Attendance tracking in Excel
How do I count attendance in Excel?
Why don't Muggle-born wizards use Muggle technology to fight Death Eaters? How can we sum up $\sin$ and $\cos$ series when the angles are in arithmetic progression? How can we sum up $\sin$ and $\cos$ series when the angles are in arithmetic progression? For example here is the sum of $\cos$ series:  $$\sum_{k=0}^{n-1}\cos (a+k \cdot d) =\frac{\sin(n \times \frac{d}{2})}{\sin ( \frac{d}{2} )} \times \cos \biggl( \frac{ 2 a + (n-1)\cdot d}{2}\biggr)$$  There is a slight difference in case of $\sin$, which is: $$\sum_{k=0}^{n-1}\sin (a+k \cdot d) =\frac{\sin(n \times \frac{d}{2})}{\sin ( \frac{d}{2} )} \times \sin\biggl( \frac{2  a + (n-1)\cdot d}{2}\biggr)$$   How do we prove the above two identities? I would like to know difference between user and service account.  I know that e.g. Jenkins installed to ubuntu is not a user, .    What is use of service account? When we need them? How can I create service account? Pretty tricky cmd How to install H.265 / HEVC codec on Ubuntu Linux? I have seen that the new  shows off H.265/HEVC playback, the successor of H.264. I wonder how I may get this support in Linux. Is there a need to install a codec specific for this format? How? "Pick up something" or "pick something up"? I have a Virtual machine using centos 7 with 200GB disk.For some reason my layout is:  df -h Filesystem               Size  Used Avail Use% Mounted on /dev/sda1                100GB  95GB  5GB      Running fdisk -l:  Disk /dev/sda: 204.8 GB, 204803670016 bytes,400007168 sectors  Units = sectors of 1 * 512 = 512 bytes  Sector size(logical/physical): 512 bytes / 512 bytes I/O size(minimum/optimal): 512 bytes / 512 bytes Disk label type: dos Disk identifier: 0x0006c283  Device Boot      Start         End      Blocks   Id  System /dev/sda1            2048   199997439    99997696     Linux   I would like to increase my space on my partision /dev/sda1. Negative y value in polar plot I'm having some trouble with polar plots. I have to plot negative values, but without changing direction. I tried to set the ymin value to be negative, but it doesn't work.  \documentclass[10pt,border=10pt]{standalone} \usepackage{pgfplots} \usepgfplotslibrary{polar}  \begin{document} \begin{tikzpicture} \begin{polaraxis}[    xticklabel=$\pgfmathprintnumber{\tick}^\circ$,    ymin=-10,    xtick={0,30,...,330}] \addplot table{    0  -1     30 -2    45 -3    60 -4    75 -5    }; \end{polaraxis} \end{tikzpicture} \end{document}   Any suggestion?  For clarity, this is what I expected. How does the 'passwd' command gain root user permissions? How does Linux know that it has to give euid 0 (uid of root) to only certain process like passwd, setuid, etc.  If a process can gain root permissions, will it not lead to potential security breaches in the Linux platform?   For example, if I write a program that can can gain root user permissions like passwd, I may corrupt important system files like /etc/passwd, /etc/groups.   How does Linux manage to still be secure? Polynomials with integer coefficients such that $p(a)=b,p(b)=c,p(c)=a$ While studying polynomials a question struck in my mind that  To have a polynomial $p(x)$ with integer coefficients and $a,b,c$ are three distinct integers, then is it possible to have $$p(a)=b$$$$p(b)=c$$$$p(c)=a$$ In Einstein's General Relativity, do the space-time dimensions curve? In Einstein's General Relativity, do the space-time dimensions curve according to the positions of stars, planets, and masses? Why are our planets in the solar system all on the same disc/plane/layer? I always see pictures of the solar system where our sun is in the middle and the planets surround the sun. All these planets move on orbits on the same layer. Why? How can I make Ubuntu 18.04 / 18.10 desktop use Unity (be like Ubuntu 14.04)? How to place a .png texture with transparency over a material Can a satellite remain directly over a city? Is it possible to put an artificial satellite into an orbit in such a way that it will always remain direct over a city (I mean at any specific place)? Without appealing to choice, can we prove that if $X$ is well-orderable, then so too is $2^X$? Without appealing to the axiom of choice, it can be shown that (Proposition:) if $X$ is well-orderable, then $2^X$ is totally-orderable.  Question: can we show the stronger result that if $X$ is well-orderable, then so too is $2^X$?  Proof of Proposition. Pick any well-ordering of $X$. Then the lexicographic order totally orders $2^X$.  More explicitly: for any two $f,g \in 2^X$, define $f &lt; g$ iff   there exists $x \in X$ such that $f(x) \neq g(x)$, and if $x \in X$ is minimal such that $f(x) \neq g(x)$, then $f(x)=0$ and $g(x)=1$.   It can be shown that $&lt;$ totally-orders $2^X$. Proving the sum of two independent Cauchy Random Variables is Cauchy How to use x coordinate of a point and y coordinate of other point? Possible Duplicate:             How to use x coordinate of a point and y coordinate of other point? I need similar to  \coordinate (A) at (2,1); \coordinate (B) at (3,0); \coordinate (C) at (4,3); \coordinate (D) at (5,-1);  \draw (xA,yB) -- (xC,yD); I am a economics major undergraduate student who will apply for grad schools in the coming semester. I think I have quite a strong research experience in mathematical statistics (asymptotic statistics to be specific), but, unfortunately, not much in economics itself. So I am curious if economics departments in graduate schools will care about my research experience in statistics?  Maybe a broader question is if grad schools care about applicants' research experience in a different (maybe even unrelated) field at all? I guess in my case statistics and economics are still quite correlated, but what about other more distant combinations of target departments and previous research experience? How to evenly space vertices? I have a edge loop that has vertices on it. Is there a way I can separate the vertices on the the edge evenly without moving the end points? I would also like for the vertices to maintain the current shape.