Definite article with abstract nouns
Use (or non-use) of articles before abstract nouns
How to retrieve multiple rows from database in PHP Pulling a CSV file from website into QGIS with ability to automatically refresh? Explanation of method for showing that $\frac{0}{0}$ is undefined (This was asked due to the comments and downvotes on this  answer. I am not that good at maths, so was wondering if I had made any basic mistakes)  Ignoring limits, I would like to know if this is a valid explanation for why $\frac00$ is undefined:     $x = \frac00$    $x \cdot 0 = 0$        Hence There are an infinite number of values for $x$ as anything multiplied by $0$ is $0$.   However, it seems to have got comments, with two general themes.  Once is that you lose the values of $x$ by multiplying by $0$.  The other is that the last line is:      $x \cdot 0 = \frac00 \cdot 0$   as it involves a division by $0$.  Is there any merit to either argument? More to the point, are there any major flaws in my explanation and is there a better way of showing why $\frac00$ is undefined? 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? Would you please tell me which of the following terms is correct? If both are correct, are they equal?     I have no [...] I don't have any [...] Why does HMAC use two different keys? Suppose $H$ is a hash function; why is $$H(k\mathbin\|H(k\mathbin\|m))$$ not secure?  See this . In there, indeed two keys are used and the mac algorithm is $$H(k_1\mathbin\|H(k_2\mathbin\|m)).$$ Why don't we use $$H(k\mathbin\|H(k\mathbin\|m)),$$ which has only one key? How do I reference the only element in a singleton set? You can turn any element $n$ into a singleton set by adding braces, $\{n\}$. Is there an inverse to this operation, such that if I know the set is a singleton set I can easily reference its element?  For example, say I have the set $A = \{5,6,7,8\}$, and then some process that iteratively eliminates all but one element of $A$, and then I want to see what 10 plus the resulting element is, how could I write that?  The only way I can think of is by referencing the first element by its index, e.g., $10 + A_1$. Is there another way to do it though? In my case the elements of $A$ are already indices, so I would have to index an index, like $10 + x_{A_1}$. Which is not the worst thing in the world, I was just wondering if there is a better way. Aiming at specific body parts I have tried as following:  1. Turn off: export DISPLAY=:0.0 &amp;&amp; xset dpms force off  2. Turn on: export DISPLAY=:0.0 &amp;&amp; xset -dpms   Which works but that is a temporary solution, which does not fix my problem yet. When i reboot system it start again and again the same auto turn off mode.   How can i now remotely using SSH turn it off forever?  IMPORTANT:  - KIOSK (ATM machine will use this option) - 24/7 advertising display/slides will use this   Optional Note: this guide i followed   , but permanent solution did not worked. I remember being taught that the correct order of adjectives in English was something along the lines of "Opinion-Size-Age-Color-Material-Purpose."  However, it's been a long time and I'm pretty sure I've forgotten a few categories (I think there were eight or nine). Can anyone fill them in? Quaternion for beginner I have 2 points in 3d space ,point A= &lt;5,3,6> and B=&lt;8,2,3>  I want to rotate "point B" by 30 degree from point A.  how do I solve this question using quaternion.  Plz, explain the steps.... How to exclude/delete files only? Is there a way to exclude all files, in all subfolders, and keep the folder structure? Determinant of block matrix with commuting blocks I know that given a $2N \times 2N$ block matrix with $N \times N$ blocks like   $$\mathbf{S} = \begin{pmatrix} A &amp; B\\  C &amp; D \end{pmatrix}$$  we can calculate $$\det(\mathbf{S})=\det(AD-BD^{-1}CD)$$ and so clearly if $D$ and $C$ commute this reduces to $\det(AD-BC)$, which is a very nice property.   My question is, for a general $nN\times nN$ matrix with $N\times N$ blocks where all of the blocks commute with each other, can we find the determinant in a similar way? That is, by first finding the determinant treating the blocks like scalars and then taking the determinant of the resulting $N\times N$ matrix.  Thanks in advance! Invoking JavaScript code in an iframe from the parent page Basically, I have an iframe embedded in a page and the iframe has some  routines I need to invoke from the parent page.  Now the opposite is quite simple as you only need to call parent.functionName(), but unfortunately, I need exactly the opposite of that.  Please note that my problem is not changing the source  of the iframe, but invoking a function defined in the iframe. Repeat each line multiple times Would like to have each line in a file repeated a fixed number of times.  e.g. have each line repeated four times:  a b c   becomes:  a a a a b b b b c c c c   I've done some searching, and there are a lot of questions and answers along the lines of doing the reverse, e.g. merging duplicate lines into single lines, and maybe a few about doubling lines by printing them again.  It would be easy to do this in C, but I wish I knew more about the native commands so I wouldn't have to resort to these kinds of one-off throw-aways all the time. How to replace a video on YouTube I need to make a small correction in a video I uploaded to YouTube. Googling shows that this is not possible. However, I remember seeing it done before. I posted a comment on a video saying that a certain part of the video was missing. I got a reply back that it was fixed, and when I went to see the video again, it was changed. How was this done? Given a $10×10$ grid with $9$ red blocks and $91$ white blocks, in each step we color one red block black and after that one white block red until there are $91$ black blocks and $9$ red blocks. Prove that there exits a step in which a black block shares an edge with a white block. I ran a few trials and couldn't get past the fifth step without adjacency. But I don't know how to build a proof. Undoing a git rebase What to do after visiting unsafe site As seen in this video: (Skip to 5:53)  When a player is slain, they drop an Enchanting Table on top of their inventory.  How was this achieved and how can I build a system (using command blocks) that does that? Come to think of it, what happens to a player's location when he/she dies? Does it reset to the spawnpoint? Stay the same (where they died) until they respawn? Or becomes a null value until they respawn?