % Use Input in the format of Algorithm   \renewcommand{\algorithmicensure}{\textbf{Output:}} % Use Output in the format of Algorithm \def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}} \begin{document}  \begin{itemize} \item \textbf{Support Vector Machine (SVM).} SVMs are a set of supervised learning methods, and a SVM constructs a hyper-plane or set of hyper-planes in a high or infinite dimensional space, which used for classification, regression and outliers detection. Intuitively, a good separation is achieved by the hyper \begin{equation} \[\begin{align} \text{minimize  }& \frac{1}{n}\sum\limits_{i=1}^{n}{{{\zeta }_{i}}+}\lambda  {{\left\| \mathbf{w} \right\|}^{2}} \\  \text{subject to  }& {{y}_{i}}(\mathbf{w}\cdot {{\mathbf{x}}_{i}}-b)\ge 1- {{\zeta }_{i}} \\ & {{\zeta }_{i}}\ge 0,i=1,...,n \\  \end{align}\] \end{equation} where $ \mathbf{x}_i $ is a $ p $-dimensional real vector; $ y_i $ is either  -1 or 1, denoting the different classes respectively, and $ n $ is the  length of a training dataset. $ \mathbf{w} $ is the normal vector to th  hyperplane. For each $ i\in\{1,...,n\} $, a variable $ \zeta_{i}=\text{max} (0,1-y_i(\mathbf{w}\cdot {{\mathbf{x}}_{i}}-b)) $ is introduced and it is the  smallest nonnegative number satisfying {{y}_{i}}(\mathbf{w}\cdot  {{\mathbf{x}}_{i}}-b)\ge 1-{{\zeta }_{i}}. Moreover, $ \lambda $ is a  sufficiently small value yields the hard-margin classifier for linearly  classifiable input data. This is called the primal problem [].   \item \textbf{Nearest Neighbors.} The principle behind nearest neighbor methods is to find a predefined number of training samples closest in distance to the new point, and predict the label from these.  \end{document}

Which book (free or otherwise) was the most useful to you when you started learning LaTeX?  I am frequently asked this question by friends who want to learn LaTeX, and I recommend the book which got me started, , but I feel that there might be better options around.  Also see .


Prove: A group of order 315 with a normal 3-Sylow group is Abelian. I know that $315 = 3^2\times5\times7$ I've tried using Sylow's theorems on 5, 7 but haven't got anywhere meaningful. I would appreciate any help.

in Dummit and Foote , an exercise asked me to prove that , if $G$ is a group of order $315$ , $G$ has a normal sylow $3$-subgroup then , $G$ is abelian .  this is exercise number $27$ , section $5$ , chapter $4$  my method on proving this is showing that $ |G| = |Z(G)|$ as follows   i showed that $|Z(G)|$ $\in$ ${ 9 , 63 , 45 , 315 } $  and  showed that$ |Z(G)|$ is not $63 , 45$ or $9$   so it must be $315 $  but i showed this under two condition ,   first condition: if $X$ is the set of all elements of $G$ of order $5$ , $H$ is the subgroup generated by $X$  then $|H|$is not $315$  second condition : also , if $Y$ is the set of all elements of $G$ of order $7$ , $N$ is the subgroup generated by $Y$ then $|N|$ is not $315$   so , if those two condition are then my method of proving works .   but i don't know how to prove those conditions .   any help ?


My usb drive had some data. I used it as bootable drive for installing Linux on my pc. Now the data is lost can recover the data ?

What steps can I take to try to recover lost or inaccessible data from any storage device?  Answers:   This applies to any computer storage device, e.g. internal/external hard drives, USB sticks, flash memory. The most important thing is to STOP using it, any type of I/O can ruin your chances of a recovery.     We have separate questions covering common problems with USB flash drives in greater detail:


Hello my name is Tyler T. I'm wondering, when will "Ubuntu Kylin 17.10" be officially available to download? Please reply whenever you can, please and thank you.

I want to know where I can find updated information about all the stable and in-development versions of Ubuntu, where I can find this information?     This question is meant to be a canonical question. It expects to answer the following questions:         Is X version stable yet?   Is X version in beta?   Is X version still supported?   What versions are still supported?   What are the versions in Beta/Alpha?   Until where X version will be supported?   Have X version ceased support?   When will be X version released?   Where I can download any release?   When will the next LTS version of Ubuntu be released?         The list is not exhaustive.


I want to edit a few things to my model in QGIS 3.2.2, but first I need to convert this model to Python script.   Is there a way to do it?

In QGIS 3.0, "Processing Modeler" window has no "Export as Python script" button unlike QGIS 2.x.    If you look at the codes (in DlgModeler.ui and ModelerDialog.py files), you see the code lines related to that button.  in ModelerDialog.py (commented):  #self.mActionExportPython.triggered.connect(self.exportAsPython) . . #self.mActionExportPython.setIcon( #            QgsApplication.getThemeIcon('/mActionSaveAsPython.svg'))   in DlgModeler.ui:  <action name="mActionExportPython">   <property name="text">     <string>Export as Python script...</string>   </property>   <property name="toolTip">    <string>Export as Python script</string>   </property> </action>   After some editings I explained , "Export as Python script" button came into view.    Is there a specific reason or is it a mistake?


I have the sequence $a_n=(n^3)\big(\frac{3}{4}\big)^n$ and I need to find whether it converges or not and the limit.  I took the common ratio which is $\frac{3 (n+1)^3}{4 n^3}$ and since $\big|\frac{3}{4}\big|<1$ it converges. I don't know how to find the limit from here.

In other words, how to prove:  For all real constants $a$ and $b$ such that $a > 1$, $$\lim_{n\to\infty}\frac{n^b}{a^n} = 0$$  I know the definition of limit but I feel that it's not enough to prove this theorem.


While stuying group theory, I was wondering how to proof two elements in a group are not conjugate? For example, say we're in the symmetric group $S_8$, and I have to show that the two elements $(1354672)$ and $(18967543)$ are not conjugate. I can see that the orders of both elements are not equal. And order should be conserved under the conjugation map $τ:S_8 → S_8$, since this mapping is an isomorphism. So I think I can conclude that these two elements are not conjugate. But how do can you prove two elements are not conjugate when they have the same order? Or does same order imply conjugation? Thanks in advance!

I have heard that two permutations are conjugate if they have the same cyclic structure. Is there an intuitive way to understand why this is?


I have the apex class that makes the call to two endpoints in the same method like below  @future (callout=true) public static void createSegSubSegment(String jsonBody,String endPoint) {     String clientId = 'xxxxxx';     String clientSecret = 'xxxxx';     String resource = 'xxxxxx';     String tenant_id = 'xxxxx';     String bearerToken = '';             try{                                String reqbody = 'grant_type=client_credentials&client_id='+clientId+'&client_secret='+clientSecret+'&tenant_id='+tenant_id+'&resource='+resource;              Http h = new Http();             HttpRequest req = new HttpRequest();             req.setBody(reqbody);             req.setMethod('POST');             req.setEndpoint('https://..........');             HttpResponse res = h.send(req);              if(res.getstatusCode() == 200 && res.getbody() != null){             deserializeResponse resp1 = (deserializeResponse)JSON.deserialize(res.getbody(),deserializeResponse.class);             bearerToken = resp1.access_token;             }              Http http1 = new Http();             HttpRequest req1 = new HttpRequest();             req1.setMethod('POST');             req1.setTimeout(20000);             req1.setHeader('Authorization','Bearer '+bearerToken);             req1.setEndpoint('https://..........');             req1.setBody(jsonBody);             req1.setHeader('Content-Type', 'application/json;charset=UTF-8');             HttpResponse res1 = http1.send(req1);          }     }    I was able to make the mock call to the 1st endpoint from my test class like below   @IsTest public class calloutTest {     private static testMethod void callFutureMethod() {               .......         .......          Test.startTest();         Test.setMock(HttpCalloutMock.class, new HttpMockCalloutTest());         handleD365Request.createSegSubSegment(jsonBody,endPoint);         Test.stopTest();      }   Where HttpMockCalloutTest is like below  @isTest global class HttpMockCalloutTest implements HttpCalloutMock{     global HttpResponse respond(HTTPRequest req){         HttpResponse res = new HttpResponse();         res.setStatus('OK');         res.setStatusCode(200);         res.setBody('Test Mock Callout');         return res;     } }   How can I make the mock call to the other endpoint.I am little confused as I have the endpoints are called from the same method in the original apex class

I'm trying to unit test the behavior of some code which performs callouts and its logic is dependent on the HTTP status code of the response - 200 vs 401.  The pattern being exercised is familiar:   Make callout Response is (unauthorized) HTTP 401 Logic checks Status value on the response if (status == 200) { /* yay! */ } if (status == 401) { /* make request for auth /* }   retry original callout with newly acquired authorization yay!    I am attempting to test the code's "try, auth, retry" behavior using the MultiStaticResourceCalloutMock but it appears that only a single status code can be set for all requests that the mock provider can respond to using the .setStatusCode(int) method. Is this accurate?  Is there a mechanism for using a single MultiStaticResourceCalloutMock and having it respond with different status codes per URL in the test context?  Is the only solution here to use a Dispatcher such as what Andrew Fawcett documents here in this answer?   Is there another method/mechanism that allows for different status codes to be returned by the mock provider on the HTTPResponse?    Some  showing the one-time usage pattern of the .setStatusCode(200) method and the multimock class.  @isTest private class CalloutMultiStaticClassTest {     @isTest static void testCalloutWithMultipleStaticResources() {         // Use MultiStaticResourceCalloutMock to         // specify fake response for a certain endpoint and          // include response body in a static resource.             MultiStaticResourceCalloutMock multimock = new MultiStaticResourceCalloutMock();         multimock.setStaticResource(             'http://api.salesforce.com/foo/bar', 'mockResponse');         multimock.setStaticResource(             'http://api.salesforce.com/foo/sfdc', 'mockResponse2');         multimock.setStatusCode(200);         multimock.setHeader('Content-Type', 'application/json');          // Set the mock callout mode         Test.setMock(HttpCalloutMock.class, multimock);          // Call the method for the first endpoint         HTTPResponse res = CalloutMultiStaticClass.getInfoFromExternalService(             'http://api.salesforce.com/foo/bar');         // Verify response received          System.assertEquals('{"hah":"fooled you"}', res.getBody());          // Call the method for the second endpoint         HTTPResponse res2 = CalloutMultiStaticClass.getInfoFromExternalService(             'http://api.salesforce.com/foo/sfdc');         // Verify response received          System.assertEquals('{"hah":"fooled you twice"}', res2.getBody());     } }


I am wondering if it is recommended to adhere to a convention of defining labels before or after captions. Moreover, if that is the case, why?

\documentclass{article} \usepackage{algorithm}  \begin{document} \setcounter{section}{54} \section{A section with no label} \begin{algorithm} \label{myalg} \caption{An algorithm with the label `myalg'.} \end{algorithm} Reference to myalg: \ref{myalg}. \end{document}   With this code, the reference givens 55 (the section number); if I move the label after the caption command, I get the correct reference (1).  Why should this be the case? I find it confusing: when thinking about an algorithm as an environment, you expect to be able to label it right after you began it. At the very least I would expect some kind of error or "??" to appear, rather than the previous environment or reference-able entity being used.


I need to prove: $$\frac{a-b}{a} < \ln(\frac{a}{b}) < \frac{a-b}{b}$$ $$0<b<a$$  I tried the substitution $x = a/b$ and analyzing it as three functions, but it led me nowhere.  Any hints would be welcome.

I'm trying to solve this mean value theorem problem but confused where to start,     If $0<a<b$ prove that $(1-\frac{a}{b})<\ln\frac{b}{a}<\frac{b}{a}-1$   Can someone please lend me a hand?


Is there a way to reboot windows 7 with the option of saving the current working session and restoring it after reboot?   So after reboot, my browser is automatically launched without losing any tabs, Word automatically brings me up to the current doc I am working on, etc.

I find that at the end of a long day, I sometimes have a large number of programs running. All which I will need to use tomorrow. Normally, this isn't an issue, I can simply lock the machine and come back tomorrow. My problem arrises when windows update launches in the middle of the night and force restarts my computer. That in turns closes all my open software. I of course save everything regularly so I don't loose anything, but I waste time reopening all of those resources whenever there is a restart.   [EDIT]  I should clarify that I still want to be able to restart my computer when an update comes down. Preventing the restart only delays the problem until later. I should have been more specific in that I want to be able to recover my working environment after a restart for any reason. Things like scheduled maintence, power loss, updates, and software installs.  [EDIT]  I can't simply have them setup to launch at startup becasuse those files change from week to week. So I need something that monitors what I have open, and gives me the option to "recover" those software sessions when I log back in.  Anyone have any suggestions on what I can do? I'd even be willing to purchase software to do this for me if that is the only option.  Thanks


Any field (in the physics sense of the word) is a function.  But is any function a field? It seems that one might construct a function that returns a tuple consisting of $6$, temperature and electric potential. We would not consider that a field, right? So where is the line?  Basically I am looking for a decent definition of the term field.

I really confused if there is a function (mostly in physics, functions represents physical quantities) which is not a field? I feel all functions in physics are fields. Is there any functions which are not fields? I see a lot of questions in stackexchange about functions and fields. But no one nail down the difference between functions and a fields in Physics, other than answers resembling textbook explanations.


I have a peculiar problem of requiring usb port only for powering my wifi enabled USB powered Dongle. Hope you understand. I have some application that will work only in Wifi. But now when I connect it through wire to my laptop it uses the driver and connect to it as a wired connection. I do not want it to connect it wired but it should use only the wifi of the device. This is possible if only my port is considered to be only a power source and not an interface to the pC OS. Thanks in advance.

On Windows, is there any way to make some USB ports to be charge-only? I do not want to alter the settings of the devices; I want to change the settings of the USB ports on Windows, so that any device I connect to those ports will be only charged.  Is this possible?


Prove that $(x^n + y^n)$ is divisible by $(x + y)$ if $n$ is odd.   I don’t know how to proceed. Help please.

I read somewhere that     $(a^n - b^n)$         It is always divisible by $a-b$.   When $n$ is even it is also divisible by $a+b$.   When $n$ is odd it is not divisible by $a+b$.      and     $(a^n + b^n)$         It is never divisible by $a-b$.   When $n$ is odd it is divisible by $a+b$.   When $n$ is even it is not divisible by $a+b$.      I wonder what's the proof for this.  First postulate is clear. $(a-b)$ would or would not be a factor. Any light on others?


I'm currently studying Cayley-Hamilton proof, but I think I'm missing something massive. The theorem states that an endomorphism $\phi$ cancels its characteristic polynomial. I don't understand why the proof is not trivial. Let $A$ be a matrix of $\phi$ in a basis $\mathcal{B}$. We know that the characteristic polynomial of $A$ is the same as $\phi$ no matter which basis of the vector space we take. Then, $$P_A(A)=\det(A-AI)=\det(A-A)=0$$ So the proof should be trivial, I don't understand where my error is.

Cayley Hamilton Theorem states that if $A$ is an $n \times n$ matrix over the field $F$ then $p(A) = 0$.  We note that $p(\lambda) = \det(\lambda I - A)$. Hence, why can't we just substitute $\lambda$ with $A$ and directly prove Cayley-Hamilton Theorem by saying that $p(A) = p(\lambda) = \det(\lambda I - A) = \det(AI - A) = 0$?


In Harry Potter, Dudley has a Playstation, but wizards are still using quills instead of pens(and candles instead of electricity in Hogwarts). Is there any reason wizards don't use more recent technology?

I noticed, while reading up on the Hogwarts Express, that the engine ran on steam originally, but by 1990 was running fully on magic.  While steam is an older technology, it's still technology and it's interesting even something as simple as steam power was phased out by magickers.  The International Statute of Secrecy was signed in the 1690s, which is after the early steam-driven piston engines, but before steam engines were used for trains and the type of engine used for the Hogwarts Express would not have existed until the mid to late 1800s (at least -- I'm not an expert) and it would not have been out of place in the 1930s, when the Hogwarts Express was made.  This indicates that, on some level, the magickers must have been keeping up with some level of technology.  Other than this, we see almost no signs of the use of science or technology.  Did the magical community always shun any technology, or did they use it up until the International Statute of Secrecy, or was there some other point where magic started diverging from technology?


All I'm trying to do is print the elements in a boolean array. But instead of getting the values of the elements which are either true or false, I get a weird output like this [Z@4517d9a3. I have read about the toString but this applies to string arrays. Here is my code : public class Class{       public static void main(String[] args) {                  boolean a[] =  {true, false, true, false};         boolean[] x = show(a);         System.out.println(x);      }          public static boolean[] show(boolean a[]) {                  return a;     } }

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


When using the spell Tongues, is it obvious that you are using a spell to be understood, or would it be possible to convince someone that you know the language?  For example, if you wanted to disguise yourself as an enemy, could you use Tongues to speak the correct language and blend in?

I would like to play a character who excels in impersonating people. Of course, a high Deception skill comes in handy. But what if I want to impersonate an elf, a dragonborn or an orc? (Alter Self, a Disguise Kit or other such tricks are viable options). People would probably expect me to speak Elvish, Draconic or Orcish. And that's my problem. I can grab some languages with the changeling race, and some more with an appropriate background. I think a Knowledge Cleric would also get some extra languages. But still, my character can never know EVERY language.  That’s where the Tongues spell comes into play. In older editions this spell would let you speak any language. But I’m not sure about the 5th edition version of Tongues. It only says …     This spell grants the creature you touch the ability to understand any   spoken language it hears. Moreover, when the target speaks, any   creature that knows at least one language can hear the target and   understands what it says.   Can I fool listeners with this spell? Would an elf actually believe that I talk to them in Elvish? Or would any listener recognize that I only make myself comprehensible with magic?


I am having trouble with this proof.     If $a,b$ are integers, then $(a+b)^3 \equiv a^3 + b^3 \pmod{3}$     What I am confused about is using the definition of modulo. So can $b^3 \pmod{3}$ be written as $3\, |\, [b^3 - (a+b)^3]?$ How does the $a^3$ term come into play with writing the modulo definition.   Also I apologize for the messiness of the math equations, I am new to math exchange and haven't gotten the TeX concepts down yet.

a, b are integers. p is prime. I want to prove: $(a+b)^{p} \equiv a^p + b^p \pmod p$  I know about Fermat's little theorem, but I still can't get it I know this is valid: $(a+b)^{p} \equiv a+b \pmod p$ but from there I don't know what to do.  Also I thought about $(a+b)^{p} = \sum_{k=0}^{p}\binom{p}{k}a^{k}b^{p-k}=\binom{p}{0}b^{p}+\sum_{k=1}^{p-1} \binom{p}{k} a^{k}b^{p-k}+\binom{p}{p}a^{p}=b^{p}+\sum_{k=1}^{p-1}\binom{p}{k}a^{k}b^{p-k}+a^{p}$ Any ideas?  Thanks!


Does anyone know how to evaluate the following limit?  $\lim_{x\to0}(\frac{\sin{x}}{{x}})^{\frac{1}{x}}$  The answer is 1 , but I want to see a step by step solution if possible.

$$\lim _{x \rightarrow 0} \left(\frac{ \sin x}{x}\right)^{1/x}$$  I have spent an hour on the above limit and have no work to show. I tried using L'Hopital's Rule, but just kept going around in circles. Any help would be appreciated. Thank you.


Trying to print possible number combinations in single line as list but the list have wrong output. My output is like this:  [[1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1]]   When it should be like this:  [0, 0, 0] [0, 0, 1] [0, 1, 0] [0, 1, 1] [1, 0, 0] [1, 0, 1] [1, 1, 0] [1, 1, 1]   My code is  if __name__ == '__main__':     x = 1     y = 1     z = 1  kordinat = ["x","y","z"] result = [] for xx in range(x+1):     kordinat[0] = xx     for yy in range(y+1):         kordinat[1] = yy         for zz in range(z+1):             kordinat[2]= zz             print(kordinat)             result.append(kordinat) print(result)

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


i want to create 2 div and text box in java script like that

  <input type="text">

   is it possible?

I have an HTML string representing an element: '
text
'. I'd like to append it to an element in the DOM (a ul in my case). How can I do this with Prototype or with DOM methods?  (I know i could do this easily in jQuery, but unfortunately we're not using jQuery.)


Loose hub bearings may be cheaper to mass produce, but why wouldn't sealed hub bearings be one of the first upgrades to a bike?  It seems that most of us choose loose bearings.  I'm thinking of putting in a set of sealed bearings front and back and be done with it.

My LBS recommended cartridge hubs to me. Here are my doubts.  Seeing as how I never ride in the rain or any such wet substances, I don't really need the "completely sealed" feature.  Sheldon Brown says that if taken care of, the body of a loose-ball hub will last indefinitely. (not the balls and cones). So if you maintain your hub, you should be able to indefinitely avoid having to re-spoke your wheel.  Sealed bottom brackets make sense, because it's easy to pull your cranks off and swap it out. But if you have a cartridge hub, when it wears out you will need to re-spoke your wheel. Am I right about that, or do cartridge hubs have a system for just replacing the bearings?  Also, is it possible that a cartridge hub would last as long as the rim? Then you would just replace the whole wheel once it started having problems.


I'm trying to use another class to return data from another class. This class will either return a password, or a key, depending on the arguments sent to the class.  This is the function in the class that returns the data:  public static String main(String args[]){         if (!args.equals(null)){             String gen = generatePassword(args[1]);             return gen;         }else{             String gen = generateRandomString();             return gen;         }     }   My error is:  Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at me.GaryIsASloth.KeyGenerator.main(KeyGenerator.java:34)   With 34 referring to:  if (!args.equals(null)){   The arguments provided will either be "pass", following "true"/"false" which will tell the class whether to include special characters or not.  Or for the key the args will be null.  I had the class working perfectly when I had it working with the key, and then after modification it worked fine with the password too. However I can't get it to work with both, dependant on the arguments. I've tried null check and length check. What can I do?

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?


A CSE student has knowledge about some programming language. So, learning LaTeX is not so hard for him. And he also familiar about some indentation and syntax of different language.   Now , what is the starting point and practice for a CSE student for leaning LaTeX completely.   In addition  , if he uses a Linux as OS and  vim as text editor.

Which book (free or otherwise) was the most useful to you when you started learning LaTeX?  I am frequently asked this question by friends who want to learn LaTeX, and I recommend the book which got me started, , but I feel that there might be better options around.  Also see .


Let $x$ be a positive real number. Then  $A.\ x^2+\pi ^2+x^{2\pi}>x\pi+(\pi+x)x^\pi$  $B.\ x^\pi+\pi^x>x^{2\pi}+\pi^{2x}$  $C.\ x^2+\pi ^2+x^{2\pi}<x\pi+(\pi+x)x^\pi$  $D.\ $none of the above  Which one is correct? And how to prove that? Any hints would be appreciated.

Let $x$ be a positive real number. Then  (A) $ x^{2} + \pi^{2} + x^{2\pi}> x\pi+ (\pi+x)x^{\pi} $  (B) $ x^{\pi} + \pi^{x}> x^{2\pi}+ \pi^{2x} $  (C) $ \pi x +(\pi+x)x^{\pi}>x^2 + \pi^2 + x^{2\pi} $  (D) none of the above.  I've tried using AM GM inequality. But not been able to solve. It became more cumbersome. And I know it can be solved using substitution (x=1). But I want to know the process, intuition to such problems Help??


so all my files on my backup server are named archive-2021-03-18.zip, archive-2021-03-19.zip, etc. I want to set up a cronjob to delete files where the name is older than 7 days. Would someone be able to assist me please?

If I have a folder of files with their filenames as the date they were created:  2019_04_30.txt 2019_04_15.txt 2019_04_10.txt 2019_02_20.txt 2019_01_05.txt   How would I compare the files names against todays current date  $ date "+%Y_%m_%d" >>> 2019_04_30   If the file names date is greater than 30 days then delete it. I would expect to end up with  2019_04_30.txt 2019_04_15.txt 2019_04_10.txt   I don't have to follow this naming convention, I could use a more suitable date format.


For example   \documentclass[14pt,twoside]{extreport} \renewcommand{\baselinestretch}{1.5}  \usepackage[utf8]{inputenc} \usepackage{graphicx} \usepackage[a4paper,width=150mm,top=25mm,bottom=25mm,bindingoffset=6mm]{geometry} \usepackage{fancyhdr} \pagestyle{fancy} \fancyhead{} \fancyhead{} \fancyhead[RO,LE]{\small\leftmark } \usepackage{amsfonts} \usepackage{graphicx} \usepackage{amsthm} \usepackage{amsmath} \usepackage[english]{babel}  \begin{document} First, we compute the following products: \begin{align*} R_2R_5&=a_2 a_5 t^2+\left(a_5 b_2+a_2 b_5\right) t+b_2 b_5,\\ R_2 R_3 R_5&=a_2 a_3 a_5 t^3+\left(a_3 a_5 b_2+a_2 a_5 b_3+a_2 a_3 b_5\right) t^2+\left(a_5 b_2 b_3+a_2 b_5 b_3+a_3 b_2 b_5\right) t\\ &+b_2 b_3 b_5,\\ R_4 R_6&=a_4 a_6 t^2+\left(a_6 b_4+a_4 b_6\right) t+b_4 b_6,\\ R_3 R_4 R_6&=a_3 a_4 a_6 t^3+\left(a_4 a_6 b_3+a_3 a_6 b_4+a_3 a_4 b_6\right) t^2+\left(a_6 b_3 b_4+a_3 b_6 b_4+a_4 b_3 b_6\right) t\\ &+b_3 b_4 b_6, \end{align*} By replacement, ordering by powers of t and identifying, we obtain a system whose solutions describe the number of straight lines situated on the "reliability" hypersurface. We write the system ordering by the coefficients of the powers of degree from zero to five,relative to t: \begin{align*} b_7&=b_2 b_5+ b_2 b_3 b_5 - b_2 b_3 b_6 b_5 + b_3 b_6 b_5 - b_2 b_4 b_6 b_5 + b_2 b_3 b_4 b_6 b_5 - b_3 b_4 b_6 b_5 + b_3 b_4 b_6 + b_4 b_6, \end{align*} Starting from the last equation, at least one of the numbers $a_i$; $i = 2,\ldots , 6$ must be zero (number of cases: $C_1^5 + C_2^5 + C_3^5 + C_4^5 = 30)$. So the straight-lines are parallel to some hyperplane of coordinates. The first equation shows that at t = 0, point $(b_2,\ldots, b_7)$ is on the "reliability" hypersurface. This remark requires the following procedure: we choose arbitrarily $b_2, \ldots ,b_6$, and compute $b_7$. We replace the values $(b_2,\ldots, b_7)$ in the remaining equations. If the new system, in unknown $(a_2,\ldots, a_7)$ , it has a solution with at least a nonzero component, then there exists one straight line passing through the point $(b_2,\ldots, b_7)$  and lying on the "reliability" hypersurface. Explicitly, after solving the algebraic system, we have the following cases:     \end{document}   The result is this   How can I adjust the equation within the limits of the text?  thanks for the help

I am having the following equation:  \begin{equation}   Q(\lambda,\hat{\lambda}) = -\frac{1}{2} P(O \mid \lambda ) \sum_s \sum_m \sum_t \gamma_m^{(s)} (t) \left( n \log(2 \pi ) + \log \left| C_m^{(s)} \right| + \left( \mathbf{o}_t - \hat{\mu}_m^{(s)} \right) ^T C_m^{(s)-1} \left(\mathbf{o}_t - \hat{\mu}_m^{(s)}\right) \right) \end{equation}   which does not very well fit on one line. How can I split this over two lines? What I have in mind is that I specify the splitting place, and that the first line is left aligned and the second line right aligned to make clear that it is still the same equation.  The linebreak \\ does not work.


I'm comparing two classification models by computing the area under ROC and Precision-Recall curves.   However sometimes one model is better with AU-ROC but worse in AU-PR, and other times it's better in AU-PR but worse in AU-ROC. (Outdated sentence, please see edit)  Based on that I made a conclusion based on my understanding on the AU-ROC and AU-PR, and I just want to make sure that my understanding/conclusions are corrects.  If one method is better in AU-ROC but worse in AU-PR, then the method is better in Recall but worse in Precision. So you should use this method when you want high recall.  If one method is better in AU-PR but worse in AU-ROC, then the method is better in Precision but worse in Recall. So you should use this method when you want high precision.  Are my understanding/conclusions correct? Precision-Recall tradeoff.  Edit:  The case is the following: one model is always better in AU-ROC. While the other is always better in AU-PR.  So if my conclusions are incorrect, then what conclusion/s can one make from such a result? I'm interested in the conclusions of this because it allows me to make a rule to select each method. So if one method is always better in AU-ROC, then I would like to say that one should select the method if his priority is a high recall for example.

I have two methods/classifiers (completely different models) that I need to decide which one is better. The dataset is imbalanced. I trained both classifiers on the same dataset and then I computed the ROC-AUC and the Precision-Recall-AUC (PR-AUC). Then the surprise came!   Method 1 is better than method 2 when I compare them using ROC-AUC. Method 2 is better than method 1 when I compare them using PR-AUC.   Now I'm so confused! How to say which method is better? As far as I know from  that if the ROC-AUC is high, then PR-AUC is also high. So if the ROC curve of method-1 dominates, so should method-1's PR curve. Is my understanding incorrect? Or am I missing something? Because I'm really going crazy!


I've seen it printed multiple places,  for example, that the reason orbits are elliptical is because the gravitational law has an inverse square of the radius. Why does this make the orbits elliptical?

How can analytically be  the ?   I found some extremely synthetic equations which from the  (in particular $\mathbf{F} = m \mathbf{a}$) tried to obtain the Kepler's laws, but even if it seemed to be a nice procedure they were too much incomplete.


I am building a clock and it works mostly;   The issue with my code is that I cant figure out how to have one constantly changing text instead of a billion texts with only the newly created text with the correct time   could someone please tell me how to change erase and or update this so it will fix my problem pls  import java.util.Date; import java.text.SimpleDateFormat;  public class abugnoisyclockmainclass {     public static void telltime () {        for(;;) {            Date computertime= new Date();            SimpleDateFormat time = new SimpleDateFormat("E M-d-y        h:m:s a ");            System.out.println(time.format(computertime));        }     }      public static void main(String[] args) {         abugnoisyclockmainclass.telltime();     } }

How can I return to the start of a line and overwrite what has already been output on the console? The following does not appear to work:  System.out.print(mystuff+'\r');


Reading about tele extenders for lens and how they change the focal length/field of view I came up with the idea if there is something/some way to shorten the focal length of the lens. And the question is: Is there something like this?   Unfortunately search engines do not provide me information about this :)  Edit: I do not care about the light. My target is to find way to replace for example quite expensive lens like Canon 11-24/F4 with Canon 16-35/F4. Some degree of degradation of IQ is expected and accepted

I have been reading couple of times now about those new  for mirrorless cameras. They are being reviewed as improving the low-light performance of a lens by one full stop.   In my knowledge, when you add elements to a lens, you would make the image not better, but rather worse. Can someone explain me how this works in general terms?


Define $f(x)$ for $x\in[0,1]$ by $f(\frac pq)=\frac1q$ if $p$ and $q$ are relatively prime, and $f(x)=0$ if $x$ is irrational.  How can we see that $f$ is discontinuous at all rational points and continuous at all irrational points?  Furthermore, if $g(\frac pq)=q$ for $(p,q)=1$ and zero otherwise, how can we see that $g$ is not bounded on any subinterval of $[0,1]$?

Consider the function:  $f(x)= \begin{cases}  1/n \quad &\text{if $x= m/n$ in simplest form} \\ 0 \quad &\text{if $x \in \mathbb{R}\setminus\mathbb{Q}$}  \end{cases} $  Prove that the function is continuous at every irrational point and also that the function is not continuous at every rational point.  Also, we can say that the function is continuous at some point $k$ if $\displaystyle\lim_{x \to k} f(x)=f(k)$.  I was thinking of doing an epsilon delta proof backwards using the fact that $\mathbb{Q}$ is dense in $\mathbb{R}$ for rational points and irrational points.  Any ways on how to expand on this are welcome.


Critical hits double all the dice rolls. Since Superiority Dice are dice rolls too, do they get doubled on a crit? That is, if a Fighter attacks, rolls a 20, and decides to use a combat maneuver, do they roll 2d8 for bonus damage?  Case in point: a Rogue3(Assassin)/Fighter3(Battle Master) multiclassed character deals a surprise round. Since they auto-crit due to Assassinate if they hit, they can also tack on a maneuver to add a guaranteed 2d8 damage (assuming the maneuver adds that damage in), on top of the 6d6 damage from sneak attack.  Related: , but I don't think it's a duplicate as this is concerning a more specific scenario with a multiclassed character.

The Battle Master fighter has access to a number of maneuvers that add a superiority die to the damage roll. For instance, the Trip Attack maneuver says (PHB, p. 74):     When you hit a creature with a weapon attack, you can expend one   superiority die to attempt to knock the target down. You add the   superiority die to the attack’s damage roll, and if the target is   Large or smaller, it must make a Strength saving throw. On a failed   save, you knock the target prone.   The Critical Hits rule states (PHB, p. 196):     When you score a critical hit, you get to roll extra dice for the   attack’s damage against the target. Roll all of the attack’s damage   dice twice and add them together. Then add any relevant modifiers as   normal. [...] If the attack involves other damage dice, such as from   the rogue’s Sneak Attack feature, you roll those dice twice as well.   During our game, the fighter PC rolled a critical hit. He then wanted to use a superiority die to use the Trip Attack maneuver to trip the enemy. Based on the above rules, is the damage from the superiority die also doubled?  I'm assuming the answer is yes based on the last statement in the Critical Hits section, but I wanted to confirm.


I'd like to know what software provides better performance in business forecasting for thousands of SKU. Here the data is taken through databases.   I know three alternatives:   Autobox SAS Forecast PRO   I'm looking for an option that can forecast every SKU automatically, given an error measure (preferably MAE).  I can't find a comparison for these sofware with the same data. What do you know about the performance of them?

I have question on evaluating forecasting software with expert systems:  Are there any objective assessment (not from the manufacturer) on expert forecasting software in the literature?   I found two references, but both are old:   Principles of Forecasting (2001) Armstrong Forecasting methods and applications (1998) Makridakis et al.    and  seem to be two expert systems in the market, are there any comparisons made on these two software?  Are there any other software that have expert systems?


I was reading about reflection and refraction on BBC Bitesize and I can't understand why frequency is a constant in the wave speed equation. I can't visualise the idea of it. I know that wave speed and wavelength are proportional to each other but how can I tell the speed of a wave by looking at a random oscillation?  Here's where I got confused:  (the bottom of the page about the water)

When light passes from one medium to another its velocity and wavelength change. Why doesn't frequency change in this phenomenon?


i  had graphic card of  nividia gforce210 but while I want to enable gpu in cycle render then it show the "none" in cycle computer device please help me.

It looks like this is a common problem, but I can't find any forum post that has a solution to my situation: I have no CUDA tab in system settings in Blender.   My data: Windows 10 64bit  Blender v2.77  Geforce GT 330M - driver Nvidia 341.95 (newest avalible driver.)  Is there someone who can help me to find out what can be the issue?


which or what? I have always been taught that which is used when you can choose from a limited, given number of choices. What when you have an unlimited choice.  Which country has a higher GNP, Germany or France? What country would you like to go to on holiday?  On the internet I see people use what and which in both cases. Is this correct? Is the rule I was taught old-fashioned?

What are the grammatical rules determining whether to use which or what?  I usually go by intuition. It's "What car are you looking at?" and "What bicycle do you like most?" but "Which song did you sing?" Quite often, I don't know whether to use what or which.  How can I tell?


It almost looks as if :    The downvotes are on:          If there's anything common among these downvoted questions it could be questions that I have not accepted and/or that were maybe were not good ideas to start with - but hey, that's part of why we ask questions ;-)  Has anyone else noticed this behaviour (at least one person has, see the undownvotes). It does not look as if someone has taken offence at something I did, there would be more downvotes then. I'm curious what can be going on, but I'm afraid there's not much I can find out at my level.

I just noticed that I lost a bunch of points from my reputation score, and I used the "reputation" tab on my user profile page to try and track down the cause.  During my investigation, I noticed there was an unusual event of type "reversal". In the normal place of a question title, it says "voting corrected".     What does this mean, and what caused it?  Did I do something wrong? Why did I lose all of that reputation? Is the system punishing me for leaving too many good answers?  Is there any way to earn it back?


public class Example {  public static void main(String[] args) {      String a = "abc"; // Line 5     String b = a + "d"; // Line 6     String c = "abc"+ "d"; // Line 7     String d = "abcd"; //Line 8      System.out.println(b==c); //Line 10      System.out.println(c==d); //Line 11 } }   Output:falsetrue  If we see Ref. variable 'b' is pointing "abcd" string object and Ref. variable 'c' is also pointing same String object i.e "abcd" but when we check equality using == (double equal operator) operator it prints false at Line 10. But if we make Ref. variable 'a' as final then it prints true at Line 10  So i am bit confuse. Can any one tell me what is happening behind it?

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


Scenario:  Player A has two unblocked creatures attacking player B, each with power 3 with an ability that triggers upon dealing combat damage to a player, let's say  and . Player B has a damage prevention effect preventing the next 4 damage dealt to himself. No creatures have first strike and no other replacement or prevention effects are active.  Which of the two creatures abilities triggers and why?

I got attacked by 2  (1/1 infect unblockable), a  (3/1 unblockable) paired with  (2/1 and when paired both creatures get "Whenever this creature deals damage to an opponent, draw a card") and Tandem Lookout itself (which was unblockable due to an effect).  I tapped my  (tap: "Prevent the next 2 damage that would be dealt to target creature or player this turn") to prevent 2 damage to me.  My question is: who's damage will be prevented?  Does my opponent decide the order in which the attacking creatures attack during the Declare Attackers Step? Or does he decide that during the Combat Damage Step?  We couldn't find this in the Comp. Rules, so my opponent said his Latch Seeker(3/1) was prevented by 2, but this way I got 2 poison counters and he drew 2 cards. I would have liked to prevent the two poison counters or to only let him draw 1 card (by preventing Tandem lookout).


Do concepts in Newtonian Mechanics such as Normal force, etc. still hold true?  I don’t mean if you use newtonian mechanics, will it still chunk out the correct computation.  What i mean is that does the equations of Newton accurately describe the universe? Im also pointing to Newton’s concept of gravity where objects pull, whereas Einstein’s predictions says that gravity pushes via waves in space-time.

What is the relationship of  and  ? Namely, which laws does GR replace of Newtonian Mechanics, and which laws of Newtonian Mechanics are incorporated into it. Or is GR a complete replacement and overhaul?


I went through the first page of an  that asks a similar question and doesn't get an answer. Now that there is more information on the subject, I'd like to know for a build I'm working on, a Half-Elf Sorcerer/Oracle/Mystic Theurge: to what extent are half-breeds treated as humans?  Normally I'd just assume that half-elves/orcs can lean towards whatever side of their ancestry they want, but it seems to be controversial enough that I do need to ask what the RAW is. What are half-humans allowed to take that is usually reserved for their halves only?  I'm looking primarily for a RAW answer, but I'd take an RAI answer if no RAW answer exists. Normally I'd be the first to agree that "effects" has nothing to do with favored class bonuses, but it would appear to be accepted that half-elves can take human-only classes, which are not effects by any means.  The half-races in question are primarily  and , and at least as far as Favored Class Bonus is concerned the side-bar on those two pages would appear to confirm that yes, half-elves/orcs can take the Favored Class Bonuses of either elves/orcs or humans, but in a broader sense it could also apply to the planar races (aasimars, tieflings, sylphs, ifrits, oreads, and undines, possibly more) that have the following ability (or close variation thereof; this is taken from ):     Scion of Humanity Some aasimars’ heavenly ancestry is extremely distant. An aasimar with this racial trait counts as an outsider (native) and a humanoid (human) for any effect related to race, including feat prerequisites and spells that affect humanoids. She can pass for human without using the Disguise skill. This racial trait replaces the Celestial language and alters the native subtype.   The biggest reason that this partially extends to them as well is because they now have the Humanoid (Human) type with this trait, which is fine by itself, but according to the sidebar on the same page any humanoid could be an aasimar (or any of the other planar races). As a sub-question to this one, if the prerequisite for human/elf/orc/etc.-only feats, race traits, classes, favored class bonuses, etc. is to have the "Human/Elf/Orc/etc." subtype... would these races with that ability be able to qualify for those things as well?

In Pathfinder, half-elves have the following racial trait:     Elf Blood: Half-elves count as both elves and humans for any effect related to race.   Since now I always considered that it meant that a half-elf could for example be an  which is "available to elven oracles", or a  which has "race: elf" as a prerequisite.  But it seems to me more and more odd that this is possible, on top of the other stuff that is specifically designed for half-elves.  What is the official ruling on the subject? Can a half-elf took an archetype, a prestige class, a feat or other stuff with "being an elf" as a prerequisite?  As a sidenote I deliberately didn't put "elf" as a tag since the same question could be asked for any race with the "X blood" racial trait (eg half-orcs).


I got the following message when I was installing mcrypt on Ubuntu 18.10:  dpkg: error processing package libswscale5:amd64 (--configure):  package is in a very bad inconsistent state; you should  reinstall it before attempting configuration   How do I re-install libswscale5?

Recently, i was installing the new version from 13.04 to 13.10 ubuntu while also watching a video.  Well, guess what happened, my desktop crashed for like 4 minutes and then upon gaining access to the desktop again everything seemed messed up like box symbols where characters should be.  I know it was a bad idea but i decided to reboot halting the installation process and now i am stuck with this error.  dpkg: error processing unity-lens-photos (--configure): package is in a very bad inconsistent state - you should reinstall it before attempting configuration.  Errors were encountered while processing: untity-lens-photos e: subprocess /usr/bin/dpkg returned an error code (1).   And it pretty much pops up everytime i try to upgrade, or install anything.  This was after i finished updating the rest of my files.  I have tried many things and read many threads.  I am really lost right now, please help.  Also i have no access to a panel and i am currently trying everything in the terminal.  Attempts to install a gnome panel have been halted by the error.


I want to insert into a table which i created just before inserting. The Tablename is in a variable (e.g. $table).  The error message states that the problem is near that variable.  I tried $table '$table' '$table' '.$table.' '{$table}' '.{$table}.'   CODE:  $sql = "INSERT INTO $table (Absender,TimestampGesendet,Typ,Nachricht,Status,Status_Termin)                  VALUES ('{$userid}','{$timestamp_gesendet}','{$typ}','{$nachricht}','0','{$status_termin}')";   ERRORMESSAGE:     INSERT into 90 (text,id_absender,TIMESTAMP_gesendet,TIMESTAMP_empfangen,Status,Typ) VALUES (,91,1559806806,1559806806,'0',1)   You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '90 (text,id_absender,TIMESTAMP_gesendet,TIMESTAMP_empfangen,Status,Typ) VALUES (' at line 1Error: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '90 <-THIS IS THE TABLENAME! (text,id_absender,TIMESTAMP_gesendet,TIMESTAMP_empfangen,Status,Typ) VALUES (' at line 1   backclikcs doesn't work at all, as mentioned above. can there be issues if the source-code is in utf-8?

I'm thinking of having a program that dynamically creates new tables as the need arises. Can I have tables named with just numbers in MySQL?


How can I copy a Windows7 DVD to another DVD using a single DVD drive?

Is there any built-in way of copying DVDs in Windows 7 or do I need to install a third party tool?


Question: Can a number written using one hundreds 0's, one hundred 1's and one hundred 2's be a perfect square?  I have no idea where to start.

Can a number with $100$ $0$'s $100$ $1$'s and $100$ $2$'s ever be a perfect square? I have no idea where to even start. Some hints would be nice. Thanks in advance :)


I am doing lead conversion process.  Is it possible to convert the lead without creating the account record?

Once a lead is converted it automatically creates an account, contact and one opportunity. But in my case i want to display the result without creating an Account. Please provide me with a sample code.  Any help will be appreciated...