Well we know about quadratic equations, but quad means four, but quadratic equations have two roots. So why is it so?
The word "quad" generally means 4. Quadratics don't have 4 of anything. Can anyone explain where the name comes from?
When did you wake up?      I woke up at 10.   But then if I say, “When did you sleep?”     I slept at 10. – seems difficult to digest!   That's because sleep is a process that includes duration.     I slept for 10 hours. – this way, it's digestible!   But when I mention the point of time, is it okay?   Strange thing is, if I'm describing my habit/routine, it's perfectly fine..     I sleep at/by 10     I request not to take this question 'logically'. It's about English. Nobody is perfect in timing. Please don't argue that you cannot have 'perfect time' of sleeping because you don't know when you slept. I'm talking about the sentence structure and not precise timings.   By the way, “I slept at 10” is very common in India. This question is about finding reasons for compile errors when using tikz.  Consider the files compiles.tex, compiles-not1.tex and compiles-not2.tex. Then it is clear that compiles-not1.tex does not compile, because the name C has not been assigned. The file compiles-not2.tex does not compile, because \draw (A) -- (A -| B ); contains a space after the name B. However, this is difficult to see from the error message.   Is it possible to tweak the error messages generated by tikz to perhaps mark tikz-code and names in some way? What I mean is that in the example, an error message ! Package pgf Error: No shape named 'B ' is known. might be more helpful, as the space in the name B\␣ (B with a trailing space) is more clearly delimited from the message.   File compiles.tex compiles without errors.  \documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture}     \node (A) {A};     \node[above right of=A] (B) {B};     \draw (A) -- (A -| B); \end{tikzpicture} \end{document}   On compilation compiles-not1.tex generates ! Package pgf Error: No shape named C is known.  \documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture}     \node (A) {A};     \node[above right of=A] (B) {B};     \draw (A) -- (A -| C); \end{tikzpicture} \end{document}   compiles-not2.tex generates ! Package pgf Error: No shape named B  is known.  \documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture}     \node (A) {A};     \node[above right of=A] (B) {B};     \draw (A) -- (A -| B ); \end{tikzpicture} \end{document} How to draw density estimate on histogram by pgfplots? I know how to draw a density histogram using pgfplots from this answer: .  But how can I draw an estimate line on the histogram like this?    \documentclass{article} \usepackage{pgfplots} \begin{document} \pgfplotsset{     small,     every axis plot post/.style={         fill=orange!75,         draw=orange!50!black     },     trim axis left }  \begin{tikzpicture} \begin{axis}[ymin=0, title=\texttt{hist=density}] \addplot [hist=density] table [y index=0] {random.txt}; \end{axis} \end{tikzpicture} \end{document} JavaScript window resize event Django: AppRegistryNotReady() Ralink MT7601U (148f:7601) Wi-Fi adapter installation I am trying to install a Ralink wifi adapter in Ubuntu Desktop 14.04.  The system is not detecting the wifi.   lsusb lists the device as:  Bus 002 Device 004: ID 148f:7601 Ralink Technology, Corp.  I have the rt2800 USB driver listed in "/etc/modules"; Following some instructions on the web, I tried this command:  echo 148F 7601 | sudo tee /sys/bus/usb/drivers/rt2800usb/new_i  lsmod | grep rt2800 returns the following:  rt2800usb              26581  0  rt2x00usb              20041  1 rt2800usb rt2800lib              83150  1 rt2800usb rt2x00lib              48886  3 rt2x00usb,rt2800lib,rt2800usb mac80211              545990  3 rt2x00lib,rt2x00usb,rt2800lib crc_ccitt              12627  1 rt2800lib Dual boot with windows 7! I'm using windows 7 right now. I want to install Ubuntu with dual boot. Is is safe? And does the process go safely? xml serializing of saved game data How do I reset proxy in terminal to automatic if not connected via proxy I tried to reset proxy of the terminal by some commands but it doesn't happen and automatically switches back to this proxy 172.16.0.16 (which apparently was my college proxy).   I checked in my system settings.I don't understand why this is recurring. Please be comprehensive.Also I further would like to know how to bypass proxy server since I couldn't access any of the ubuntu repositories as they were blocked in my college's proxy settings as is Ubuntu's homepage.  Thanks for your time.    For sudo ls /etc/apt/apt.conf.d/        It displays a different set of options where proxy is not listed.I am on 12.10,if this should help any.I put a snap of the terminal after the above command has been entered. Show that the free group on $n$ generators is a finite index subgroup of $F_2$ Using covering spaces, prove that for each integer $n \geq 2$, $F_n$ is a finite index subgroup of $F_2$, where $F_n$ is the free group on $n$ generators.  I get how the cayley graph of $F_n$ would be a wedge of $k$ circles and the cayley graph of $F_2$ would be a graph of a vertex and two edges, but I don't understand how we can create an injective map from $F_n$ to $F_2$ and show its a subgroup. Not all files are visible over MTP I have LG L5 (e610 model) device with Cyanogenmod 10. When I connect the phone to a computer with Linux (I have mtpfs installed), I can see both internal storage and the SD card.  However when I navigate inside them, I can't see some of the files.  For example, if I open file manager app on the phone, I can see several files in the Internal storage/Notifications directory, however the directory on the computer only shows one of those files.  If I switch USB connection type to PTP (camera) - as OS X doesn't support MTP natively - Image Capture sees the phone as a camera, however it can only see about a third of all the images present on the phone.  I don't have a Windows machine to try, but I suspect the results would be similar.  I tried upgrading Cyanogenmod to the latest nightly, clearing and reinstalling it - same results.  Any idea as to what is going on?  How can I make all files appear on the host computer? Maximize the product of the partitions of an integer Is there a possibility to make reference to the line in the lstlisting environment? I was wondering if it is possible to refer to the lines of the code enclosed in lstlisting environment rather than just manually write a number of the line I want to describe. I have never met with this feature, is this available? Is it considered normal to publish job offers inviting candidates to apply based on their gender and/or race in academia? I was browsing PhD position offers in Europe on different websites and I was quite surprised to find that several offers contained sentences such as     University of X value equality and diversity. We strongly encourage women and BAME applicants for this position.    where BAME stands for Black, Asian and Minority Ethnicities; or     The research group aims to increase the number of women in scientific positions. Female candidates are therefore encouraged to apply.   Is it considered normal in the academic environment to discriminate between  candidates according to their race and/or gender for "egalitarian" reasons?   How is the choice of a candidate based on their gender and/or race considered "egalitarian"? Legacy Debian versions and Bash Shellshock We are running Debian Etch, Lenny and Squeeze because upgrades have never been done in this shop; we have over 150 systems running various Debian versions.   In light of the "shell shock" of this week, I assume I need to upgrade bash.  I do not know Debian so I am concerned.   Can I merely execute apt-get install bash on all of my Debian systems and get the correct Bash package while my repository is pointed at a Squeeze entry. If not, what other course of action do I have? Why multiple capacitors in parallel? Wondering why you would choose to use smaller capacitors in parallel vs one bigger one.  Here's an example:      Is this a component size and track width choice?  Thanks! During Order of the Phoenix, Voldemort tries his best to lure Harry to the Ministry so that Harry retrieves the prophecy for him. In the aftermath, while Harry follows Bellatrix towards the exit, he raises a valid question:  ”Why couldn’t he (Voldemort) come and get it (the prophecy) himself?”  This is a valid question, the prophecy is labeled as referring to the Dark Lord and maybe Harry Potter. Only those mentioned can retrieve the prophecy, so Voldemort should have been able to get it, assuming he is the Dark Lord of the prophecy. Bellatrix gives a good answer:  “Get it himself?” shrieked Bellatrix on a cackle of mad laughter. “The Dark Lord, walk into the Ministry of Magic, when they are so sweetly ignoring his return? The Dark Lord, reveal himself to the Aurors, when at the moment they are wasting their time on my dear cousin?”  Despite the cackle of mad laughter, the reasoning is sound, Voldemort didn't want to reveal himself. Yet he does exactly that when he appears in the Ministry and is seen by the Minister himself, and he exposes himself for no gain. Bellatrix may or may not have been able to escape without his help, but he couldn't know that before he came, and his other followers that were captured were freed again a few months later, so it wouldn't have mattered much, he would have freed her, too. So why did he go to the Ministry and reveal himself? I want to ask how to get id of element which was clicked by right clicking in open menu. I must know ID of this element to show only that history the element what was clicked fom open menu: Is this true?  If $A$ and $B$ are sets, then $A=\emptyset $ if and only if $B = A \bigtriangleup B$.  If $A=\emptyset$ then $B=\emptyset$ too?  Could someone help me please? Mail App keeps popping up in the background in Mac OS Mojave When I am doing some work on my macbook pro, Mail app's main window keeps popping up in the background, it even pops up when I watch movies by interrupting full screen. This is so frustrating, I can't find out solution to this, googled and went to many discussion forums, no luck, suggestions that I found are very old and outdated. Has anyone faced similar issues or does anyone knows solution to this?