Regarding pre-installed firefox
Why are the two versions of Chromium and VLC available in Ubuntu software of different sizes?
How can I calculate the following sum involving binomial terms:  $$\sum_{k=0}^{n} \binom{n}{k}\frac{(-1)^k}{(k+1)^2}$$  Where the value of n can get very big (thus calculating the binomial coefficients is not feasible).  Is there a closed form for this summation? Address is invalid on local machine [on windows 8 only] Reason for the current trend to use «she» as the gender-neutral pronoun? There are some questions on gender-neutral pronouns both  and on .  User Christine Letts :     In academia, there is currently a   movement toward using the feminine   pronoun at all times.   I wonder why that is. I came across several examples on papers I read, but the only one I can remember at the moment is a book: Seth Godin's . While some might not be comfortable labeling it as part of academia, it suits my point perfectly. Every time he refers to a person, he uses the feminine pronoun.  User Senseful  the following, potentially identifying affirmative action as the precursor for this trend.     I remember reading somewhere that it   was recommended to use the opposite of   what most people stereotype the   profession as. So, for example, when   talking about a chiropractor, you   would use "her", and when talking   about a secretary, you would use   "his".   So, where do you think this trend comes from? Suspected adware infection of Mac Deriving the speed of the propagation of a change in the Electromagnetic Field from Maxwell's Equations I've been told that, from Maxwell's equations, one can find that the propagation of change in the Electromagnetic Field travels at a speed $\frac{1}{\sqrt{\mu_0 \epsilon_0}}$ (the values of which can be empirically found, and, when plugged into the expression, yield the empirically found speed of light)  I'm really not sure how I would go about finding $v = \frac{1}{\sqrt{\mu_0 \epsilon_0}}$ simply from Maxwell's equations in the following form, in SI units --  $$\nabla \cdot \mathbf{E} = \frac {\rho} {\epsilon_0}$$  $$\nabla \cdot \mathbf{B} = 0$$  $$\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}$$  $$\nabla \times \mathbf{B} = \mu_0 \left( \mathbf{J} + \epsilon_0 \frac{\partial \mathbf{E}} {\partial t} \right)$$  Is what I believe true? (that the speed of propagation is derivable from Maxwell's Equations)  If not, what else is needed?  If so, can you provide a clear and cogent derivation? False proof that $ρe^{iθ} = ρ$ and so complex numbers do not exist? My professor showed the following false proof, which showed that complex numbers do not exist. We were told to find the point where an incorrect step was taken, but I could not find it. Here is the proof: (Complex numbers are of the form $\rho e^{i\theta}$, so the proof begins there) $$\large\rho e^{i\theta} = \rho e^{\frac{2 \pi i \theta}{2\pi}} = \rho (e^{2\pi i})^{\frac{\theta}{2\pi}} = \rho (1)^{\frac{\theta}{2\pi}} = \rho$$ $$Note: e^{i\pi} = -1, e^{2\pi i} = (-1)^2 = 1$$ Since we started with the general form of a complex number and simplified it to a real number (namely, $\rho$), the proof can claim that only real numbers exist and complex numbers do not. My suspicion is that the error occurs in step $4$ to $5$ , but I am not sure if that really is the case. Why on average does each bootstrap sample contain roughly two thirds of observations? Parsing an Int from a string in javascript In javascript, what is the best way to parse an INT from a string which starts with a letter (such as "test[123]")?  I need something that will work for the example below.  My JS:  $(document).ready(function() {      $(':input').change( function() {         id = parseInt($(this).attr("id"));  //fails for the data below         alert(id);     }); }   My generated HTML:  &lt;select id="attribute[123]"&gt; &lt;!-- various options --&gt; &lt;/select&gt; &lt;select id="attribute[456]"&gt; &lt;!-- various options --&gt; &lt;/select&gt;   Thank you! When there are several cottages each with several tariffs (depending on the season), should the plural be "cottage tariffs" or "cottages tariffs"?  For context, this is to be a section title on a website renting out the cottages.  An explanation of the grammatical rules would be helpful. How do I run a sudo command needing password input in the background? I have recently disabled  so that it now prompts me for a password every time.  And though this is good for security, it has caused one slight problem which I haven't been able to figure out a solution for, I am unable to run commands which go along the lines of:   sudo &lt;command&gt; &amp;   In the past I would have run a sudo command before that, it would have cached my password and allowed me to run sudo commands without prompt for the next few minutes, and thus it would allow me to run the command.  But when I run it now as there is no caching before hand and as it starts a new thread immediately and sudo doesn't even prompt me for a password, I am unable to run it in this way.  So unless I run sudo -i before it I am unable to run a command in this format which is becoming rather annoying. So I was wondering if there is any way to get around this and still run programs and commands in this way?  I am running Ubuntu GNOME 15.10 with GNOME 3.18, and specifically the program I want to run in this fashion is etherape if that makes any difference, but I would really like the solution to work for all programs and commands. How many roots have a complex number with irrational exponent? If a rational exponent on a complex number $z^q$ is the representation of a finite number of roots, then if the exponent is irrational this mean that there is infinite countable roots?  If this is the case... the cardinality of the number of roots is the same for any irrational exponent? Thanks in advance.  NOTE: there are different questions about irrational exponents but no one answer what Im searching so please dont mark this as repeated. Create a page for useful links? \RequirePackage{filecontents} \begin{filecontents}{\jobname.bib} @article{Arter95,     Author = {David Arter},     Date-Added = {2013-08-11 17:38:06 +0000},     Date-Modified = {2013-09-01 15:13:22 +0000},     Journal = {Journal of Common Market Studies},     Number = {3},     Pages = {361-287},     Title = {The {EU} {Referendum} in {Finland} on 16 October 1994:              {A} Vote for the {West}, not for {Maastricht}},     Volume = {33},     Year = {1995}}  @article{Detlef95,     Author = {Jahn, Detlef; Storsved,Ann-sofie},     Date-Added = {2013-08-11 17:14:34 +0000},     Date-Modified = {2013-08-11 17:16:45 +0000},     Journal = {West European Politics},     Number = {4},     Pages = {18-37},     Title = {Legitimacy through referendum? The nearly successful domino‚Äêstrategy of the Eu‚Äêreferendums in Austria, Finland, Sweden and Norway},     Volume = {18},     Year = {1995}} \end{filecontents} \documentclass{article} \usepackage[ngerman]{babel} \usepackage{natbib} \bibpunct{(}{)}{;}{a}{}{,} \makeatletter \renewcommand\@biblabel[1]{} \makeatother  \begin{document}  \cite{Arter95}  \bibliography{\jobname} \bibliographystyle{plainnat}  \end{document}   Please help. I want the author's name displayed like this "Arter, D." instead of David Arter Show that if $\sqrt{a}+\sqrt{b}\neq 0$, then $\mathbb{Q}(\sqrt{a}+\sqrt{b}) = \mathbb{Q}(\sqrt{a},\sqrt{b}), \forall a,b\in\mathbb{Q}$ Is my US visa still valid after change in name? I'm a Malawian national and I got US Visa years back.  Recently, due to some reasons, I had to get my first name partially changed on my passport. I have got an affidavit certificate stating the reason and proof.  Since the visa on my old passport has still not expired, but there is a difference in first name, will I face any problem? has been, have been , had been Please anyone tell me when we have to use "has been, have been , had been" and something  started in past and still continuing is it possible to use has been ? What is the difference between DX format and FX format lenses, and which to choose for what purpose? What is the difference between DX format and FX format lenses, and which to choose for what purpose?  What are the pros and cons of both? Is Checksum to file back decoding possible? So, I was having this weird thought. If the checksums(MD5 or SHA...) are unique to any file and are modified if any part of the file is edited, why cant the checksums be decoded back to get the original file? That is if I want to send a large(say 700MB) video, instead I could send just the hash and the file be decoded locally in my friend's computer. I know the thought is stupid, but is it possible by any chance? Or am I missing some thing here? And forgive me if I'm wrong, I ain't a professional. Variable importance from GLMNET Vectorization operator