I encountered a bug regarding the Next button in the review section.     Steps to reproduce:         Review a "first post".   Complete the first review regularly and review another "first post".   Start editing the post.   Wait for some time, so that someone else likely completes the review.   Click the browser's back button.   Try clicking the Next-button.         Expected behavior:      The next review is being displayed, or a message appears stating that there are no posts to review.      Current behavior:      Nothing happens. The button looks "clickable", but cannot be clicked.   After reloading the page the button gets clickable.   Edit: After several "edit" -> "cancel" -> "edit" -> "back" cycles I managed to get this result (Note the two "cancel"-links at the top):

These are the steps to reproduce what I noticed.   I clicked on the link to review the suggested edits, and I was given  as post to review I clicked on "Skip" to pass to the next I was taken to  I clicked on "improve" by mistake When I noticed that, I clicked on the back button to go out of the edit page   After I did that, I was shown the previous post to review, but in that page the review buttons didn't work. What I described happens even in the case the suggested edit is already approved/rejected; in that case the "next" button doesn't work.  Is this a bug, or is it expected to happen?  It happens in Firefox 17, and Safari 6.0.1, and Google Chrome 22.0.1229.94. Stack Exchange revision is 2012.10.20.4492.


If $\sum $$a_{n}$ is convergent, prove  $\sum \frac{a_n}{n}$ is also convergent.  I would say that $a_{n}\geq \frac{a_{n}}{n}$ so being $a_{n}$ convergent, $\frac{a_n}{n}$ also has to be convergent.  However, I think it is not enough...

I know if $\sum{a_n}$ converges absolutely then $\sum{\frac{a_n}{n}}$ converges since $0\le \frac{|a_n|}{n} \le |a_n| $ for all $n$ so it converges absolutely by the basic comparison test and therefore converges. However, I cannot prove the convergence of $\sum \frac{a_n}{n}$ if $\sum{a_n}$ converges but not absolutely even though I suspect it to be true. Can you give me a proof or a counterexample for this?


We know that two parallel photons have no gravitational effect on each other because they never pass through each other's light cone.  The question is, what happens to anti-parallel photons?  It stands to reason they pass through each other's light cone at some point after they pass each other giving an opportunity to exchange energy and bend their paths.  What confuses me however is if the photons are exactly the same color do they redshift each other as if they both redshifted this would lead to missing energy.

In general relativity, light is subject to gravitational pull.  Does light generate gravitational pull, and do two beams of light attract each other?


I would like not to show my desktop when starting Ubuntu and only show Chrome browser, so that my computer would use less resources because it wouldn't have to draw the desktop. When my project is finished, the goal is only to show web pages, so I don't really have interest in the desktop, that will only be used by admin for technical changes.   Is there anyway to do that? Is it what you English folks call a "kiosk"?

I have made a clean install of Ubuntu 14.04 LTS Desktop and now want's to convert it into a kiosk with a full screen webbrowser.  This was previously done in 10.04 and worked perfect, but due to hardware changes (graphics) we are forced to use version 14.04.  I have created a kiosk.desktop in /usr/share/xsessions and a shell script called kiosk.sh that launches firefox with r-kiosk installed. The shell script is executable. A user called "kiosk" is set to autologin (in /etc/lightdm/lightdm.conf).  But now i'm stuck. I'm want the kiosk.sh to be run when the kiosk user session is started.   In previous versions this could be done in the GUI tool "Login Screen Settings" or in /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf.  I have changed 50-ubuntu.conf to "user-session=kiosk" but it doesn't start. The "Login Screen Settings" tool can't be found. Has it been replaced by another utility in 14.04?  Placing a kiosk.sh.desktop in ~/kiosk/.config/autostart works, but the gnome-desktop is shown before firefox starts in fullscreen mode making it possible for the users to interact with the desktop.  What is to correct/best way to start firefox in fullscreen after user autologin?  Thanks  Thomas


I have a question about pages indexed, hope you can help me out, thank you in advance.   Recently, we found our French site's two download pages are not indexed by Google. The URL of the French site is: www.imobie.fr, the two non-indexed pages are:    and        Our website is not a new site, and the two pages always rank well in Google for several years, because the organic keywords are brand related, like AnyTrans Download or PhoneRescue Download, or just search AnyTrans or Download. Recently, we found the two pages' organic traffic declined sharply and then found they had disappeared from Google SERP, and they are not indexed by Google.   Then we checked Google Webmaster tool, in the Coverage > Crawled – currently not indexed found the two pages, then submitted them to Google for index yesterday, and found they are still not indexed by Google today. And the Google Analytics shows the organic traffic started to decline sharply from Aug.27th.    About this problem, we had tried the following methods,   Checked the two pages have “no index” tag in the page source – No  Checked robots file and see if we blocked the two pages from crawling - No  Checked the two pages' re=canonical tag and see if they are linked to the wrong pages – No  Checked if the pages for mobile phones has “no index” tag (Because our products are desktop software, for mobile users, we designed some pages to convert mobile users, only work for mobile users. Normally, we add “no index” to block them from Google crawling)  - Yes, they have.  Checked “Remove URLs” to see if we removed the two pages from google SERP by mistake – No.  Submit the two pages to Google via URL Inspection, but they are still not indexed.    So far, the pages are still not indexed by Google. And I just searched site:imobie.fr/anytrans/ download in Bing and yahoo.co.jp, I found I can find  in bing, but can’t in Yahoo. Therefore, I want to know why our pages are disappeared from Search engines’ SERPs, and not indexed, and how to make them indexed again. If possible, also hope you can check if the two pages have any not-friendly codes in the page source.

This is a general, community wiki  question and answer pair intended to address any questions   concerning the reasons a site or specific site contents do not appear   in search engine results.      If your question was closed as a duplicate of this question and you   feel that the information provided here does not provide a sufficient   answer, please open a discussion on .   My site (or specific pages on my site) is not appearing in search engine results.  Why isn't my content indexed and what can I do about it?


I have read this  from  .It says that other Ubuntu flavors of LTS get only 3 years of support. Is this true?   This question is not a duplicate of the linked post as I want to know support time for only other Ubuntu flavors.

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.


Quite often when I'm in a rush, I automatically pull out a USB pendrive or USB cable from an external hard drive from my desktop PC or laptop, without right-clicking on the safely remove icon in the system tray and unplugging via this route. So far nothing untoward has happened every time I have "been in a rush".  What is the rationale behind right clicking on the safely remove icon and can I really lose information on USB media if this is not carried out?  Edit  Is the vunerability of losing such information greatly increased, if the usb media is still flashing at the time of pulling it out of the computer (as opposed to non-flashing)?

When you unplug an USB drive without unmounting, your OS warns you about how dreadful could be such operation for your devices (I'm on OSX).  I usually follow the advice, unmounting before unplugging, but it happened many times (thousands) that, at the end of my tasks, I just unplugged (Hd storage, Cell phones, etc..) and I never ever noticed corrupted data on my devices. Am I lucky or can this annoying warning just be ignored?


I have Windows 10 Pro installed on my 120GB SSD and now there is not enough space even to install win 10 update because some application automatically selects C:\ drive to installation localtion. So I decided to download Ubuntu and put it on a USB drive and "try" it so I don't need to install it. And with Ubuntu I can move all program files to a different drive and I can make a symlink to the files. The problem is that when I try to boot Ubuntu I get a single line saying: [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x52 (or later) I found  question, but if I can't boot up Ubuntu I can't use the sudo apt-get install intel-microcode command.  So how can I boot this up?

I saw several bugs and error messages when I was looking by chance into the tool called "logs".  Being a newbie in Ubuntu I have no idea how to deal with these bugs, where to report them or how to fix them.  Any help to guide me here?  The bug I have (which is listed under important) reads:  [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x52 (or later)


Ubuntu installed some updates, and after the restart, I cannot log in.  It seems to accept, but then beeps and returns to the login screen.  All of the users, including guest do the same thing.  I was looking at some other posts here, and tried some of the suggestions without success.  I looked at the .xsession-errors file but I don't understand the error:  X Error of failed request:  BadValue (integer parameter out of range for operation)   Major opcode of failed request:  155 (GLX)   Minor opcode of failed request:  3 (X_GLXCreateContext)   Value in failed request:  0x0   Serial number of failed request:  34   Current serial number in output stream:  35 openConnection: connect: No such file or directory cannot connect to brltty at :0 upstart: gnome-session (Unity) main process (1751) terminated with status 1 upstart: unity-settings-daemon main process (1737) killed by TERM signal upstart: Disconnected from notified D-Bus bus upstart: logrotate main process (1601) killed by TERM signal upstart: update-notifier-crash (/var/crash/_usr_bin_compiz.1001.crash) main process (1669) killed by TERM signal upstart: update-notifier-crash (/var/crash/_usr_bin_compiz.1002.crash) main process (1671) killed by TERM signal upstart: bamfdaemon main process (1730) killed by TERM signal upstart: hud main process (1735) killed by TERM signal upstart: indicator-bluetooth main process (1795) killed by TERM signal upstart: indicator-power main process (1796) killed by TERM signal upstart: indicator-datetime main process (1797) killed by TERM signal upstart: indicator-application main process (1844) killed by TERM signal upstart: job window-stack-bridge failed to stop   Thanks, David

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I have seen how to convert a picture from color to grayscale .  However, grayscale is not black and white.    Simply put, if a field has color, I want to convert it to black.  All other areas should be white.  So, if a line 6 pixels thick is orange, the other thread's answer will turn the line gray.  The line should be turned solid black.  However, is there a way to convert anything of any color at all (not white) to black?    I am working with Engineering prints, and it simply needs to be black or white. Gray does not work, because certain color lines become “gray” lines.

How can I convert a JPEG photo to black and white (not grayscale) image like output of a FAX scanner, by ImageMagick?


I currently have a signup form that has a username and an optional email field.  I want to make this form appear simpler by getting rid of a field. What has been your users' experience with only using email for username? (Email would then become non-optional). Personally, I don't like this because my email is longer to type than my username. But, I am seeing this more and more. Is it the future?

What is the best solution for an app : Email or username field?  I like email because:   it's unique user will easily remember it's personal (which can be a disadvantage sometimes; Multiple users on the same account)   Unfortunately we usually have to type more letters to login (write the name + @domain.com)


if pygame.sprite.collide_rect(ship,missile) == True:     ship.image = pygame.image.load("lose.jpg")     ship.image = ship.image.convert()     ship.rect = ship.image.get_rect()     break   How do I make it so there is a few second wait while it shows 'lose.jpg' and then breaks and exits the program?

I would like to know how to put a time delay in a Python script.


Is it possible to typeset complex chemical structures such as the structure for carboxylic acid or aromatic compound using mhchem?

Can you create diagrams of chemical structures in LaTeX?   Example(s) of "chemical structure diagrams":


Prove that the space of all $m*n$ matrices over the field  $F$ has dimension $mn$, by exhibiting a basis for this space.  I know that it is too easy to prove but cannot remember any basis for this space. please help me.

I am reading Hoffman & Kunze's chapter on linear transformations, with a view towards understanding dual spaces. (I primarily want to read Calculus on Manifolds; in the first chapter of that book, Spivak marks one exercise concerned with dual spaces as "soon-to-be-important". I never studied dual spaces in my linear algebra course, and I want to be sure I follow his development.)   H&K state the theorem that the space of linear transformations $L(V, W)$ from $n$-dimensional $V$ to $m$ dimensional $W$ has dimension $nm$. I am having a hard time understanding their proof; they basically just juggle $\Sigma$-notation. I somewhat follow the steps, which loosely are as follows: you let $\mathcal{B} = \{\alpha_1, ... \alpha_n\}$ be a basis for $V$, and $\mathcal{B'} = \{\beta_1, ... \beta_m\}$ a basis for $W$. For $1 \leq p \leq m$, $1 \leq q \leq n$, define  $$E^{(p,q)} : V \to W : c_1\alpha_1 + ... + c_q\alpha_q ... +c_n\alpha_n \to c_q\beta_p;$$  that is, let   $$E^{(p,q)}(\alpha_i) =     \left\{      \begin{array}{}        0, & i \neq q \\        \beta_p, & i = q       \end{array}    \right.$$  and put $E^{(p,q)}(\gamma) = \sum_{i=1}^n c_iE^{(p,q)}(\alpha_i).$ Fix some arbitrary l.t. $T: V \to W$ such that  $$T(\alpha_i) = \sum_{p=1}^m A_{(p,i)} \beta_p = A_{(1,i)}\beta_1 + A_{(2,i)}\beta_2 + ... +A_{(m,i)}\beta_m$$   for some weights $A_{(1,i)}, A_{(2,i)}, ... A_{(m,i)}, 1 \leq i \leq n$. Now consider   $$ T'(\gamma) := \sum_{p=1}^m\sum_{q=1}^nA_{(p,q)}E^{(p,q)}(\gamma).$$  On the one hand,  \begin{align} T'(\gamma) = \sum_{p=1}^m\sum_{q=1}^nA_{(p,q)}E^{(p,q)}(\gamma) &= \sum_{p=1}^m\sum_{q=1}^nA_{(p,q)}E^{(p,q)}(c_1\alpha_1 + ... + c_q\alpha_q ... +c_n\alpha_n)\\ & = \sum_{p=1}^m\sum_{q=1}^nA_{(p,q)}c_q \beta_p\\ & = \sum_{p=1}^m (\sum_{q=1}^nA_{(p,q)}c_q) \beta_p \end{align}  On the other hand,  $$ T(\gamma) = \sum_{i=1}^n c_iT(\alpha_i) = \sum_{i=1}^n c_i\sum_{p=1}^m A_{(p,i)}\beta_p = \sum_{p=1}^m(\sum_{i=1}^nc_iA_{(p,i)})\beta_p$$  so $T' = T$. Then you show that all the $E^{whatever}$ are linearly independent, and you are "done".    The problem with this is that I have no idea what's going on here. When I focus, I can make sense of the $\Sigma$-notation, but otherwise I don't follow the proof. So, I have to ask:   What is the intuition for why the theorem is true? Can anybody make the proof given more intuitive? (For example, what are the $E^{whatever}$ really doing? How did H&K know that we'd have $T' = T$ (how did they think of $T'$)?


Let $\mathbb{M_n(\mathbb{R})}$ denote the set of all $n\times n$ matrices with real entries (identified with $\mathbb{R}^{n^2}$ and endowed with its usual topology) and let $GL(n;\mathbb{R})$ denote the group of invertible matrices. Let $G$ be a subgroup of $GL(n;\mathbb{R})$. Denote $$H=\left\{A\in G~~\bigg|~~\begin{array}{}\exists~\varphi:[0,1]\rightarrow G~\text{continuous}\\ \text{such that}~\varphi(0)=A,\varphi(1)=I\end{array}\right\}$$ How can I show that $H$ is a normal subgroup of $G$?

Let $M(n;\mathbb{R})$ denote the set of all $n \times n$ matrices with real entries (identified with $\mathbb{R}^{n^{2}}$ and endowed with its usual topology) and let $GL(n;\mathbb{R})$ denote the group of invertible matrices. Let $G$ be a subgroup of $GL(n;\mathbb{R})$. Define $$H = \biggl\{ A \in G  \ \biggl| \ \exists \ \varphi:[0,1] \to G \ \text{continuous such that} \ \varphi(0)=A , \ \varphi(1)=I\biggr\}$$  Then is $H$ normal in $G$?  For proving $H$ normal i should verify two things:   First $H$ is a subgroup. For all $A \in G, B \in H$, we must have $A \cdot B \cdot A^{-1} \in H$.   That's it i  am not able to proceed any further.


I have tried searching for ways to create android apps using python but I haven't found any, is there any way to do so. I found kivy but no place shows how to convert it to a file.

We are working on an  version and this platform has a nice Python API..  However, there is nothing official about Python on Android, but since  exists, is there a way to let the snake and the robot work together??


Currently i am in the process of removing bad inbound links towards my website. Now apart from PR or domain related significance how i know that which inbound links are passes the good link juice for my site.  Is it there any qualitative approaches in this direction?

I have been reading Webmasters SE and many other blogs on this topic but I could not understand how do we truly evaluate a bad link that we must disavow in GWT. Everybody seem to have a different opinion on this.  A little background  I am a WordPress developer and 3 years ago I gave away a WordPress theme to my blog visitors which has a dofollow link back to my business website. Like this.  WordPress theme designed by MyBusinessName   From last 2 years I was not paying any attention on organic traffic to my business website because of other projects.  That free WordPress theme helped us getting ~10K backlinks from variety of domains and websites. All most 99% backlinks are from non-related websites and in many different languages.  Now  Last week it came to my attention that in October 2013, organic traffic from Google started decreasing and in just 2 months it became as low as 25% of October. Before October it was gradually increasing ~5-10% per month.  So I researched and draw to the conclusion that it could be because of Penguin Update. Since  was introduced at the same time.  Now I need information on what a bad/toxic link is.  I was about to disavow almost all links but after reading many topics on Webmasters SE I think I need more information on how to identify a bad link.   Does credit link in footer consider as spam because it build thousands of backlinks? Do foreign language website backlinks consider as spam? Should I remove all backlinks from theme users because almost all are from non-related content domains? Although some links from non-related content domains have nice DA/PA. Should I remove those too? I understand foreign language anchor text backlink could be a spam but what if it is from related foreign language content.   The question is how exactly one can find a link that is bad and must be removed.


My UK visa refusal letter came back without a specific reason for refusal that I can rectify the next time am applying and for the record I don't see any reason for refusal coz I provided both my father and the other sponsor's official employment letters , pay slips and bank statements covering the last six months. My father takes care of me here in my home country where we both leave and my other sponsor who is my aunt is UK citizen and she was the one supposed to care of me in UK as she stated in the invitation letter and the sponsorship under taking form. Am a full time university student so I don't work, I provided my university enrollment certificates and a letter from the dean stating I was free to travel because its the official university holidays given that I come back in time when studies resume so that I can finish my third and final year Am always in touch with my aunt coz she usually visits us here and we regularly chat so I also provided screenshots of our WhatsApp chats I show that we keep in touch. So I don't know the exact reason why my application was refused that I can rectify the next time I apply. They only told me the change the circumstances of my application and check Appendix V

I received my refusal letter today for my standard visitor visa application for the UK. However, the reason for refusal is not mentioned anywhere on the letter and it appears more of an unfilled template. How may I proceed after this? Do I contact them and how do I do that? or should I just reapply? I am currently living in Egypt.  Please check the attached letter.


I'm trying to install Ubuntu one from the software center but when I'm trying to install it, it opens a page saying not found. is there any terminal command to install Ubuntu one?

I have purchase new laptop from Dell with ubuntu 12.04 preinstalled. while connecting to Ubuntu One following occurs and I am not able to sync with Ubuntu One.   WebClientErr u'Error downloading https://one.ubuntu.com/api/account/ - server replied:Not       Found' u'<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">\n \n<title>404 Not Found</title>\n\n
 Not Found
\n
The requested URL /api/account/ was not found on this server.
\n
\n<address>Apache/2.2.22 (Ubuntu) Server at one.ubuntu.com Port 443 </address>\n\n'


I am using Ubuntu 14.04.2 LTS. Sometimes Ubuntu freezes and i can't do anything anymore.  What can i do to recover from this situation? In windows it was simple i just had to use task manager via alt+ctrl+delete. Is there something like this in Ubuntu? I know that there is xkill and System Monitor in Ubuntu but when Ubuntu freezes i can't use any of them and i can't open terminal and even though i have set a shortcut for xkill but still after freezing happens i can't use xkill. It's like after freezing nothing works.

All operating systems freeze sometimes, and Ubuntu is no exception. What should I do to regain control when...   just one program stops responding? nothing at all responds to mouse clicks or key presses? the mouse stops moving entirely? I have an    In what order should I try various solutions before deciding to pull the power plug?  What should I do when starting up Ubuntu fails?  Is there a diagnostic procedure I can follow?


1) I wish to have the arrow indicator to be in the center rather than touching the edge of the flowchart shapes. Is there a possibility to do so?  2) The connection between CCC ->> DDD; CCC->>FFF and CCC->>HHH should be as indicated in the image.   Thanks for your assistance.  \documentclass{amsart}  \usepackage[latin1]{inputenc} \usepackage{tikz} \usepackage[margin=1in]{geometry} \usetikzlibrary{shapes,arrows,calc}  \begin{document}  \tikzstyle{startstop} = [ellipse, rounded corners, minimum width=3cm, minimum height=1cm,text centered, draw=black, fill=red!30] \tikzstyle{io} = [trapezium, trapezium left angle=70, trapezium right angle=110, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=blue!30] \tikzstyle{process} = [rectangle, minimum width=4cm, minimum height=1cm, text centered,text width=3cm, draw=black, fill=orange!30] \tikzstyle{decision} = [diamond, minimum width=1.5cm, minimum height=0.5cm, text centered,text width=1.5cm,draw=black, fill=green!30] \tikzstyle{arrow} = [thick,->,>=stealth] \tikzstyle{line} = [thick,->,>=stealth]   \begin{figure} \centering \begin{tikzpicture}[node distance=2.5cm,scale=0.75,transform shape,font=\normalsize] \node (start) [startstop] {Start}; \node (pro1) [process, below of=start] {AAA}; \node (pro2) [process, below of=pro1] {BBB}; \node (pro3) [process, below of=pro2] {CCC}; \node (pro4) [process, below of=pro3,xshift=-2cm] {DDD}; \node (pro4c) [process, left of=pro4,xshift=-2.5cm] {EEE}; \node (pro4a) [process, right of=pro4,xshift=2cm] {FFF}; \node (pro4b) [process, right of=pro4a,xshift=2.5cm] {GGG}; \node (pro5) [process, below of=pro4,xshift=2cm] {HHH}; \node (pro6) [process, below of=pro5] {III}; \node (pro7) [process, below of=pro6] {JJJ}; \node (pro8) [process, below of=pro7] {KKK}; \node (pro9) [process, below of=pro8] {LLL}; \node (dec1) [decision, below of=pro9,yshift=-1cm] {MMM}; \node (pro10) [process, right of=pro3,xshift=2.5cm] {NNN}; \node (stop)[startstop, below of=dec1,yshift=-1cm] {stop};  \draw [arrow] (start) -- (pro1); \draw [arrow] (pro1) -- (pro2); \draw [arrow] (pro2) -- (pro3); \draw [arrow] (pro3) -- (pro4); \draw [arrow] (pro3) -- (pro4a); \draw [arrow] (pro4c) -- (pro4); \draw [arrow] (pro4b) -- (pro4a); \draw [arrow] (pro4) -- (pro5); \draw [arrow] (pro4a) -- (pro5); \draw [arrow] (pro5) -- (pro6); \draw [arrow] (pro6) -- (pro7); \draw [arrow] (pro7) -- (pro8); \draw [arrow] (pro8) -- (pro9); \draw [arrow] (pro9) -- (dec1); \draw [arrow] (dec1) -- node[anchor=east] {YES}(stop); \draw [arrow] (dec1) -- ($(dec1)+(10,0)$) coordinate (x); \draw [arrow] (x)--(x|-pro10) node[midway,right] {NO}--(pro10); \draw [arrow] (pro10) -- (pro3); \end{tikzpicture} \caption{XXXXXXXXX} \label{fig:my_label} \end{figure}   \end{document}


I tried to uncompress a zip file but I get error  “The compressed (zip) folder is invalid or corrupted”.   Is it possible to get virus just by trying to uncompress the zip? Can zip extension be manipulated so it is not actually a zip file but a virus?

Can files be infected with malware and them running as soon as the disk their on is connected/when their opened(Im talking for files like mp4/mov/avi, pngs(images generally) and compressed zip,tar.gz and most of all text files files)  If so is there any reliable way to check if they are infected


I am facing some issue with PDP MySQL, I am trying store records in multiple languages, I set charset as UTF8 for all(PHP,MYSQL,PDO), still I am facing issue, the records updating as like below  Steps I followed:   Set UTF for MySQL DB Set UTF8 for MySQL table Set UTF8 for PDO (PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'") SET UFT8 for PHP output   But still facing the issue, how ever I can insert/update in phpmyadmin manually without any issue.  Please help me to resolve this.  Thanks, Ashok

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


Is it possible to track the event when a user manually locked the station (by pressing Windows + L) in event viewer or in the registry?   I am using Windows 7 Home Premium 64 bit.

Is there a way to get a list of the following times:  whenever windows is locked (using windows+l combo)  whenever windows is unlocked in the past week?   I've tried poking in the event log, to no avail. Many thanks!


In short, I need to nuke it from orbit (Which seems to be the preferred method)  But how? Is there a package I can use, or do I just rm -rf / like a noob?  I'll point out now that rm -rf / does very Little damage do a chunk of Linux, so probably is more of a Missile strike than nuke.  THIS QUESTION WILL BE WIKI'D WHEN I GET TO IT. So, post all the crazy and fun methods you have.

How can I destroy my Ubuntu system (in a virtual PC) or render it unbootable?


I know that the force is used to change the direction of the velocity but my question is while it has 3 options either to pull the object towards the center or change the direction of velocity or both. It would have been more appropriate if it did both.

Why doesn't the Moon fall onto the Earth? For that matter, why doesn't anything rotating a larger body ever fall onto the larger body?


$T(0)=1 \\ T(n) = 1 + \sum_{j=0}^{n-1}T(j) \\ $  Show that $T(n) = 2^n$.  I know how to prove this by induction, but I would like to know how to show this using first principles.  Edit: The way I want to solve this problem is manipulate $T(n)$ in such a way that it ends up as $2^n$.

Show that  $$t(n) = 1 + \sum_{ j=0}^{n-1} t(j)$$  is the same as  $$t(n) = 2^n$$  Initial condition $t(0) = 1$


How to prove that the $\{$ fractional part of $n\alpha\mid n \in \mathbb{N}$ $\}$ is dense in $[0,1]$ for an irrational number $\alpha$.   NOTICE that $n$ is in $\mathbb{N}$ Also notice that this is not a duplicate of the mentioned question as it does not carry a correct answer and the partially correct answer in the said question is given for integer multiple case, NOT for $n \in \mathbb{N}$

Let $x\in \mathbb{R}$ an irrational number. Define $X=\{nx-\lfloor nx\rfloor: n\in \mathbb{N}\}$. Prove that $X$ is dense on $[0,1)$.    Can anyone give some hint to solve this problem? I tried contradiction but could not reach a proof.  I spend part of the day studying this question   and its answers. Only one answer is clear and give clues to solve the problem. This answer is the first one. However, this answer does not answer the question nor directly, nor the proof follows from this answer.   This answer has some mistakes, he use that $[(k_1-k_2)\alpha]=[k_1\alpha]-[k_2\alpha]$ which is not true. Consider $k_1=3, k_2=1, \alpha=\sqrt{2}$ we have $[(k_1-k_2)\alpha]=2\not= 3=[k_1\alpha]-[k_2\alpha] $. We only can assure that $[k_2\alpha]-[k_1\alpha]-1\leq [(k_2-k_1)\alpha]\leq[k_2\alpha]-[k_1\alpha]$.   Who answered said something interesting about additive subgroups of $\mathbb{R}$, but unfortunately the set $X=\{nx-[nx] : n\in \mathbb{N} \}$ is not a subgroup. Considering the additive subgroup $G=\langle X \rangle$, if we prove the part (a) of the link, we get that indeed $G$ is dense on $\mathbb{R}$ but we can not conclude that $X$ is dense on $[0,1)$.  I think this problem has not been solved.  Thanks!


I've been stressing out for a few hours now trying to get my project to compile. I was originally using Overleaf but my project got too big to compile and so I'm now attempting to compile it using Texmaker.  On Texmaker when trying to quick build, I get warnings that all of my citations are undefined and my bibliography is empty. I am fairly certain Texmaker sees my bibliography file as I've directed which folder to look in.   Here's my main file shortened to the important bits:  \documentclass[11pt]{article} \usepackage[utf8]{inputenc} \usepackage[british]{babel} \usepackage{csquotes} % Removes babel warning.  \title{\vspace{-5ex}Title} \author{} \date{\vspace{-15ex}}  \usepackage[style=ieee,sorting=none,citestyle=numeric,url=true]{biblatex} \addbibresource{sections/bib.bib}   \section{Project Definition} \input{sections/definition.tex}  \section{Project Justification} \input{sections/justification.tex}  \section{Key Literature} \input{sections/literature.tex}  \section{Project Plan} \input{sections/plan.tex}  \clearpage  \sloppy \printbibliography[title=References]  \end{document}

Running the minimal example  \documentclass{article} \usepackage{filecontents} \begin{filecontents*}{\jobname.bib} @ARTICLE{example,   author  = {Other, Anthony Norman},   title   = {Some things I did},   year    = {2014},   journal = {J.~Irrep. Res.},   volume  = {1},   number  = {1},   pages   = {1-10} } \end{filecontents*} \usepackage[backend=biber]{biblatex} \addbibresource{\jobname.bib} \begin{document} Hello\cite{example}. \printbibliography \end{document}   I get the warning There were undefined references.  I have read  and know that I need to run:   LaTeX Biber LaTeX   However, my editor is only set up to run BibTeX. How do I go about setting up my editor/IDE to be able to run Biber, and how do I run the LaTeX/Biber/LaTeX cycle?  Answers (sorted alphabetically by editor name)                    Answer guidelines   Each answer should be for one editor. If the editor is cross-platform, if possible give a single answer with notes covering the minor platform variations. Please edit the question to include new answers in the 'link list' Each answer should be 'stand alone', i.e. don't say 'It's almost the same as editor Y but ...' for the editor part Instructions for 'build tools' such as arara or latexmk are welcome but should explain how to set up the editor in question as not all editors allow simple addition of arbitrary tools


I am having two batteries of different specs (both, dry cell, UPS/inverter batteries)  Battery A: 12 V, 26 Ah  Battery B: 12 V, 7.2 Ah  I need a 24 V output so I have connected them in series.  My question is, will it damage my batteries?  If the configuration is okay, can I charge the 12 V 26 Ah battery alone? Wouldn't it push a higher current to battery A and keep the voltage at a steady state?  I don't have a 24 V charger, but I do have a 12 V charger. Yes I can charge them both parallely but I don't want to do that as I would have to open up my robot to access the batteries.  P.S. Sorry if it's a silly question. I am not much of an expert in this.

I have a 1.5 amp-hour, 12 V battery and I have a 10 amp-hour 12 V battery. I know the voltage will increase to 24 V when they are put in series, but I don't know what goes on amp-hour wise.   Does the new amp-hour rating take the amp hour of the low amp hour rating, does it take the 10 amp hours or is it like an average?


I'm trying to make the setInterval clear when a user types in the off command, how would I go about doing this? Basically, the user types the on command then then turn it off using the off command. This is a snippet of what I currently have.   bot.on('message', (message) => {      if (message.content.startsWith(prefix + 'on')) {         var check = setInterval(test, 5000);       } else if (message.content.startsWith(prefix + 'off')) {         clearInterval(test);      }      function test() {     console.log('hello');      } }

What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?


I am trying to generate the triple integral in the following equation (The preamble is large, due to other requirements)  \documentclass[11pt,headings=small,fleqn]{scrreprt} % highest level is chapter %\documentclass[12pt,journal,compsoc]{report} \usepackage[Glenn]{fncychap} %To add a rectangle at the beginning of each chapter \usepackage[greek,english]{babel} % for English text only %\usepackage[ngerman]{babel} % for German text only %\usepackage{ngerman}        % for German text only \usepackage{mathtools}    %To split equations \usepackage{amsmath} \usepackage{esint} \usepackage{mathdesign} \usepackage[ansinew]{inputenc} \usepackage[T1]{fontenc} \usepackage{rotating} \usepackage{multirow} \usepackage{microtype} % improves font spacing, needs pdfTEX >= 1.20 \usepackage{hyperref}  % hyperlinks  \usepackage{graphicx} \usepackage{subfigure}  \usepackage{makeidx}     \begin{flalign}     \frac{\partial}{\partial t}\oiiint \rho dv + \oiint \rho \stackrel{\rightarrow}{V}\cdot \stackrel{\rightarrow}{ss}=0     \end{flalign}   But I keep getting the error undefined control sequence \oiiint  Can any one help please?

I am using LyX with MikTeX and I am trying to use the following command \oiiint but I am getting the following error:   \oiiint  The control sequence at the end of the top line of your error message was never \def'ed. If you have misspelled it (e.g., `\hobx'), type `I' and the correct spelling (e.g., `I\hbox'). Otherwise just continue, and I'll forget about whatever was undefined.   I have added \usepackage{mathdesign} to the preamble in:  Document -> Settings -> LaTeX Preamble  Why is this not working?


I had a question, nobody else posted any answers, and I worked out the solution myself.  Why do I have to wait 24 hours to accept my own answer. When I don't have to wait before accepting anybody else's answer?

I have read all the discussions around the 48 hour delay on accepting ones own answers. To quote Jeff Atwood:  You must wait 2 days from the time you originally asked your question before you can accept your own answer. This gives other users a chance to answer the question in good faith, and earn the accepted answer.  Let's suppose you ask a question. You finish typing it out, but don't press Post Your Question. Instead, you go off and do a bit of research. You find a solution. Instead of discarding the question, you decide to share your new knowledge with the community because you're just that type of person. So you check Answer your own question after reading that it is . You enter your answer and submit both the question and answer. Knowing that your answer solved the problem, you try to accept your own answer to indicate as much to everyone. You are then confronted with  You can accept your own answer in 2 days.  Now, your intention is to come back in two days and accept your answer. You come back two days later, but in the meantime, others have provided answers in the hope of getting accepted. However, your intention has always been to accept your own answer because you know it is correct. You have just lured them into wasting their time providing answers that you already know will not be accepted. You accept your own answer and that's that. But not quite... you get annoyed when you realise that your effort to share knowledge has been sabotaged by your correct answer not appearing at the top. Can we have the system changed to work like this:  Provide an additional "Answer and accept your own question"; Always keep the accepted answer at the top, no matter whose answer it is; Don't count votes on the question or answer toward the user's reputation. If the user decides to accept another person's answer after the fact, allow votes on the question only to affect the user's reputation.  If you're going to say that you encourage users to ask and answer their own question, you should not sabotage their efforts to do so by demoting their answer. It's just pointless. You already have measures in place to prevent gaming, such as not counting the answer towards the user's reputation.


For an add-on I'm working on, I followed  to create a simple UIList. It looks like this:  This works rather nicely, except that I'd like the PropertyGroup properties OpenRoof and Furnished (in red squares, above) to display their values in columns next to each object's name in the list (e.g., in the empty squared locations in my JPEG). Currently, I can only see/edit these properties' values by specifically selecting an object. I've looked through the Python API documentation for UIList but it was not clear to me if there is a way to do this.  Can the UIList display be altered to behave like I've described?

How can I make a Interface which is similar to the Material-Interface within Blender via Python?    It should look like these. Could you guide me to the right direction? I don't think it's in bpy.ops, right?  Thank you very much!


The conspiracy theorist hat in Winter Bash is awarded on total number of flags or the flags done after the start of Winter Bash.?

Description of the hat unlock requirement:     at least 5 flags dismissed as helpful and at most 20% of non-disputed flags declined   Does "dismissed" mean something unusual here, or is this hat not unlocking properly? I'm not sure if that means "since winter bash started" or "since your account was created": if the former, I've flagged 8 items so far today, of which 6 were marked "helpful" (the other two are still active; none have been disputed or declined). If the latter, the flag page indicates I've flagged 391 items (plus 6 for spam), of which 1 was declined (which incidentally, I assume that was by accident, given that the question was closed soon after for the reason I flagged it for), 1 was disputed (that one was legitimate), and 21 are still open. That is definitely way under 20%.  So what's up with that unlock?  edit: it appears to be the case (further edit: this has now been confirmed first-hand) that this hat unlock disregards any flags that are the flag equivalent of voting to close. I put forth that if this is intended behavior, well, it shouldn't be (if it's to equalize the playing field for over-3k-rep people, it should just also count votes-to-close. Though granted, I suppose in the scheme of things it really doesn't matter much, as it'll all go away in a couple weeks anyway. But dang it, I want to show off all the flagging I do! :p)


This is my C code:  #include <stdio.h>  void print_hello() {     printf("Hello n10321234, welcome to BSB211"); }  int main() {     print_hello();     return 0; }   However, I keep getting the following errors when I compile and run the executable.  ./print_hello: line 3: syntax error near unexpected token ('  ./print_hello: line 3: `void print_hello(){'   For compiling, I use gcc print_hello.c -o print_hello  and to run I use ./print_hello.

I am trying to learn C++, but I can't even make the first (hello world) example from cplusplus.org work with g++ command or c++. I created a file just like the example and ran g++ myfile, then ./myfile.  I get a permission problem, then I use chmod +x myfile and the permission problem is gone but this problem happens:  gzuspower@gzuspower:~/Desktop$ ./4 ./4: line 1: //myfirst: No such file or directory ./4: line 4: syntax error near unexpected token `(' ./4: line 4: `int main ()'   I called my file 4 because it is my 4th attempt. This is on Xubuntu 16.04.The duplicate question answer did not work i tried .c ,.cpp ,as file extension and tried firstc++ (my first attempt file) instead of 4(my fourth attempt file) and nothing works. i'm going to try different form of hello-world code.


What happens when I flag a posted answer as not an answer? Is the answer put into a review queue? Or will it be deleted?

What is the "Not an Answer" flag and what is its purpose? When should I use this flag? When should I not use this flag? But I'm still not sure if I'm using the flag correctly... An answer is "Not an Answer", but the flag was declined or disputed!   See also:


I am trying to convert an array of floats to strings, but I am running into an error where the string array ends up slightly different from the original float array.  I am using the numpy.arange function to create my list of floats, and then using a basic for loop to convert the next float to a string and append it to a string array.  However, the results are not as expected.   hue_order = []  for i in np.arange(0.375,0.625,0.025):     hue_order.append(str(i))   Expected result:  ['0.375',  '0.4',  '0.425',  '0.45',  '0.475',  '0.5',  '0.525',  '0.55',  '0.575',  '0.6']  Actual result:  ['0.375',  '0.4',  '0.42500000000000004',  '0.45000000000000007',  '0.4750000000000001',  '0.5000000000000001',  '0.5250000000000001',  '0.5500000000000002',  '0.5750000000000002',  '0.6000000000000002']  Seems like some sort of numerical instability issue but I am not sure how to resolve it.

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


The question is:   A capacitor of capacitance C1 is connected to a battery of potential V0. The battery is then disconnected and a second capacitor of capacitance C2 is connected to the first capacitor. The new potential of the capacitors is V. Express C2 in terms of C1, V0 and V.   I made two approaches.   At first I used charge conservation. If q is the charge of the first capacitor, then after the second capacitor is connected, q will be distributed among them. If q1 and q2 are charges of capacitor 1 and 2, respectively, then $q = q_1 + q_2$. Using this,  I got $$C_2 = C_1*\frac{V_0-V}{V}$$ My second approach was using energy conservation. Before capacitor 2 was introduced, the energy saved in capacitor 1 was $E = \frac{1}{2}C_1V_0^2 $. Afterwards, the energy saved in each capacitor is given by,  $E_1 = \frac{1}{2}C_1V^2$ and $E_2 = \frac{1}{2}C_2V^2$. If I assume $E = E_1 + E_2$, I get $$C_2 = C_1*\frac{V_0^2-V^2}{V^2}$$   Why am I getting two different expressions? The energy I began with doesn't seem to be the energy I ended up with. Why is that?

A capacitor is charged. It is then connected to an identical uncharged capacitor using superconducting wires. Each capacitor has 1/2 the charge as the original, so 1/4 the energy - so we only have 1/2 the energy we started with. What happened? my first thoughts were that the difference in energy is due to heat produced in the wire. It may be heat, or it may be that this is needed to keep equilibrium.


After I enter the command sudo apt-get install git The password field pops up but takes no input

When I'm about to install a program in the terminal it wants the password:  [sudo] password for xxx:   But when I start to type my password nothing happens. What should I do?


Supposing I am in a non-inertial system and I don't know what forces are acting. How  can I test EXPERIMENTALLY and in practice to be in a non inertial system? If I am in a system and I don't know how does it moves and I would make an experiment to test if this is inertial or not, what should I do? For example: in a lift? In a rotating system?

I understand that you can (in principle) measure whether "free particles" (no forces) experience accelerations in order to tell whether a frame is inertial. But fundamentally, what determines which frames are inertial (i.e. what principle selects in which frames free particles will not appear to accelerate)? I've been told that the cosmic microwaves determine the ultimate rest frame of the universe, but that doesn't make sense to me, since one can still ask why that frame is an inertial frame.  Also, I understand that there are no real inertial frames in general relativity, but it seems like there certainly exists approximate inertial frames and we can ask why those frames are approximately inertial and not others. For example, in the frame of a person riding a merry go round, free particles appear to greatly accelerate; while in the frame of someone standing next to the merry go round there are no such great accelerations. Why does the guy (or gal) on the merry go round see free particles accelerating while the other guy doesn't.   And if you're gonna tell me that it's "the rest of the stuff in the universe" that determines whether the person on the merry go round sees free particles accelerate, I'll ask how you know that all that stuff is not spinning.  I hope this question sort of makes sense, it's been bothering me for a while and my study of relativity (most of special relativity and just the outline of general relativity) hasn't really clarified it for me much.


Given that $x, y, z$ are positive integers and that $$3x=4y=7z$$ find   the minimum value of $x+y+z$. The options are:      A) 33      B) 40      C) 49      D) 61      E) 84   My attempt:  $y=\frac{3}{4}x, z=\frac{3}{7}x$.    Substituting these values into $x+y+z$, I get $\frac{117}{28}x$.  I have no idea how to continue.  $x$ in this case would have to be 28, meaning that the sum is $117$, which is not one of the options

If $x$, $y$ and $z$ are positive integer and $3x=4y=7z$, then What is the least possible value of $x+y+z$?


Fairly new to regex, looking to identify a user id pattern that is all alpha, is exactly 6 characters, and the second character is always a Z.  Any help would be appreciated.

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


This question has been asked before and I have read the answers, but they do not seem to work for me.  The simplest answer seems to be to use chsh.  Makes sense!  But when I do sudo chsh -s tcsh rolf I get a warning "tcsh does not exist".  Yet if I type which tcsh I get /usr/bin/tcsh and if I type tcsh at the command line I get a tcsh shell.  If I just do sudo chsh rolf I get an interactive result that indicates that tcsh already is my login shell.  Nevertheless whenever I log in, I  get a bash shell (until I take overt action by typing tcsh).  What can I do to get tcsh as my shell automatically?  (Please don't tell me that I should be using bash and not tcsh; that is not an issue which I am disposed to discuss.)

I want to change the default shell of Terminator to zsh. In /etc/passwd/ I've changed the default shell to /bin/zsh. This settings changes the default shell in LXTerminal (the default terminal on Lubuntu), but not in Terminator. So I tried chsh -s /bin/zsh, but that doesn't work either. The Terminator  says:  How do I change my default shell? Terminator will always start the shell specified by the SHELL environment variable. (It will fall back to /bin/sh if the SHELL environment variable isn't set.) You could simply influence Terminator's environment, but the best solution is to tell your operating system which shell you'd like, and it will ensure that SHELL is set correctly for all applications, not just Terminator. See the documentation for your operating system for details on how to change your default shell.  So I expected my attempts to work, but they don't. How can I change the default shell in Terminator.


I have this program in C.  #include <stdio.h> #include <string.h>  char * pwd = "pwd0";  void print_my_pwd() {   printf("your pwd is: %s\n", pwd); }  int check_pwd(char * uname, char * upwd) {   char name[8];   strcpy(name, uname);    if (strcmp(pwd, upwd)) {     printf("non authorized\n");     return 1;   }   printf("authorized\n");   return 0; }  int main(int argc, char ** argv) {   check_pwd(argv[1], argv[2]);   return 0; }   I build it and examine it for buffer overflow.   $ make gcc -O0 -ggdb -o main main.c -fno-stack-protector $ gdb main GNU gdb (Ubuntu 8.2-0ubuntu1~18.04) 8.2 Copyright (C) 2018 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at:     <http://www.gnu.org/software/gdb/documentation/>.  For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from main...done. (gdb) b check_pwd Breakpoint 1 at 0x76c: file main.c, line 12. (gdb) run joe f00b4r42 Starting program: /home/developer/main joe f00b4r42 [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".  Breakpoint 1, check_pwd (uname=0x7fffffffdc01 "joe", upwd=0x7fffffffdc05 "f00b4r42") at main.c:12 12    strcpy(name, uname); (gdb) info frame Stack level 0, frame at 0x7fffffffd6d0:  rip = 0x55555555476c in check_pwd (main.c:12); saved rip = 0x5555555547ef  called by frame at 0x7fffffffd6f0  source language c.  Arglist at 0x7fffffffd6c0, args: uname=0x7fffffffdc01 "joe", upwd=0x7fffffffdc05 "f00b4r42"  Locals at 0x7fffffffd6c0, Previous frame's sp is 0x7fffffffd6d0  Saved registers:   rbp at 0x7fffffffd6c0, rip at 0x7fffffffd6c8 (gdb) p &name $1 = (char (*)[8]) 0x7fffffffd6b8 (gdb) p &print_my_pwd $2 = (void (*)()) 0x55555555473a <print_my_pwd> (gdb) Quit A debugging session is active.      Inferior 1 [process 21935] will be killed.  Quit anyway? (y or n) y $ ./main $(python -c "print 'AAAAAAAAAAAAAAAA:GUUUU'") B non authorized your pwd is: pwd0 Segmentation fault (core dumped) $    So it was possible to leak the secret from the program but what could I do if the address would have been 0x55555555003a instead of 0x55555555473a ? Then I would not know how to pass the zero because it would be represented as a null byte and the shell would not interpret that.

So I'd like to pass the first 512 bytes of binaryFile.dd as the second parameter to myProgram but bash strips out all the NUL chars. Is there any way to avoid this in bash or am I on a hiding to nothing?   myProgram parameter1 "$(head -c 512 binaryFile.dd)"


What is the exact rule regarding the plural/singular 'year'?  Which one is correct and why:   A five-year degree A five-years degree   As in a degree that takes five years to complete, of course.  Furthermore do you capitalize any word, and is it proper form to use numerals (5-year(s))?

So I was taught that you should almost always use singular form of an adjective instead of plural form. But recently, I've seen people using plural form and it sounds quite weird and I don't know if it is correct.  For example,   "Salary tax" instead of "Salaries tax" "Office supplies" instead of "Offices supplies" "Product demo" instead of "Product demo"   In the above cases, the word "Salary" is used as an adjective to describe the type of "tax", so it will be in singular form. But I saw people using salaries tax and not sure if it is grammatical.  So my question is if there are any general rules on how to use the singular/plural form of an adjective?


Maybe I'm missing something obvious, but is there documentation on the SEDE schema anywhere? As listed here , it's not obvious what all the fields are. I've had a root around, but can't find anything.

Stack Exchange releases "data dumps" of all its publicly available content roughly every three months , and also makes that information queryable over the Internet at the  (SEDE) (updated weekly, on Sunday). Over time, as new features and other bits of data are introduced to Stack Exchange sites, the "anatomy" of the data dump is likely to change.


I seem to be unable to tolerate Parmesan cheese (not the processed "parmesan-flavored" cheese, but the real Italian Parmesan) - as a topping it makes me gag, and if included in a recipe either nauseates me or gives me a stomach ache.  I have no trouble with Romano, Asiago, Auribella, etc.  Just the Parmesan.  What cheese (or combination of cheeses) could I substitute for Parmesan in most recipes and still get a good result?  thanx much!

The parmesan cheese in pasta recipe is quite expensive.....do we have cheaper alternative??  Are there are cheddar cheese which can replace parmesan cheese?


Maybe a button can be implemented into the menu to see the revision history for a question or answer?

I find revisions a really useful way to see full edit history of every post in Stack Exchange.  Can we please have it on the iOS app too? It will also let us see original time of the post submission which is missing, currently showing only last edit time.


It's hard to explain the situation in title, so here it is:  I'm booking a 2 ways tickets from Singapore to Vietnam (Hanoi). However, i didn't board the trip Sing-Viet. Instead, I purchased another 1 way ticket, from Singapore to Vietnam with different time.  In that case, when I'm back from Vietnam to Singapore, the flight counter said, my tickets is not valid anymore, as i didn't take the 1st board,     Based on International Rules, they said.   So, Is my 2 ways tickets valid?

I was browsing flight price at Singapore Airlines website, and a one-way flight from SIN to SFO cost this much:    That's quite expensive. I tried browsing around and found that a return flight from SFO to SIN and back to SFO cost much cheaper:    It's really weird because the second ticket includes the exact same flight that cost 1900+, but it's almost half the price. The reason for this counter-intuitive situation is explained in the answers this question   If I am located in Singapore and my intention is to fly one-way to SFO, is it safe to book the flight in the second picture and only board SFO-SIN leg? Will they deny me because I miss the SIN-SFO flight?


What's the diffeernce between super(SomeClass, self).__init__() AND super(SomeClass, self).__init__(*args, **kwargs)? The first one initializes the constructor of the parent, but what about the second one?

In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2):


10-15 years ago I read a comic book about an astronaut. As far as I remember the action begin on Earth right after some kind of war or conflict with alien race. Main hero is young or middle aged man who works as astronaut. He is traveling through space and due to some physics factors (speed? gravity?) his time passes slower than on Earth. I don't remember too much, just few scenes:   He goes back on earth and someone from his family (maybe mother, not sure) is dying, he can't get any medicines due to some regime policy, he is trying to buy it on black market or something like that. He lose his limbs and he is on some "spa"-like planet where it grows back. Some people in future don't have sex (maybe they are androids?). I'm not sure how many years it takes (the action) but I think it may be like 300-1000 years from the beginning to the end, I think it was more than one book.

I remember only last part of comic book:   There is a scene of attack (in space) against aliens, hero is flying space shuttle. He return to active duty, there is a war with enigmatic aliens, after hospital he is trained in virtual reality environment Main planet of aliens is spotted and humans send ship against it, journey in one direction takes several years, hibernation is needed. Near alien planet ship is hitted by meteor or advanced alien stealth rocket. Humans fight with aliens and use generators which slows down time/movements (now I know it was stasis field, inside it fight with melee weapon started, remember Einstein quote about next war after third world war) it makes rifles and lasers useless, instead of it humans use bows and swords, the year is around 3000DC After battle hero backs to Earth (50 or more passed), now it seems that there is peace between aliens and humans Faces of aliens are not shown even one time I think, they are humanoid and in space suits


EDIT: Ok, my question/explanation doesn't seem to be clear enough, so I'll try to restate my goal.  The end result I'm trying to achieve is to hook an empty or bone to each separated face, BUT using the face normal orientation so that the faces can be animated by each hooked empty/bone and the rotation will occur with respect to each face's normal.    I'm trying to find a way to rotate faces of a mesh on their normals. Currently it seems one needs to separate the faces to individual objects in order to control rotation from an empty/modifier/constraint. However once the faces are separated, and Transform>Origin to Geometry is called, the orientation is not based on the original normals of the mesh face.  How does one copy the original normal orientation of the mesh face to the separated object data?  Is there another way to control rotation of mesh faces (assuming the faces have first been separated within the mesh object)?  I should also mention that I'm wondering about a non-scripted solution, as I could probably figure out a script to do it, but was looking for simpler solution first. Feel free to post script solutions though if you want.  Ideally, a solution that allows mesh face rotation on the individual normals based on an external input without separating faces to objects would be preferable.

In edit mode with these settings:   Face selection Pivot point: individual origins Transformation orientation: Normal   The faces don't rotate around the normals, is there another required setting that I overlooked?


I use  addon to create characters and I don't get materials when I import in Unreal Engine 4.13. I am beginner user in Blender and Unreal Engine and I searched the solution how can I export to Unreal Engine that all material will imported in Unreal Engine.  I found that I must use UV things and reproduce colors and after save as png file. But, there is no way to export materials in fbx without change something?  There is no compatible versions? For example blender 2.70 and unreal engine 4.11 or something like that?

I used node textures in a mesh I exported to .FBX.  I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender?


In some movies, you can tell when a character is there only to make a dramatic moment when he/she dies.  Is there a term for a character written specifically to die for dramatic purpose?

I was wondering if there is a title/role in movies, specifically horror or Sci-fi movies, for characters that are cast specifically to die as a way of being an example. This could be as a way to show the cast/party that things have turned horribly wrong or to show what they are up against.   These characters usually die at the beginning of an outbreak or as soon as a there is a troubling encounter with a new obstacle, such as a trap room with a unseen trick.


This semester began to study classical differential geometry, some conceptual things keep confusing me. When I saw Gauss's Egregium theorem, I didn't feel any special place in this theorem. I thought that intrinsic geometry studys invariant properties of a surface completely out of Euclidean space. I've heard that the quantity that is completely determined by the first fundamental form is the intrinsic quantity, but the first fundamental form seems to me to just relate every point on the surface to the surrounding Euclidean space(keep inner product unchanged). That seems not the property of the surface out of Euclidean space, right? In addition, how do we know the first fundamental form of a surface if we don't leave the surface, ultimately all of the studies of surfaces still has to embed surfaces in surrounding space? I know there must be many fallacies in my understanding, please help me correct... thanks!

I'm reading about the differential geometry of surfaces in $\mathbb{R}^3$. I keep seeing statements about certain surface properties being either "intrinsic" or "extrinsic".   Sometimes people say that the intrinsic properties are those that depend only on the coefficients of the first fundamental form. I don't see why you would ever make a definition like this. Why does it matter?  People say that the "intrinsic" properties are related only to the surface itself, whereas extrinsic ones depend on how the surface is "embedded in $\mathbb{R}^3$". I don't understand this at all. What does "embedded in $\mathbb{R}^3$" mean?  If the surface isn't "embedded in $\mathbb{R}^3$", then where is it? Is there more than one way to embed a given surface in $\mathbb{R}^3$?  I see that Gauss was very happy when he managed to prove that Gaussian curvature is an intrinsic property. Gauss was a fairly practical fellow, so I assume that this result has some practical significance. In other words, being "intrinsic" must be a helpful property, somehow. But how?  I work with surfaces in engineering (ship hulls, turbine blades, airfoils, car bodies, etc.) so I like concrete physical explanations better than abstractions. I have read numerous texts on basic differential geometry, so repetition of the standard material probably won't help me much, unless you can throw some new light on it.


Why is the strength of a field (i.e. gravitational or electric) inversely correlated to the square of the radius?  It is clear to me why the further you get a way from a field, the field's enacted force decreases. However, this makes me hypothesize that the relationship should be:  $$F ~=~ k/r$$   However, it is in fact:  $$F ~=~ k/r^2$$  Is this related to the fact that the surface area of a sphere is a function of the square of its radius?   An intuitive explanation would be very much appreciated.

Newton's law of universal gravitation: "Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them."  Coulomb's law: "The magnitude of the Electrostatics force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distances between them."  How did Sir Isaac Newton and Sir Charles Augustine De Coulomb come to know that the force, gravitational or coulomb's,  is inversely proportional to the square of the distance between two point masses or charges, why didn't they just say that the force is inversely proportional to the distance of two bodies from each other or two charges? There must have been something that made them formulate these inverse-square laws.


What does "Auto" setting of white balance do? I know what it is supposed to do but how does it actually work? Does it chose from the various Sunny, cloudy,incandescent white balance settings you have already entered and use one of them?or does it work independently, then applies the adjustment hues you have entered?

I don't understand how the camera can work out the white-balance to use in a given scene.    I could see it working if there is an obvious colour-cast (for example: under fluorescent lights).  Does it compare the histograms from the different colour channels and try to make them match up to some degree? Even then I can only imagine it working reliably in very well-defined circumstances.    Can someone explain how it is implemented in today's cameras, and how well it typically works?


Remove Doubles was removed and replaced with Merge by Distance? If, you set the value small enough it works the same and gives versatility.  Blender 2.8 Beta Version 5/13/19

I'm using 2.8  Is there no default short key combo to remove duplicates now?  I see that I can quickly add a shortcut for it - but it seems to me that it's something that should be in the mesh (w) menu. I use it all the time.  Thanks!


I did 48/2(9+3) as I thought I had been taught and got the incorrect answer of 2. There's got to be a reason why so many are not only getting the wrong answer but consistently getting the same wrong answer. This came up once before when another equation became an internet meme. Math rules didn't change so something else was different for those who get the right answer and those who get 2 for an answer. I suspect it has something to do with when we were taught math and how the problem is presented. I'm 65 and was never taught MDAS. Was it considered unnecessary when I was taught because this problem would have been presented in an alternative fashion to make the mistake unlikely? It would be interesting to do a study of the ages of those who get 2 and those who get 288. I sought an answer to this question back when the last "math problem meme" hit the Net and could not only not get an answer but no one could even understand my question. Hope I have better luck this time.

There is a huge debate on the internet on the value of $48\div2(9+3)$. I believe the answer $2$ as I believe it is part of the bracket operation in BEDMAS.  yields the same answer. I also believe that if $48\div2\times(9+3)$ was asked it would be $288$ which Mathway agrees with as well. However,  says it is $288$ either way. A friend of mine (who is better at math) told me that there is no such thing as 'implicit multiplication', only shorthand so that is in fact done after the division (going left to right, not necessarily because division occurs before multiplication. But he didn't explicitly give a reason) What is the answer and why?


Anyone who's studied thermodynamics knows the fundamental relations for the various free energies: \begin{align} \mathrm{d}U &= T\:\mathrm{d}S- p\:\mathrm{d}V\\ \mathrm{d}F &= -S\:\mathrm{d}T- p\:\mathrm{d}V\\ \mathrm{d}H &= T\:\mathrm{d}S+ V\:\mathrm{d}p\\ \mathrm{d}G &= -S\:\mathrm{d}T+ V\:\mathrm{d}p \end{align} We think of $S,V$ as being the "natural variables" for the energy $U$, and similarly for the other free energies.  But why?  For e.g. an ideal gas, the energy is expressed most easily as a function of $T,V$, where it has the nice form $U=\frac{3}{2} N k T$ (in 3 dimensions, with $N$ particles).  Changing variables to $S,V$ renders it much more complicated.    Of course one "obvious" reason to write the free energies as functions of their natural variables is that then the partial derivatives of the free energies are themselves nice functions (namely, the other state variables).  But is this the only justification?  Or is there some more profound reason to prefer these variables?

I'm struggling with the concept of "natural variables" in thermodynamics. Textbooks say that the internal energy is "naturally" expressed as $$ U = U(S,V,N)$$  For an ideal gas, I could take the  - which gives me $S(U,V,N)$ - and solve for $U$ to get $$U = \frac{3Nh^2}{4 \pi m} \left( \frac{N}{V} \left( \exp \left( \frac{S}{Nk} \right) - \frac{5}{2} \right) \right) ^{2/3} = U(S,V,N)$$  However, I have never seen this expression before. Usually, people invoke the equipartition theorem to get $$U = \frac{3}{2}N k_B T = U(T,N)$$ Or they use the ideal gas law to get $$U = \frac{3}{2}N k_B T = \frac{3}{2}pV = U(p,V)$$  So sticking with the example of the ideal gas, this motivates the following questions:   What is "natural" about $U(S,V,N)$ compared to $U(T,N)$ and $U(p,V)$? Can I derive the expressions for $U(T,N)$ and $U(p,V)$ from $U(S,V,N)$? Can I derive $U(S,V,N)$ from $U(T,N)$ and $U(p,V)$?   Note that this question is not about the Legendre transformation between different thermodynamic potentials but about expressing the same thermodynamic potential $U$ in terms of different variables.


So future-Simon goes back in time and becomes the superhoodie in order to save the gang and to make Alicia fall in love with present-Simon.   But I don't get it. Why on earth would the very first future-Simon travel back in time? Because that Simon didn't have a future-Simon to make Alicia fall in love with him? So Simon would still be kinda shy and not superhoodie, so it does not make sense that he should start the loop.  I know it's a loop with no beginning and end, but still - it's quite unsatisfying to think that "poof" - suddenly you have a future-Simon who already has experienced love with Alicia to start the loop. Please help :)

In episode 6 of the second season, we saw the fulfillment of a number of predictions made earlier in the series.  There are a number of spoilers involved in this question.  Specifically:      We saw the television footage announcing them as the "ASBO Five" being filmed, as well as the interview with Alisha, that we had seen earlier (season 2, episode 3) in Future Simon's apartment as part of the footage and pictures that Future Simon told Alisha was going to occur.  Alisha also reveals to Simon the identity of Future Simon, and their (inevitable?) relationship.   However...      At the end of episode 6, Curtis rewinds time, and they visit "The Big Cheese", at which point we see Curtis punch him.  They then end their community service, implying that none of the events of the rewound timeline ever occur (except in Curtis' memory).     In the Christmas Special, we see the gang several months later.  We find out that:     They are all poor (except, perhaps, Simon, due to the apartment from Future Simon) with mundane jobs.  It seems clear that they never became the "ASBO Five".  However, Alisha and Simon are now dating, and Simon knows about Future Simon.   How does this reconcile?  Does the end of episode 6 create a paradox with the information Alisha sees in episode 3?


I have to calculate this Integral -  $$\int _0^{\frac{\pi }{2}}\:\frac{\sin^{7/2}x}{\sin^{7/2}x+\cos^{7/2}x}dx$$  I have no idea how to start, Hint someone ? Thanks.

Evaluate the integral $$\int^{\frac{\pi}{2}}_0 \frac{\sin^3x}{\sin^3x+\cos^3x}\, \mathrm dx.$$  How can i evaluate this one? Didn't find any clever substitute and integration by parts doesn't lead anywhere (I think).  Any guidelines please?


I use two large LCD displays. I would like to treat one of the displays as two smaller displays.   It would be the opposite of merging two displays to become one continuous desktop space.  For example, when I move one application to one of the smaller virtual display areas and click "Maximize", it would maximize to the size of that virtual display, not to the size of the LCD monitor.

Is there such a thing?  I don't want multiple separate desktops, what I'd like to be able to do is split my main desktop into two areas so that an application in one when maximized won't take up the "Full" physical screen, but its portion of it.  I would like to be able to keep some apps maximized, but still view others off to the side with a single monitor.  Ideas?


I don't see why people care whether someone is muggle-born or not. Does it make any difference? Please illuminate me, I don't understand.

I was checking on something in the Harry Potter wiki and saw Harry listed as "Half-Blood."  Both his parents were magical, but, as we know, his grandparents on his Mother's side were muggles.  This reminds me of the racially loaded terms like octoroon.  (In the south, you still hear those terms every once in a while.)  When there was still segregation, having only 1 great-grandparent of an ethnic group was enough to classify a person of that group.  So how far down the line did it go in the Harry Potter universe?  Just how many generations removed from a muggle-born would a person have to be before they're no longer classified as half-blood or something similar?


I read that a topological space $(X,d)$ is a Baire space if for every sequence $\{X_n\}$ of open dense subsets of $X$, the set $\bigcap_{n=1}^{\infty}X_n$ is also dense in $X$.  Since every complete metrizable space is a Baire space, and since $\mathbb{N}$ is a Polish space (which is complete metrizable by definition), it follows that $\mathbb{N}$ is also a Baire space.  But what if I take $X_n = \mathbb{N} / \{x_n\}$ as a sequence of sets. I think (not sure) that each of these sets is open and dense in $\mathbb{N}$, but we have  $\bigcap_{n=1}^{\infty}X_n=\emptyset$, which is not dense in $\mathbb{N}$.  Or is it that there's something wrong with my understanding that $X_n$ should be dense - given that the only dense subset of a discrete space is the space itself.

Is  the  space $\mathbb{N}$  is a  baire  spaces ?  My attempts :   No ,  It  will not form a  baires  spaces ,  let $C_n= \mathbb{N}\setminus\{n\}$. This is open (since $\{n\}$ is closed in $\mathbb{R}$, hence in the induced topology of $\mathbb{N}$) and dense, since every open ball with center in $\mathbb{n}$ intersects ${C_n}$. But  $$\bigcap_{n\in\mathbb{N}} {C}_n = \emptyset$$  So $\mathbb{N}$ is not a baires  spaces because for  Baire Space the intersection of a countable family of open dense sets must be dense.   Is  Its correct or not ?


How do I make it so when my webpage is viewed on mobile, the container is centered in the middle. Like at 545x600, it looks centered but at 575x600 it slightly off.   @media only screen and (max-width: 600px) {   .a2c {      margin: 0px 0px 80px 115px !important;      width: 350px !important;     height: 380px !important;   }    .img1 {     width: 100% !important;     height: 75% !important;   }    .bgimg-1 {     height: 75% !important;   }     .titletext {     font-size: 15px !important;   }    .text {     font-size: 12px !important;     margin-top: 5px !important;   } }

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How can I horizontally center a
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I ran into another problem with JS created inputs. I want the input to focus on the next one as soon, as it gets filled. So I write a number -> boom I'm on another input. I found this code, already posted on StackOverflow:  var inputs = $(':input').keypress(function(e){      if (e.which == 13) {        e.preventDefault();        var nextInput = inputs.get(inputs.index(this) + 1);        if (nextInput) {           nextInput.focus();        }     } });   Which I edited to:  var inputs = $(':input').keypress(function(e){     var nextInput = inputs.get(inputs.index(this) + 1);    if (nextInput) {       nextInput.focus();    } });   It works fine. Until I ad new inputs with JS createElement() function. Then it always stops on the last input that was on the page right after load.  Any solutions? You can follow my work .  Thanks!

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


There is a question 6.20 from the Book of Proof by Hammock that reads as follows:  We say that a point $P=(x,y) \in R^2$ is rational if both x and y are rational. More precisely, P is rational if $P=(x,y) \in Q^2$.  An equation $F(x,y)=0$ is said to have a rational pointif there exists $x_0, y_0 \in Q$ such that $F(x_0,y_0)= 0$.  For example, the cruve $x^2+y^2-1=0$ has rational point $(x_0,y_0)=(1,0)$.  Show that the curve $x^2+y^2-3=0$ has no rational points. I can only take a guess at how to start a proof.  Doing algebra on both sides of $x^2+y^2-3=0$ yields $y = \sqrt{3-x^2}$.  Now, assume y is rational -- can x be rational? Thus, let y = $a\over b$ for some integers a and b, $b \ne  0$,$gcd(a,b)=1$.  Then let y = $c\over d$ for some integers c and d, $d \ne  0$,$gcd(c,d)=1$.  Hence, ${a \over b} = \sqrt{3 - {{c^2} \over {d^2}}}$. I think I may want to prove some sort of contradiction in terms of rational and irrational?  This as far as I got in my scratchwork for a proof.

Show that the curve $x^2+y^2-3=0$ has no rational points, that is, no points $(x,y)$ with $x,y\in \mathbb{Q}$.   Update: Thanks for all the input! I've done my best to incorporate your suggestions and write up the proof. My explanation of why $\gcd(a,b,q)=1$ is a bit verbose, but I couldn't figure out how to put it more concisely with clear notation.  Proof: Suppose for the sake of contradiction that there exists a point $P=(x,y)$, such that $x^2+y^2-3=0$, with $x,y\in\mathbb{Q}$. Then we can express $x$ and $y$ as irreducible fractions and write $(\frac{n_x}{d_x})^2+(\frac{n_y}{d_y})^2-3=0$, with $n_x, d_x, n_y, d_y\in\mathbb{Z}$, and $\gcd(n_x,d_x)=\gcd(n_y,d_y)=1$.  Let $q$ equal the lowest common multiple of $d_x$ and $d_y$. So $q=d_xc_x$ and $q=d_yc_y$ for the mutually prime integers $c_x$ and $c_y$ (if they weren't mutually prime, then $q$ wouldn't be the lowest common multiple). If we set $a=n_xc_x$ and $b=n_yc_y$, we can write the original equation as $(a/q)^2+(b/q^2)-3=0$, and equivalently, $a^2+b^2=3q^2$.  In order to determine the greatest common divisor shared by $a$, $b$, and $q$, we first consider the prime factors of $a$. Since $a=n_xc_x$, we can group them into the factors of $n_x$ and those of $c_x$. Similarly, $b$'s prime factors can be separated into those of $n_y$ and those of $c_y$. We know that $c_x$ and $c_y$ don't share any factors, as they're mutually prime, so any shared factor of $a$ and $b$ must be a factor of $n_x$ and $n_y$.  Furthermore, $q=d_xc_x=d_yc_y$, so it's prime factors can either be grouped  into those of $d_x$ and those of $c_x$, or those of $d_y$ and those of $c_y$. As we've already eliminated $c_x$ and $c_y$ as sources of shared factors, we know that any shared factor of $a$, $b$, and $q$ must be a factor of $n_x$, $n_y$, and either $d_x$ or $d_y$. But since $n_x/d_x$ is an irreducible fraction, $n_x$ and $d_x$ share no prime factors. Similarly, $n_y$ and $d_y$ share no prime factors. Thus $a$, $b$, and $q$ share no prime factors, and their greatest common divisor must be $1$.  Now consider an integer $m$ such that $3\nmid m$. Then, either $m\equiv 1\pmod{3}$, or $m\equiv 2\pmod{3}$. If $m\equiv 1\pmod{3}$, then $m=3k+1$ for some integer $k$, and $m^2=9k^2+6k+1=3(3k^2+2k)+1\equiv 1\pmod{3}$. Similarly, if $m\equiv 2\pmod{3}$, then $m^2=3(3k^2+4k+1)+1\equiv 1\pmod{3}$. Since that exhausts all cases, we see that $3\nmid m \implies m^2\equiv 1\pmod{3}$ for $m\in\mathbb{Z}$.  Notice that $a^2+b^2=3q^2$ implies that $3\mid (a^2+b^2)$. If $3$ doesn't divide both of $a$ and $b$, then $(a^2+b^2)$ will be either $1\pmod{3}$ or $2\pmod{3}$, and thus not divisible by $3$. So we can deduce that both $a$ and $b$ must be divisible by $3$.  We can therefore write $a=3u$ $\land$ $b=3v$ for some integers $u$ and $v$. Thus, $9u^2+9v^2=3q^2$, and equivalently, $3(u^2+v^2)=q^2$. So $3$ divides $q^2$, and must therefore divide $q$ as well. Thus, $3$ is a factor of $a,b,$ and $q$, but this contradicts the fact that $\gcd(a,b,q)=1$, and falsifies our supposition that such a point $P=(x,y)$ exists.


From the formula $\sin(\frac{\pi}{2}-x)=\cos x$, find a formula relating $\arcsin (x)$ and $\arccos (x)$.  I have no idea where to start.

From the formula $\sin\left(\frac{π}{2}−x\right)=\cos x$, find a formula relating $\operatorname{arcsin}(x)$ and $\operatorname{arccos}(x)$.   I have figured out that the domain of $x$ is $[-1;1]$, but I have no idea how to do this. I've tried letting $y=\cos x$ and the only result I've got is $$\operatorname{arccos}(y)+\operatorname{arcsin}(y)=\frac{π}{2}$$ I need a full answer.


What are reasons my UV map doesn't show up in 3D view?    3D view in object and edit mode only shows a wireframe.   However when I render, I can see the UV map applied.

I'm new to Blender and this site, so I apologize in advance if I'm not following any of the proper etiquette.  I'm no artist, but I'm trying to learn Blender so that I have some programmer art for me to work around in Unity.    I followed a tutorial for making a basic human model, I rigged it with rigify, and now I'm starting to export it following yet another tutorial.  The thing is, when I was trying to rig the model, I couldn't get the model to go transparent so that I could see the bones inside the model.  Eventually, I managed to get it into wireframe mode, but I can't get it back into solid mode.    It's probably just a display thing and not a property of the model itself, but I want to be sure.  I'm looking at the display options under the "Figure" pane in Blender, and none of the Display check boxes are checked, including the one that says "Wire".  I don't want to import a plain wireframe model into Unity, and even if that doesn't happen, this is functionality of Blender that I should really know anyway, so I'd appreciate any help that anyone has to offer.  If necessary, I can upload the .blend file, but I'm not sure what site people would prefer that I upload it to.


I have an array like this:  message_list = [     {         "Main_body": "test msg",         "emp_name": "test",         "emp_salary": "5000 USD"     } ]   Its length (e.g., message_list.length) is 1.  Now I have another array like this:   added_user_data = [     {         "PostSharedLog": {             userids: "2,4,5"         },         "created": "2123123"     },      {         "PostSharedLog": {             userids: "3,1"         },         "created": "2123147"     } ]   Its length (added_user_data.length) is 2.  I want to push the above array added_user_data into message_list.   I tried doing it inside a for loop, now since the length of message_list is 1, for the second iteration, the values do not get pushed since message_list[1] does not exist and is undefined. But I still want to create message_list[1] even if it does not exist.  if i do the below :   for(var k =0;<count(added_user_data.length);k++) {       message_list[k].PostSharedLog = added_user_data[k].PostSharedLog ;  }   It only appends the first row from the array added_user_data  and gives an output like this when i print out message_list :  [{          "Main_body": "test msg",         "emp_name": "test",         "emp_salary": "5000 USD",          "PostSharedLog": {             userids: "2,4,5"         } }]   The second iteration does not append anything at all .   I would like to see the below :   [{              "Main_body": "test msg",             "emp_name": "test",             "emp_salary": "5000 USD",              "PostSharedLog": {                 userids: "2,4,5"             },             "PostSharedLog": {                 userids: "3,1"             }    }]

How do I append an object (such as a string or number) to an array in JavaScript?


I am not a mathematician at all and I had a thought about Pi that I can't work out.  Pi is irrational, with an infinite sequence of numbers A recurring number is infinite  Would it be theoretically possible that at one point down Pi's sequence, it just turned into an infinite sequence of one number?  If not, what is stopping this?  I recognise through reductio ad absurdum that my proposition is impossible, as it means that PI must at some point end in all of 1-recurring and 2-rcurring...9-recurring simultaneously, but I lack the toolset to understand where my thinking breaks down.

We know $\frac{1}{81}$ gives us $0.\overline{0123456790}$  How do we create a recurrent decimal with the property of repeating:  $0.\overline{0123456789}$  a) Is there a method to construct such a number?  b) Is there a solution?  c) Is the solution in $\mathbb{Q}$?  According with this Wikipedia page:  One could get this number by applying this series. Supppose:  $M=123456789$, $x=10^{10}$, then $0.\overline{0123456789}= \frac{M}{x}\cdot$ $\sum$ ${(10^{-9})}^k$ $=\frac{M}{x}\cdot\frac{1}{1-10^{-9}}$ $=\frac{M}{9999999990}$  Unless my calculator is crazy, this is giving me $0.012345679$, not the expected number. Although the example of wikipedia works fine with $0.\overline{123}$.  Some help I got from mathoverflow site was that the equation is: $\frac{M}{1-10^{-10}}$. Well, that does not work either.  So, just to get rid of the gnome calculator rounding problem, running a simple program written in C with very large precision (long double) I get this result:  #include <stdio.h>  int main(void) {   long double b;   b=123456789.0/9999999990.0;   printf("%.40Lf\n", b);  }   Result: $0.0123456789123456787266031042804570461158$  Maybe it is still a matter of rounding problem, but I doubt that...  Please someone?  Thanks!  Beco  Edited:  Thanks for the answers. After understanding the problem I realize that long double is not sufficient. (float is 7 digits:32 bits, double is 15 digits:64 bits and long double is 19 digits:80 bits - although the compiler align the memory to 128 bits)  Using the wrong program above I should get $0.0\overline{123456789}$ instead of $0.\overline{0123456789}$. Using the denominator as $9999999999$ I must get the correct answer. So I tried to teach my computer how to divide:  #include <stdio.h> int main(void) {     int i;     long int n, d, q, r;     n=123456789;     d=9999999999;     printf("0,");     n*=10;     while(i<100)     {         if(n<d)         {             n*=10;             printf("0");             i++;             continue;         }         q=n/d;         r=n%d;         printf("%ld", q);         if(!r)             break;         n=n-q*d;         n*=10;         i++;     }     printf("\n"); }


Suppose $k$ and $n$ are integers such that $1\leq k<n$ and $\gcd(n,k)=1$. Why is it that $\gcd(n-k,n)=1$ as well?   $\gcd(n,k)=1$ implies that there exist integers $a,b$ such that $an+bk=1$, but I can't see if/how this will end up being useful.

Given: $a = qb + r$. Then it holds that $\gcd(a,b)=\gcd(b,r)$. That doesn't sound logical to me. Why is this so?    Addendum by LePressentiment on 11/29/2013: (in the interest of  and averting a duplicate)  What's the intuition behind this result? I only recognise the proof and examples solely due to algebraic properties and formal definitions; I'd like to apprehend the result naturally.


At least for successful beta sites, the new design seems to result in a lack of whitespace between the numbers and what the numbers represent.  Because a picture is worth a thousand words, even though this particular example comes straight off the presses at :

This is now out for all of the sites  We've had the new default unified theme up on  for a month and a half now and the response there has been really positive. We got a lot of great feedback from the PPCG community and worked out a lot of trouble spots.   If you've been following the progress on my , you'll know that one of the staff will usually post a discussion on each meta site as the theme rolls out. With so many sites using this theme, we decided it'd be easier to post one announcement here on MSE and feature it so that the entire network can see it and respond in one place, as a bug on one site will probably be affecting all of them.  We don't expect there to be any bugs in this theme (famous last words, apparently), since it's been used for a while on PPCG but if you do see anything amiss, please use this post to point it out so that we can dig into it. Some of your concerns may already be mentioned on the PPCG announcement post I linked at the beginning of this one, so please check there to see if they've been reported yet.  If you have general concerns about left navigation or responsive design, please use the .  Some things to be aware of:   Left Navigation is active on most pages (but can be collapsed into a menu by visiting your site preferences - ). Responsive layout is active, which lets the site adjust as browser widths change - no side scrolling (some pages haven't been updated, yet, though). For now, if you prefer the scrolling, you can disable this by clicking the "disable responsiveness" link in the footer. Link underlining is active. In an effort to make links more visible, they are now being underlined.     While this change is definitely something many users have strong feelings about, I'm really excited about this step in particular because it means that some very long-standing communities will be a lot closer to getting custom themes. We have about ten sites that are no longer in beta but haven't gotten a custom design yet, and once this changeover is complete, we'll move forward in designing those sites - and maybe others.  The layout unification is also allowing us to more easily improve existing features like  and develop new features that have long been requested like , which is currently in testing. We'd love to get more features out to you all and that's easier when we spend more time working on the new features and less time squashing bugs they cause because we have 60+ very different site layouts.  This is addressed in a  if you want more detail.    I'll be doing my best to keep an eye out for - and respond to - questions asking about this change on the child metas for all of the beta sites as we transition to the responsive design but feel free to link users here as well.


I am experiencing situational depression. This isn't 'discouragement' due to research. Me feeling inadequate in my research is NOT the problem. The problem is that the steps involved in research seem to be at best, not helping, or worse - exacerbating the negative emotions that are associated with depression.  Let me rephrase that - I have not felt 'impostor syndrome', and I do not feel it now (sorry if it sounds a tad bigheaded but I want to avoid confusion).  I have some idea of the things I need to do to combat depression, but it seems to me that they all involve staying away from work at the lab. Has anyone faced this? Can I do anything to prevent loss of productivity?  Usually, I hear the following ways to fight depression:   Get in a routine. Set goals. Do something new (don't get stuck in a rut)   Now, these can be applied when I am free. But the majority of my waking hours are in the lab (or supposed to be). While doing bio research:   The routine/ schedule is thrown off whack by unforeseen developments/ etc.  Goals, even minor ones, may or may not be reached. This is research. Can't help getting stuck in a rut if we're trying to get data out of a particular experiment.    I took a week off, and it helped, but doesn't seem to have helped enough. Any suggestions?

I am a third year (starting fourth year in the fall) PhD student in mathematics. I've passed all qualifying exams and am currently doing research. As far as I can tell, I am not doing poorly. I have the good fortune of having a great advisor, being in a very supportive department, and having friends and family who genuinely care about my success.   The fact is research is hard. It appears to consist primarily of staring at a problem for days and days and days without getting anywhere. Sometimes, rarely, I do figure something out and that feels wonderful, but the overwhelming majority of my time appears to be spent banging my head against a mostly figurative wall. I am not complaining about the material being hard, and I am not averse to putting in hard work, but I get frequently discouraged when I realize the vast volumes of mathematics that I yet know nothing about (and probably never will). It's very hard to quantify progress - in particular, there are too few tangible returns after too many hours worked. I find myself thinking along the lines of "Oh, if only someone actually smart were thinking about this problem they would have solved it in moments" and so on.   I've talked about this to some number of people; here is some advice I have received:   Take a day off. Putting in hours upon hours of trying things doesn't magically lead to a solution, particularly if the brain is tired and just wants to sleep. Have a hobby. Since math research doesn't exactly provide instant gratification, a hobby might provide some instead.  Talk to other graduate students. Realize that many graduate students go through this.   I'm interested to know how other folks have dealt with being discouraged as a graduate student. Does it get better with time and experience? Is this a sign that research is not for me and that I should seriously consider a life outside academia?


I generate a mysql query via $_GET in PHP via concatenation assignment (.=). take a look:  $sql='SELECT * FROM table WHERE '; $sql.='ID='.$_GET['id'].''; $query=$PDO->prepare($sql);   how can i prevent mysql injection? i use bind values for direct queries but in this case,i don't have any idea how i should write my code to be safe enough. note that i use PHP 7 and i can't use mysql_real_escape_string(); as it's not available in PHP7.

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


is my 3nd favorite web after  and , everyday i always watch new video from Youtube, but I do not like about YouTube is video buffering,  so annoying to wait it. Now my question is there ways/program to install YouTube Videos quickly and user friendly ?  UPDATE  I know there's many ways to download YouTube videos using terminal, add-ons and other but any is there anyone here who can explain it in detail and use simple words ?

What are instructions on how to download videos from YouTube?    Notice: Terms of Service Violation  Please be aware that by following any of the answers below, you will be violating YouTube's . In particular, from Section 5.B.:     Content is provided to you AS IS. You may access Content for your information and personal use solely as intended through the provided functionality of the Service and as permitted under these Terms of Service. You shall not download any Content unless you see a “download” or similar link displayed by YouTube on the Service for that Content. You shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content. YouTube and its licensors reserve all rights not expressly granted in and to the Service and the Content.


Let $(a_n)_{n\geq 1}$, be a sequence of real numbers satisfying $|a_n|\leq 1$ for all $n$.   let $A_n = \frac{1}{n}(a_1 + a_2 + \cdots + a_n)$, for $n\geq 1$. Then find  $$\lim_{n \rightarrow \infty}\sqrt{n}(A_{n+1} − A_n)$$.    My attempt:  $\lim_{n \rightarrow \infty}\sqrt{n}(A_{n+1} − A_n)$  =$\lim_{n \rightarrow \infty}\sqrt{n}[$$\frac{1}{n+1}(a_1 + a_2 + \cdots + a_n+a_{n+1})-$$\frac{1}{n}(a_1 + a_2 + \cdots + a_{n}$)]  =$\lim \frac{na_{n+1}-a_n}{\sqrt{n}(n+1)} $  I need suggestion here. thanks

Let $\{a_n\}, {n\geq 1}$, be a sequence of real numbers satisfying $|a_n|\leq 1$ for all $n$. Define  $$A_n = \frac{1}{n}(a_1 + a_2 + \cdots + a_n),$$ for $n\geq 1$. Then find $\displaystyle\lim_{n \rightarrow \infty}\sqrt{n}(A_{n+1} − A_n)$ .    I proceed in this way  $$\lim_{n \rightarrow \infty}\sqrt{n}(A_{n+1} − A_n)=\lim_{n \rightarrow \infty}\sqrt{n}\left[\frac{1}{n+1}(a_1 + a_2 + \cdots + a_n+a_{n+1})-\frac{1}{n}(a_1 + a_2 + \cdots + a_{n})\right]=\lim_{n \rightarrow \infty}\left[{(na_{n+1}-a_1 - a_2 - \cdots - a_n})\frac{1}{\sqrt{n}(n+1)}\right]$$  Please help me to complete from here


How does a[i] and i[a] give the same result in C?   |i| is not an array, so i[a] should be syntactically incorrect, but gives the same output as a[i].   I have tested the code at .  Please explain.  Thanks.

As Joel points out in , in  (aka: K & R), there is mention of this property of arrays in C: a[5] == 5[a]  Joel says that it's because of pointer arithmetic but I still don't understand. Why does a[5] == 5[a]?