How make Safari always download CSV files instead of opening them in-page?
Fine-tuning "Open safe files after downloading"
PHP MySQLi doesn't recognize login info I'm trying to prove that  $$ \left| \frac{1}{x}-\frac{1}{y} \right| $$  is a metric on $X = \mathbb R^+$.  The properties of non-negativity and symmetry are obvious (do I actually even need to prove them?), but the tricky one is, as usual the inequality property, i.e.  $$ d(x,z) \le d(x,y) + d(y,z) \text{ for any } z \in X. $$  So, ok, I have that  $$ d(x,z) \le d(x,y) + d(y,z) \\ \iff \left| \frac{1}{x}-\frac{1}{z} \right| \le \left|\frac{1}{x} - \frac{1}{y} \right| + \left|\frac{1}{y} - \frac{1}{z} \right| \\ \iff \left| \frac{1}{x} \right|- \left| \frac{1}{z} \right| \le \left| \frac{1}{x}-\frac{1}{z} \right| \le \left|\frac{1}{x} - \frac{1}{y} \right| + \left|\frac{1}{y} - \frac{1}{z} \right| $$  ...and that's about as far as I've gotten–which is to say, not very far. I also tried multiplying both sides by $ \left| \frac{1}{x}-\frac{1}{z} \right| $, but that wasn't very fruitful. If someone could point me in the right direction, it'd be greatly appreciated. Thanks. I have been attending a number of academic / professional conferences recently and one thing that really awed me was the flawless and natural way in which the speakers presented on their topics.  Sure, they had the occasional mispronunciations or awkward pauses but they spoke with authority and confidence.   Some of them used powerpoint slides but were not reading from the slides; they were just talking on the points and they had so much to say on each point that I felt they could not do it without notes, but they were not even looking at their notes most of the time.  (The advantages of not looking at their notes too much was that they could maintain eye contact and could use very interesting slides that were not crammed with the dot points of their speeches.)  I hate to think that they had memorised their speech notes but some of the presentations went for more than an hour.  I know rehearsal is important but I wonder how could anyone remember so much in a nervous situation. (Its one thing to know everything on your topic; its another thing to present that 'everything'!)  Question:  What background / foreground things do presenters do that make their presentations flawless and natural? Search using symbols is broken We used to be able to , but that now appears to be broken.  I'd expect a  to return a result, but instead the search engine appears to put quotes around the whole request; the search box shows the search has been replaced with "[python] += list" and the  I was looking for doesn't appear among the returned questions.  Using quotes around the symbols do not seem to help here;  returns an empty result. Prove: $$ (a+b)^\frac{1}{n} \le a^\frac{1}{n} + b^\frac{1}{n}, \qquad \forall n \in \mathbb{N} $$ I have have tried using the triangle inequlity $ |a + b| \le |a| + |b| $,  without any success. Playing a remote movie on the remote computer Compactness of  Multiplication Operator on $L^2$ Suppose we have an bounded linear operator A that operates from $L^2([a,b]) \mapsto L^2([a,b])$.  Now suppose that $A(f)(t) = tf(t)$.    Is A compact?  Edit: I know $A = A^*$ but I'm not really sure how to start on this.  It's not homework, just summer fun :D How can the median number of sexual partners be 6.1 and 3.6? Median number of female sexual partners in lifetime, for men 25-44 years of age, 2006-2008: 6.1  Wouldn't it only be able to be x.5 or x.0? Word for someone who repeats words Why does Windows only show about 3.5 GB of my 4 GB of RAM? I'm trying to make a systemd timer that runs every 15 minutes. Right now I have:     timer-fifteen.timer:  [Unit] Description=15min timer  [Timer] OnBootSec=0min OnCalendar=*:*:0,15,30,45 Unit=timer-fifteen.target  [Install] WantedBy=basic.target    timer-fifteen.target:  [Unit] Description=15min Timer Target StopWhenUnneeded=yes    This runs over and over again without stopping. Does it need to be *:0,15,30,45:* instead? How can I make this work? What is this lock screen with ads and how do I remove it? I think my device got a malware. A lock screen with ads sometimes appear, and I must swipe an area at the bottom of the screen to open the phone. I am in Eastern Europe, some ads are in Slavic languages, and they are seemingly related to travel.    Image resized. Click to view the full image  I have seen ads for Lot Air (Polish carrier). I recently went to their site.  Considering my recent surfing activity and the nature of the ads, I guess the malware is connected to airlines active in Eastern Europe.  The lock screen also promotes the app "DU Quick Charger" by claiming it has recharged the phone extra fast during screen off. (!?) It also shows battery level. I have never installed DU Quick Charger. I doubt DU Quick Charger is installed on the phone.  The problem started after installing Ryanair app. The problem is maybe, but not surely, related to this. Uninstalling Ryanair and restarting the phone doesn't remove the occasional appearance of this lock screen. After a while the situation has changed for the worse, now this lock screen appears after EVERY screen off.  I have always used Avast. I am not rooted and only install via Google Play.  What is this? And how do I remove it? Why CTRL + C multiple times I have recently noticed that I press CTRL + C more than once, even if I know that the file has been copied to the clipboard. But I press CTRL + X or CTRL + V only once.   Why do I do this? Is this only a problem for me, or is anybody else is facing it too? Is my paper under review (or similar) for too long and if yes, how should I react? I submitted a paper to a journal, and I suspect that it is handled too slowly.   How can I decide whether my suspicion is correct? What handling times should I expect? Given some expected handling times, when should I act? How much leeway should I give? How should I act? Whom should I contact and what should I (roughly) write?   Note that I am interested on how I should approach this situation in general, and do not seek specific numbers for my specific situation. I am therefore looking for general answers that are independent of such factors as the field or individual journal (but mention them if they are relevant factors).  This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question. Cannot determine size of graphic I'm trying to include graphics in my Latex-file, which I compiled with latex+dvipdf on OS X. Latex however returns this error: "Cannot determine size of graphic"  My graphic is exported from PowerPoint, so I have tried both .pdf and .png. I get the same errors for both.  Sample code that doesn't work:  \begin{figure}[htb] \begin{center} \leavevmode \includegraphics[width=0.8\textwidth]{graph.png} \end{center} \end{figure}   If I have to manually set some measurements of the image, please tell me how I can find out those measurements. I need the image to take up about 80% of text width and be centered. Thanks. How can I check if a directory exists in a Bash shell script? What command can be used to check if a directory exists or not, within a Bash shell script? When is using the past perfect tense not necessary? Is it more natural to speak in simple past or past perfect when explaining past events to a friend? It seems like Americans use more simple past in everyday life than past perfect. I found this example online:     I had almost completed my essay when my computer suddenly crashed and I noticed that I had forgotten to save the document.   Is it wrong to say the following instead?     I was almost done with my essay when my computer suddenly crashed and I noticed that I forgot to save the document.   Maybe it's just my friends, but I rarely hear them speak in past perfect, so I'm really torn about using past perfect when it isn't necessary. Is it wrong to place the  tag after the  tag? Copy files excluding x,y,z causing error in shell script I'm not well versed in shell scripting but I imagine this to be a painfully easy fix but its eluding me.  I need to copy the contents of a directory excluding a number of files. I have a command that works when I enter it into the terminal, but when its run in a shell script it fails with a syntax error or just doesn't work.   The command in question is:  cp -r path/to/!(dir1|dir2|dir3) destination   Any help would be greatly appreciated! Cartesian product of two $\sigma$-algebras is generally not a $\sigma$-algebra? When reading the book Measures, Integrals and Martingales written by R.L. Schilling, I saw a statement as below: $$\mathcal{A} \times \mathcal{B}:= \{A \times B: A\in \mathcal{A}, B\in \mathcal{B}\}$$ where $\mathcal{A}$ and $\mathcal{B}$ are $\sigma$-algebras, is not $\sigma$-algebra in general.  However, I cannot construct a counterexample. Could anyone offer help here?  Kind regards