Whenever I am installing anything through the terminal, the provided code includes sudo apt-get update (to update the local repository catalog), but do we have to run the command each time we install something? Does the catalog really get updated so quickly??  This is a different question because I am asking whether I have to use the command before every install.  I am not asking what it means since I know what it means, but I don't understand the necessity of updating it every single time.
I am wondering what sudo apt-get update does?  What does it update?
What is the function of "do" in this sentence? The most common way to refer to non-immediate family? Mask and convert color in photo/video I am very new to blender still.  I want to simply change the color of an object in the video.  I want to know if there is good way to do this.  I am including what I have to test. Is it safe to eat potatoes that have sprouted? I'm talking about potatoes that have gone somewhat soft and put out shoots about 10cm long.   Other online discussions suggest it's reasonably safe and the majority of us have been peeling and eating soft sprouty spuds for years. Is this correct? How do I create a WiFi hotspot sharing wireless internet connection (single adapter)? I know how to create a hotspot when connected to a wired network, but when I am using internet from a WiFi connection, this disconnects the wireless connection the moment I activate the hotspot.  In Windows I can use , which enables me to share the internet connection from the same wireless adapter as I am creating an access point on. As you can read on the :     Access Point mode allows you to create a hotspot using the same Wi-Fi card that you are using to access the Internet.   How do I do this on Ubuntu? Am I required to pay UK/ USA Visa fees if I have a German residence permit? Here is the situation. I am non-european but staying in Germany with a Residence permit. I can visit all Schengen listed countries with no issue. Assuming that I would want to travel to a non-Schengen country e.g. UK or USA, can I use my residence permit to travel there or am I required to apply as a citizen of my country? Assuming Germans are not required to pay Visa fees to that country, will I have to pay since I only have a residence permit? Third case, Europeans can fly directly to the airport of some countries and apply for a visa from there. In some other countries, you are required to book a Visa appointment at the embassy, which may be granted or not. Does that apply for one with a residence permit? Where did object dimensions go in 2.8? I'm trying to show the following:  Let $f:X\to Y$ be a proper holomorphic map between connected, non-empty Riemann Surfaces. Show that a map $g:Y\to\mathbb{C}$ is  holomorphic if and only if  its composition with f is holomorphic.  So far I know that $f$ is surjective, since it's proper and holomorphic. My next step was to look at the charts, but it's there, I get stuck. How exactly does curved space-time describe the force of gravity? We are given with  $$S_n=\{(x,y)|x^2+y^2=n, \text{where }x,y,n \in \mathbb Z\text{ and }n\geq0  \}$$ Now observe that $-\sqrt n\leq x\leq\sqrt n $ and similarily, $-\sqrt n\leq y\leq\sqrt n $. This means that $-\left \lfloor{\sqrt n}\right \rfloor\leq x\leq \left \lfloor{\sqrt n}\right \rfloor$ and  $-\left \lfloor{\sqrt n}\right \rfloor\leq y\leq \left \lfloor{\sqrt n}\right \rfloor$. Through this result one can easily write code and figure out the cardinality of set $S_i$ but I was wondering whether an expression can be found that would allow one to directly compute $|S_i|$. Add an application to the command search path in csh Recently, I have installed an application (gnuplot) under user directory (/home/usr/bin). I want to run the application whenever I type 'gnuplot' in any directory. What could I do?  I tried to set the path in ~/.cshrc by  setenv gnuplot /home/usr/bin/gnuplot   but it doesn't work. It reports "command not found" as I type gnuplot in the terminal. How to create a timeline with LaTeX? $g^k$ is a primitive element modulo $m$ iff $\gcd (k,\varphi(m))=1$ Problem:Let $k$ be an odd positive integer. Prove that $(1+2+3...+n)|(1^k+2^k+3^k+...+n^k)$ for all positive integers $n$.  My Attempt: Proof (By Induction on $k$): Let $P(k)$ be the proposition that $(1+2+3...+n)|(1^k+2^k+3^k+...+n^k)$ for all positive integers $n$ when $k$ is odd. Then $P(1)$ and $P(3)$ are trivially true. So for $k\geq 5$, we assume that $P(k)$ holds. We would like to show that $P(k+2)$ also holds. In order to do that consider the following sums  $$1^{2}(1^k+2^k+3^k+...+n^k)=1^{k+2}+2^k+3^k+...+n^k$$ $$2^{2}(1^k+2^k+3^k+...+n^k)=2^2*1^k+2^{k+2}+2^2*3^k+...+2^2*n^k$$ $$..$$ $$n^2(1^k+2^k+3^k+...+n^k)=n^2*1^k+n^2*2^k+n^2*3^k+...+n^{k+2}$$ Note that $$1^2(1^k+2^k+3^k+...+n^k)+2^2(1^k+2^k+3^k+...+n^k)+...+n^2(1^k+2^k+3^k+...+n^k)\equiv 0\pmod {\frac{n(n+1)}{2}}$$  Therefore, if we denote $\sum_{i=1}^{n}i^2=s$, then    $(t)(1^k+2^k+3^k+...+n^k)-t+\sum_{i=1}^{n}i^{k+2}\equiv 0\pmod {\frac{n(n+1)}{2}}$ which implies that $P(k+2)$ holds. Hence by PMI we are done.  Now I am a bit hesitant in convincing myself whether this proof is correct or not. This is because I have never seen induction performed in this manner. Any reasons as to why this argument falls would be much appreciated. How do I specify unique constraint for multiple columns in MySQL? Is the $\sum\sin(n)/n$ convergent or divergent? Possible Duplicate:          So, in my calculus class (one I'm teaching, not taking), the sum $\sum_{n=1}^\infty \frac{\sin(n)}{n}$ has come up a few times.  Unfortunately, as someone not exactly an expert in the convergence of sums, it seems to resist the few techniques I know.  Certain none of the usual first year calculus tricks (integral test, alternating series test, ratio test, etc.) work, and the only more tricky technique, partial summation, I can think of doesn't seem to work either (one would need that $\sum_{n=1}^N\sin(n)$ is bounded, which I believe is false).  It seems like it should converge, since it switches sign quite often, but on the other hand, the harmonic series can mess with your intuition, so I don't have much trust in that.  So, I ask to you:     Does this series converge? Undoing a git rebase In Harry Potter and the Chamber of Secrets it is revealed that      Ginny is being possessed by Tom Riddle and is the one opening the Chamber of Secrets.   The book seems relatively without holes in this regard.  However in the movie when Harry discovers Justin Flinch-Fletchley we see moments prior to this      Ginny is studying in a room full of people.   This implies that the person opening the chamber of secrets couldn't have been in the chamber when the second attack occurs.  Is this just a goof in the movie or is there an alternate explanation for this?  Is the Basilisk acting on its own in the movie? I have a complex integral $$\int_{|z|=r}x \, dz$$ for the positive portion of the circle.  I know that this integral seems easy enough but I am having trouble with it, and I'm fairly certain my answer is incorrect.  I wanted to use a parameter such that $x=r\cos\theta$, so we then have $dz=dx+i\,dy=dx$ since there is no reason to have have the $i\,dy$ since the imaginary part is equal to $0$.  So now I have the double integral  $$\int^r_0\int^\pi_0 r \cos\theta \, dx$$  which equals $0$ since integration the $\cos\theta$ gives $\sin\theta$ and evaluated from $0$ to $\pi$ makes the integral evaluate to $0$.  Am i misinterpreting part of the question?  Way off base?  The book suggests to also solve the problem by realizing $x=\frac{1}{2}\left(z+\frac{r^2}{z}\right)$ along the circle.  For this portion of the problem I assume that I would integrate the above by $z$ as if it were a normal calculus problem, but I have problems with what to put as upper and lower limits.  Thanks in advance! Obtain user and kernel time of a running process? Is there way to determine using standard Linux/Unix tools how much a process has spent in User mode and how much waiting for kernel?  In other words, exactly the "user" and "sys" values that you get when using time, but during process runtime?  NOTE: one way is to use WBEM and enumerate Linux_UnixProcess, but I need to use other tool than this; my aim is to verify what WBEM provider tells me, i.e. I need to use different tool.