If $x + \sqrt{x + \sqrt{x + \cdots}} = 2$, what is the value of $x$?
$$\sqrt{x + \sqrt{x + \sqrt{x + \cdots}}}= 5$$
I don't need a recommendation or a list but my knowledge of GPS and "navi"s and the differences between them is an utter mystery to me.  But often I'm lost in backstreets in random countries where access to something like a live Google Maps would be awesome. I absolutely cannot afford a smartphone with worldwide roaming though.  Can GPS's do what I want or am I barking up the wrong tree? If they can is it only high end ones than can? How not to show Universal Access menu Icon in task bar in Ubuntu 18.04? Is it standard for graduate students to get gifts for their advisors? Is it standard for graduate students to give their advisors gifts around Christmas, like chocolates or bottles of wine?  What about other important people, such as their thesis committee members, or department secretaries? Entering U.S. exactly on the day of visa "expiration date" Let $f$ be a continuous function on a set $E$.  Is it always true that $f^{-1}(A)$ is always measurable if $A$ is measurable?  I say no.  We know that $\bar{\psi(x)}:=\frac{\phi(x)+x}{2}$ where $\phi$ is the Cantor (or Cantor-Lebesgue) function and $\bar{\psi}:[0,1] \rightarrow [0,1]$.  We know this function maps a measurable subset of $C$ (the Cantor set) into a non-measurable set $W$.  A few observations about $\bar{\psi(x)}$.  It is strictly increasing and continuous, so it has a continuous inverse $\bar{\psi(x)}^{-1}$.  Thus $\bar{\psi(x)}^{-1}(W)=c \subset C$; that is, $\bar{\psi(x)}^{-1}(W)$ is non-measurable, but c is.  Is this correct? can't type lower cased e in amazon ec2 (Amazon Linux) After a few days of operation on my new ec2 build, the following happens:   I log into SSH, everything is fine, I do my coding I return the next day, and log into SSH I cannot type a lower cased e anymore--I get the error ding when I type it I try to ssh from a different computer, same problem I reboot the server, same problem I open nano or vi and e works fine, just not in bash or sh I terminate the server, create a new one, install from scratch, a few days later it happens again   This is baffling! Where do I even start to troubleshoot?  My Local Machine Setup(s):   windows XP or 7 putty (latest) or cygwin/openssh   The EC2 setup   Amazon Linux (default options) node.js iptables forwarding port 80 to node on port 8003 emacs, npm, and openssl-devel no other mods       Output of stty -a while I can't type an e  sh-4.1$ stty -a speed 38400 baud; rows 30; columns 95; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = &lt;undef&gt;; eol2 = &lt;undef&gt;; swtch = &lt;undef&gt;; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0; -parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts -cdtrdsr -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8 opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0 isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke   In case it helps someone else with a similar issue, I created a script (called sub) to convert upper-cased E to lower-cased, then echo the command back. Then I run it in backticks to get an e on the command line::  #!/bin/sh echo ${@//E/e}  &gt; `sub Emacs /Etc/profilE`   UPDATES   This breaks for all users In bash only (csh works fine) In emacs edit mode only   I've created  and hone in the solution. Can't upgrade due to low disk space on /boot I try to do do-release-upgrade but then I get:       Not enough free disk space      The upgrade has aborted. The upgrade needs a total of 25.7 M free   space on disk '/boot'. Please free at least an additional 25.7 M of   disk space on '/boot'. Empty your trash and remove temporary packages   of former installations using 'sudo apt-get clean'.   Output of df:                      237251272 214797108  10402504  96% / udev                    488120         4    488116   1% /dev tmpfs                   198676       668    198008   1% /run none                      5120         0      5120   0% /run/lock none                    496684         0    496684   0% /run/shm /dev/sda1               233191    225867         0 100% /boot   How come there is no space left on boot? Here's the output of ls -as /boot:  total 221839     4 .     4 ..   645 abi-2.6.32-34-generic-pae   698 abi-2.6.35-30-generic-pae   727 abi-2.6.38-12-generic-pae   727 abi-3.0.0-12-generic-pae   727 abi-3.0.0-13-generic-pae   727 abi-3.0.0-14-generic-pae   727 abi-3.0.0-15-generic-pae   727 abi-3.0.0-16-generic-pae   727 abi-3.0.0-17-generic-pae   727 abi-3.0.0-19-generic-pae   761 abi-3.0.0-20-generic-pae   115 config-2.6.32-34-generic-pae   128 config-2.6.35-30-generic-pae   136 config-2.6.38-12-generic-pae   140 config-3.0.0-12-generic-pae   140 config-3.0.0-13-generic-pae   140 config-3.0.0-14-generic-pae   140 config-3.0.0-15-generic-pae   140 config-3.0.0-16-generic-pae   140 config-3.0.0-17-generic-pae   140 config-3.0.0-19-generic-pae   140 config-3.0.0-20-generic-pae     5 grub 10773 initrd.img-2.6.32-34-generic-pae 13619 initrd.img-2.6.35-30-generic-pae 15365 initrd.img-2.6.38-12-generic-pae 16481 initrd.img-3.0.0-12-generic-pae 16487 initrd.img-3.0.0-13-generic-pae 16501 initrd.img-3.0.0-14-generic-pae 16476 initrd.img-3.0.0-15-generic-pae 16481 initrd.img-3.0.0-16-generic-pae 16478 initrd.img-3.0.0-17-generic-pae    12 lost+found   174 memtest86+.bin   176 memtest86+_multiboot.bin  1700 System.map-2.6.32-34-generic-pae  1841 System.map-2.6.35-30-generic-pae  2115 System.map-2.6.38-12-generic-pae  2141 System.map-3.0.0-12-generic-pae  2141 System.map-3.0.0-13-generic-pae  2143 System.map-3.0.0-14-generic-pae  2146 System.map-3.0.0-15-generic-pae  2147 System.map-3.0.0-16-generic-pae  2147 System.map-3.0.0-17-generic-pae  2148 System.map-3.0.0-19-generic-pae  2149 System.map-3.0.0-20-generic-pae     2 vmcoreinfo-2.6.32-34-generic-pae     2 vmcoreinfo-2.6.35-30-generic-pae     2 vmcoreinfo-2.6.38-12-generic-pae     2 vmcoreinfo-3.0.0-12-generic-pae     2 vmcoreinfo-3.0.0-13-generic-pae     2 vmcoreinfo-3.0.0-14-generic-pae     2 vmcoreinfo-3.0.0-15-generic-pae     2 vmcoreinfo-3.0.0-16-generic-pae     2 vmcoreinfo-3.0.0-17-generic-pae     2 vmcoreinfo-3.0.0-19-generic-pae     2 vmcoreinfo-3.0.0-20-generic-pae  4092 vmlinuz-2.6.32-34-generic-pae  4347 vmlinuz-2.6.35-30-generic-pae  4567 vmlinuz-2.6.38-12-generic-pae  4675 vmlinuz-3.0.0-12-generic-pae  4676 vmlinuz-3.0.0-13-generic-pae  4681 vmlinuz-3.0.0-14-generic-pae  4698 vmlinuz-3.0.0-15-generic-pae  4700 vmlinuz-3.0.0-16-generic-pae  4700 vmlinuz-3.0.0-17-generic-pae  4703 vmlinuz-3.0.0-19-generic-pae  4705 vmlinuz-3.0.0-20-generic-pae   Output of uname -a:   Linux kitsch 3.0.0-17-generic-pae #30-Ubuntu SMP Thu Mar 8 17:53:35 UTC 2012 i686 i686 i386 GNU/Linux How to avoid messages from applications which I ran with a &? I ran dolphin like this:  dolphin . &amp;   I see messages in the console like these:  QPixmap::scaled: Pixmap is a null pixmap   How can I keep the console clean or silent? Can I find out which tags I have created? This would be interesting to know.  The tags could be highlighted on the users page for example. I am trying to find out how to approach a relief type project. I have a background image and a flat plane mesh to sculpt on, but I actually don´t see any changes looking straight on top. When I tilt the perspective a bit the image disappears.  Is there a way to make the image appear at all perspectives? Self-explanatory title really! A student today asked me why they were called integral domains -- and I realised that the word "integral" seems to be being used in a way totally unlike any other way I hear it used in mathematics. The student suggested that "integral" was used because the integers were an example -- but I didn't buy this because by that logic they could have been called "rational domains" or "real domains".  Any ideas anyone? Can cited works hold grammatical positions in sentences? Though I read this style quite often, I was recently told unambiguously by a reviewer that I was NOT supposed to use citations "as if they are objects in a sentence."  The following sentence is an example of what the reviewer considered unacceptable:       We analyzed the data using the Wilmerding method, guided by [12].   The references section might include the following:      [12] Smith, D., Marshawn, J., &amp; Devenshaw, A. 2011. Techniques and   Procedures for Applying the Wilmerding Method.  Prince Publications,   Inc, New York, NY.   The Wilmerding method1 is not a step-by-step algorithm that can be precisely followed as if by a machine, and thus [12] does not provide a step-by-step algorithmic description but rather guidance for using  the method. [12] is a relatively slim but authoritative textbook about how to use the Wilmerding method.  Within this question, for the purpose of discussion, I have intentionally put [12] in grammatical positions where it's an important element of the sentence and the sentence would make less sense without the reference.  Sometimes that seems to be the most efficient way to communicate the intended message.  Is using a reference as a grammatical sentence element like this OK?   Why might this not be considered acceptable?   Should I be rewording those sentences?  Is it enough of a violation to be worth passing the note on to authors of papers I review?   I considered posting this on  but it seems more specific to academia than general English usage, and the comment came from a content reviewer rather than a copy editor.   is related but it seems to be more about when to put authors names' in vs. outside of the parentheses in an APA-like style.   The numbered citation style (as opposed to following APA, for example) is required by the venue.  1: Fictionalized for the purpose of this discussion How to dump a man page? short view distance in 3d view? Listings - Only highlight between delimiters I want to implement a function name color highlighting and I use the listings package. My 'regex' for this is def %s( where def (including space) is the first delimiter %s is the function name and ( is the second delimtier. Now my aim is to color only %s in purple. So basically I want to only touch the part between the delimiters and the delimiters should stay untouched.  Here is what I tried so far:  \documentclass{article} \usepackage{xcolor,listings} \usepackage[ngerman]{babel} \usepackage{fontspec} \setmonofont{Courier New}  \begin{document}  \lstset{language=Python,     escapebegin=\color{orange},     keywordstyle=\color{blue}\bfseries,     commentstyle=\color{orange!80!red},     stringstyle=\ttfamily\color{gray},     %moredelim = [is][\color{blue}\bfseries def \mdseries\color{purple}]{def\ }{(},     moredelim = [s][\color{purple}]{def\ }{(},     showstringspaces=false}‎ \lstset{literate=%    *{0}{{{\color{red}0}}}1     {1}{{{\color{red}1}}}1     {2}{{{\color{red}2}}}1     {3}{{{\color{red}3}}}1     {4}{{{\color{red}4}}}1     {5}{{{\color{red}5}}}1     {6}{{{\color{red}6}}}1     {7}{{{\color{red}7}}}1     {8}{{{\color{red}8}}}1     {9}{{{\color{red}9}}}1 }  ‎‎\begin{lstlisting}[basicstyle=\ttfamily,mathescape] def fancy_function_name(page_url = 'tex.stackexchange.com'):     return page_url.split('.')[0] \end{lstlisting}  \end{document}   This code will generate:   You can see that it matches the right place but is too greedy and colors the delimiters too. So I thought about the uncommented line: %moredelim = [is][\color{blue}\bfseries def \mdseries\color{purple}]{def\ }{(}, If I use this one and uncomment the line below I get this result:    It's nearly what I wan't but I cannot add the last, now missing ( in black color.  Does anyone has a solution for this without pretouching the code and add all the @@ symbols? Opening Ubuntu 20.04 Desktop on WSL2 I installed Ubuntu 20.04 (server/terminal) from the Windows 10 app store, and then after launching the Ubuntu Terminal via WSL2 (Windows Subsystems for Linux) , I installed Ubuntu Desktop and did several steps to try and get a desktop instance of Ubuntu 20.04 launched.  In short, the steps involved editing the .bashrc file, installing Xming, and then attempting to open the Ubuntu desktop in Xming with the &quot;startxfce4&quot; command.  However, &quot;startxfce4&quot; just doesn't open the desktop for me.  I can get programs to open with &quot;grun&quot; and the file explorer to open with &quot;gopen&quot; though, so it is working partially. Does anyone have any alternative suggestions to how I might get the terminal to open up the full Ubuntu Desktop?  Obviously, this wasn't what Windows had in mind with WSL2 so this is kind of a reach, but any input would be helpful.  Could I somehow do this from the file explorer or with a program that could opened from &quot;grun&quot; or &quot;gopen&quot;? In the TV show Quantum Leap Sam Beckett would travel history and "right" wrongs, temporarily displacing someone native to that timeline in the process. Would the memories of what Sam did transfer to the person he displaced upon his leaping out, or would they wind up with amnesia for the time Sam was there? I wrote a bash script as below:  #!/bin/bash echo "Enter a file name" read filename import -window root $HOME/Desktop/$filename.png   I expected this script to take a screen shot and save the image with the given filename on my desktop.  Problem:  My Ubuntu terminal is giving error:     import: Command Not Found $\frac{1}{99989999} = 1.00010002000300050008001300210034005500890144... \times 10^{-8}$    (), which includes the Fibonacci sequence $(1\ 1\ 2\ 3\ 5\ 8\ 13\ 21\ 55\ 89\ 144\ldots )$.  This is fascinating to me but I can't figure out how this works, and a Google search doesn't seem to reveal anything. I see stuff like command 1&gt; out or with 2&gt;&amp;1 to redirect stderr, but sometimes I also see &amp;&gt; by itself, etc.  What is the best way to understand &amp; and what it means exactly?