Getting the class name of an element that was clicked
Getting the ID of the element that fired an event
Can I use extra wire from two separate cables to add a washing machine in a garage? How to both display a command line's output on console and save the output into a text file? How can I run sudo apt-get install by BOTH seeing the process of installation (long in my case) and saving its output into a text file ? $P_n(x):=1+ \sum_{m=1}^n\dfrac{x^m}{m!}$ has no real root for even $n$ and exactly one real root for odd $n$ Is it true that  $$P_n(x):=1+ \sum_{m=1}^n\dfrac{x^m}{m!}$$ has no real root for even $n$ and exactly one real root for odd $n$? I can only prove that the polynomial cannot have any multiple roots. Am stuck , Please Help. Lie Algebra of U(N) and SO(N) Undefined variable problem with PHP function How would I go about detecting monopoles? A question needed for a "solid" sci-fi author: How to detect a strong magnetic monopole? (yes, I know no such thing is to be found on Earth).  Think of basic construction details, principles of operation and necessary components of a device capable of detecting/recognizing a macroscopic object emitting magnetic field of equivalent of order ~0.1-10 Tesla near its surface, but with only one pole, reliably distinguishing it from normal (2-pole) magnets, preferably at a distance.  Preferably a robust method, not involving extremely advanced technology. Detect the presence, possibly distance (or field strength) and direction.  I know of SQUIDs, but these concentrate on extreme sensitivity. I'm thinking of something less sensitive but more robust (like, no need for the monopole to fall through the loop) and still able to recognize a monopole against a magnet.  Also, how would such a macroscopic object behave practically? Such a "one-pole magnet" about the size and strength of a refrigerator magnets - how would it behave around ferromagnetics, normal magnets and so on? Could you tell me how to prove that if two series $ \sum_{n=0} ^{\infty}x_n, \sum_{n=0} ^{\infty} y_n$ are convergent, then $\sum_{n=0} ^{\infty}(\alpha \cdot x_n + \beta \cdot y_n)$ is also convergent and its sum equals $\alpha \cdot \sum_{n=0} ^{\infty} x_n + \beta \cdot \sum_{n=0} ^{\infty} y_n$? For a 3D scene in the world coordinates, its View Reference Point $\mathrm{VRP}$ is at $(5,-2,1)$, and a viewer is looking towards point $A=(1,1,1)$. Construct a transform matrix which will map world coordinate points to a right-handed $(UVN)$ viewing space, so that $\mathrm{VRP}$ is the origin, the line joining $\mathrm{VRP}$ to $A$ is the positive $N$ axis, and the view-up Vector is $(0,0,1)$.   To my knowledge, the final answer should be a single transform matrix. To calculate the final matrix, I first find the matrix which translates the coordinate system to the to the origin in homogeneous matrix form:  Translation matrix:  $$ T=         \begin{bmatrix}         1 &amp;0 &amp;0 &amp;-5 \\         0 &amp;1 &amp;0&amp; 2 \\         0 &amp;0 &amp;1 &amp;-1 \\         0 &amp;0 &amp;0 &amp;1 \\         \end{bmatrix} $$  Using the unit vectors of the coordinate axes, the resulting rotation matrix is:  $$ R=         \begin{bmatrix}         -0.6 &amp;-0.8 &amp;0 &amp;0 \\         0 &amp;0 &amp;0 &amp;1 \\         -0.8 &amp;0.6 &amp;0 &amp;0 \\         0 &amp;0 &amp;0 &amp;1 \\         \end{bmatrix} $$ Then the final matrix (the final answer for full marks) would be the rotation matrix multiplied by the translation matrix:  $$ M=         \begin{bmatrix}         -0.6 &amp;-0.8 &amp;0 &amp;1.4 \\         0 &amp;0 &amp;0 &amp;1 \\         -0.8 &amp;0.6 &amp;0 &amp;5.2 \\         0 &amp;0 &amp;0 &amp;1 \\         \end{bmatrix} $$ Is my method and final answer correct?    Following the answer to this question, I have calculated the translation matrix:  $$ T= \begin{pmatrix} 1 &amp; 0 &amp; 0 &amp; -5 \\ 0 &amp; 1 &amp; 0 &amp; 2 \\ 0 &amp; 0 &amp; 1 &amp; -1 \\ 0 &amp; 0 &amp; 0 &amp; 1 \\ \end{pmatrix} $$  I have calculated the rotation matrix:  $$ R= \begin{pmatrix} -0.6 &amp; -0.8 &amp; 0 &amp; 0 \\ 0 &amp; 0 &amp; 1 &amp; 0 \\ -0.8 &amp; 0.6 &amp; 0 &amp; 0 \\ 0 &amp; 0 &amp; 0 &amp; 1 \\ \end{pmatrix} $$  But what would the final transformation matrix $M$ be? My lecture slides tell me it would be rotation matrix multiplied by translation matrix, with the last column multiplied by $-1$ except for the $1$. This would equal:  $$ M = R \times T =  \begin{pmatrix} -0.6 &amp; -0.8 &amp; 0 &amp; -1.4 \\ 0 &amp; 0 &amp; 1 &amp; 1 \\ -0.8 &amp; 0.6 &amp; 0 &amp; -5.2 \\ 0 &amp; 0 &amp; 0 &amp; 1 \\ \end{pmatrix} $$  But the answer here just adds them together somehow. Which one is correct? What do the different colours in Ubuntu's ls command mean? For example, when I type the ls command in one of my folders, I get one of the files in light green, the other (which is a folder) in blue with green highlighting.   What do those colours mean, and there is any manual about all the colours? How to show TCP listenings and filter them by local IP on Windows? Server has numerous IP addresses, set up on it's network interface.  How to find, who is listening to specific IP port 80?  netstat shows very long list. Are there any builtin means?  UPDATE  Also can't use findstr with also wishing to know process name because brocess name is displayed on separate line. . While the reasons for his doing this are not yet public, this is a real loss of a valuable service. Does anyone know of similar services available to the general public?  Edit:  is definitely relevant, but that approach is more appropriate for finding top journals rather than identifying bottom ones. I.e., following that method would probably exclude lots of valid, lower-tier journals. Are there any approaches to easily identifying a predatory publisher? how to fix the width of the columns in the latex table? I have a table with long heading names. I want to fix the the width of the columns. When I do so the text flows out if the column. Any suggestion about fixing it.  Here is the example   \begin{table*}[ht] \begin{tabular}{|l|r|r|r|r|r|} \hline Image &amp; Score  &amp; here is a lot of text &amp; agian a lot &amp;a lot and a lot&amp; and the same here\\ \hline a \(left\) &amp; 1 &amp; 1 &amp; 1 &amp; 1 &amp; 1  \\ \hline b \(right\)&amp;  1 &amp;1 &amp; 1 &amp; 1 &amp; 1  \\  \end{tabular}  \end{table*} What is the next perfect square of the form 14444... in decimal notation? We know that $12^2 = 144$ and that $38^2 = 1444$. Are there any other perfect squares in the form of $\frac{13}{9} (10^n - 1) + 1$ (i.e. $1$ followed by $n$ $4$'s), and how would we prove it? How do I install Ubuntu to a USB key? (without using Startup Disk Creator) If you are hurrying to reply, System → Administration → StartUp Disk Creator -- no, that's not what I'm talking about.   I want to try Ubuntu 11.04's Unity without touching my existing Ubuntu install.  To do this, I need to install the nVidia drivers first (sigh).  To do this, I need changes to persist a reboot.  To do this, I need to really install Ubuntu on a USB key.  How do you do that?    What I tried   I tried to make a USB key from , then boot from it, then choose "Install Ubuntu." The installer refused to install to the installation media itself. I tried, from my installed copy of Ubuntu:  sudo kvm /dev/sdb --cdrom .cache/testdrive/iso/ubuntu_natty-desktop-i386.iso   ...but the installer didn't detect the disk properly. How to avoid bad box with long words with no hyphenation? Carry over long sequence of missing values with Postgres I have a table like this:  create table foo (foo_label text, foo_price int, foo_date date);  insert into foo (           values           ('aaa', 100,  '2017-01-01'),           ('aaa', NULL, '2017-02-01'),           ('aaa', NULL, '2017-03-01'),           ('aaa', NULL, '2017-04-01'),           ('aaa', 140,  '2017-05-01'),           ('aaa', NULL, '2017-06-01'),           ('aaa', 180,  '2017-07-01')         );   As you can see a few values on the foo_price column are missing.  What I need is that missing values get filled up with the "previous" available value in this way:   foo_label | fixed_foo_price | foo_date -----------+-----------------+------------  aaa       | 100             | 2017-01-01  aaa       | 100             | 2017-02-01  aaa       | 100             | 2017-03-01  aaa       | 100             | 2017-04-01  aaa       | 140             | 2017-05-01  aaa       | 140             | 2017-06-01  aaa       | 180             | 2017-07-01   My attempt:  select      foo_label,      (case when foo_price is null then previous_foo_price else foo_price end) as fixed_foo_price,     foo_date from (   select        foo_label,        lag(foo_price) OVER (PARTITION BY foo_label order by foo_date::date) as previous_foo_price,        foo_price,       foo_date       from foo ) T;   As you can see from here:    It doesn't fill completely the '100' series.  Any idea how can I get the wanted result? I am trying to install chrome browser via command line.  I tried this:  $ apt-cache search chrome browser   The results show that the proper term is "chrome-browser," so I tried that:  $ sudo apt-get install chrome-browser   And then "Y" for the Y/n question.  But the installation threw errors.  Does someone see anything wrong with the commands I issued? Determine if Type is a pointer in a template function Creating or adding geometry colunm fails even with postgis enabled Separate and visually indicate reversed events from the day's reputation changes We've been getting a lot of questions  ever since the feature to see event reversals such as deleted posts and serial voting was added into the reputation history; and their confusion is legitimate. Even well-respected users have become confused by that number above the day. It should display the reputation changes for that day. I propose that reversal events such as these be visually separated from the main events for that day and not included in the total reputation change for that day. After all, their reputation isn't actually changing for that day, but reversing changes from previous days. These events already seem to get bumped down to the bottom of the events for the day, why not add a simple separator between them? Events indicating reversals    Events which have been reversed     Perhaps a second, smaller number could be added next to the main one to indicate that other events took place on that day, but I feel most users who really care will have noticed or went looking for the events anyways. However, including them in the actual change only serves to confuse people.