How to cycle windows of the same app on Czech keyboard layout
Shortcut for toggling between different windows of same app?
Prove that if $n$ is a composite, then $2^n-1$ is composite. Not sure if I'm doing this correctly but this is what I've done:  Assume that $n$ is composite and suppose $2^n-1$ is a prime for $n \gt 2$. Then, $2^n-1 = 2k$ for some $k \in \Bbb Z $, $\forall n$.  But this would be a contradiction since $n \gt 2$.  I'm not sure if this a correct proof.  EDIT: I realized that it's to prove $2^n - 1$ NOT $2^{n-1}$ so my attempt above is completely wrong. Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$? Counter ions and charge of a complex how can I add the charge and the counter ions to my complex? I'm using chemfig.  \schemestart \chemname{\chemleft[\chemfig{Ni (&lt;:[1]OH_2) (-[2]OH_2) (&lt;:[3]OH_2) (&lt;[5]OH_2) (-[6]OH_2) (&lt;[7]OH_2) }\chemright]}{\ce{[Ni(OH2)6]Cl2}} \schemestop     Thanks! Is "education" a count noun? Can spells with movable areas of effect be moved out of sight or behind obstacles? With spells like Moonbeam or Flaming Sphere, how should we treat the movement of their areas-of-effect when it comes to passing them behind a thick pillar or around a blind corner?  Should we treat any movement of them as if they are being 're-cast' (and so requiring a clear unobstructed view)? Or could a mage presumably will them somewhere out-of-sight? I listened to this on audiobook and it was great.  The premise was a human ends up travelling to an alien planet. The aliens have a perimeter to their 'base' that is under constant attack from the planet's animals. It is revealed towards the end that there is some sort of signal being transmitted that is making all the animals and plant life attack a certain point on the planet (where the aliens are).   Other major plot points I remember: The human traveller falls in love with an alien. The aliens have a sort of virtual training environment that simulates life outside the perimeter, where plants attack you etc. There is a secondary alien group that the human ends up with, and although they are rivals to other group, they have a trade set up.   Any help much appreciated! Thanks. When does function composition commute? I've read that function composition "generally does not commute."  Not counting compositions involving the identity function, and compositions of a function and its inverse, are there examples of functions on the reals (for example) $f, g$ where $fg = gf$ outside of these cases? Is it possible to create a URL link to a website on the home screen? Which are the standard commands available in every Linux based distribution? If $0<a<b$, prove that $a<\sqrt{ab}<\frac{a+b}{2}<b$ Using \@-ified punctuation while using \frenchspacing After reading  about spacing and punctuation, I was left wondering about an issue that didn't seem to be addressed: using \frenchspacing together with the modified punctuation \@., \@?, etc.  As far as I can tell visually, using \frenchspacing together with these commands works correctly (i.e., it seems like nothing breaks, and the extra space is suppressed as normal), but are there problems that can arise from doing so?   Moreover, when using \frenchspacing, "should" I still use \@. and its friends where it would ordinarily be necessary, in case someone wants to remove \frenchspacing later? Would accommodating (hypothetical) future editors in this way be "standard", "above and beyond the call of duty", or "crazy"? I have few friends.   I have a few friends.      I thought "few" means just one, two or even none. "A few" typically means more than two. However it seems to me some people say "few" when they really mean "a few", am I right? Greek pdf bookmarks I am puzzled with sections titled with Greek characters. They do appear in the pdf's Content list, though not correctly.  For example, in my thesis--written in English with LyX, based on the KOMA-script--I choose to include a translation of the summary in Greek (=Περίληψη). The "raw" code for the (unnumbered) chapter title reads: \addchap{\textgreek{Per\char208lhyh}}. In the final .pdf file (using pdflatex) the respective entry appears as Per208lhyh. Using the unicode option for the hyperref package does not fix the problem.  Update detail: the document (should) not only contain Chapter or Section titles in Greek, but normal text as well.  I have found some relevant references within tex.stackexchange and elsewhere (e.g., , the manual of the textgreek package, , ). However, I cannot extract a concrete answer.  How can Greek characters appear correctly as bookmarks in the .pdf's Content list?  Note, the information of this Q&amp;A applies to/under LyX as well. Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop NFS: mount.nfs: Protocol not supported According to my logic,  $$\large\sqrt{x^2} = x^{2\times \frac{1}{2}} = x = x^{\frac{1}{2}\times 2}={(\sqrt{x})}^2$$  But when I look at the graphs of these guys, they're totally different.  Edit: Complex answers are okay, if you know what I mean. apt-get install vs pip install I am a bit confused about the cases in which the above commands must be used when downloading python packages. I was trying to download a package named pyudev in accordance with an answer with this . I executed this command :  sudo pip install python-pyudev   but received the following message :  Downloading/unpacking python-pyudev    Could not find any downloads that satisfy the requirement python-pyudev Cleaning up... No distributions at all found for python-pyudev Storing complete log in /home/vineet/.pip/pip.log   However the following worked fine :  sudo apt-get install python-pyudev   When is apt-get supposed to be used to install packages and when is python-pip used? Dynamically creating keys in a JavaScript associative array All the documentation I've found so far is to update keys that are already created:  arr['key'] = val;  I have a string like this: &quot; name =  oscar &quot;  And I want to end up with something like this: { name: 'whatever' }  That is, split the string and get the first element, and then put that in a dictionary. Code var text = ' name = oscar ' var dict = new Array(); var keyValuePair = text.split(' = '); dict[ keyValuePair[0] ] = 'whatever'; alert( dict ); // Prints nothing. This question, , seems to indicate $$\nabla_a \sqrt{g}=0.$$ Why is this the case? I've always learned that $$\nabla_a f= \partial_a f,$$ hence surely $$\nabla_a \sqrt{g}=  \partial_a\sqrt{g} \neq 0. $$  Where's the hole in my logic? Questions with many upvotes should not be closable I see a lot of good, well-writen and constructive questions (that are probably not only good for me) closed, by various reasons which I fail to digest, so I propose the idea that questions with n upvotes should not be closable.  This would be in my opinion very much in the spirit of "", and unless I'm wrong, it would be beneficial for the users to choose by themselves whether the site should have or not x question. The ones which are low quality never get many upvotes anyway.  The only cons I can think of are... DB space? And at a minimum there's the pro of more popular pages with more ads (for the admins), and questions people like (for the users).  I'm also counting for , in the lines of Google's "", but questions  are more like what I'm aiming at (probably that question has not many upvotes for this though).