Determinants of Matrices det(4A) equals?
Suppose $A$ is a 4x4 matrix such that $\det(A)=\frac{1}{64}$
BJT as a switch: what am I doing wrong? How to find the sum of this series?  $$\sum_{k=0}^{\infty}\cfrac{{2}^{k}}{\binom{2k+1}{k}}$$  It seems very easy. But I still can not work it out, can anyone help? Checking to see if a user has a licence for a managed package So I'm aware that there is a method on UserInfo called isCurrentUserLicensed which lets you check if the user running the code has a licence for a namespace that you specify, i.e. for a particular managed package.  What I want to know is whether there is a way I can test to see if some other user (assume I have their ID) has a licence for a particular package. Has anybody found a way to do this? Let's say I have a generic member in a class or method, like so: public class Foo&lt;T&gt; {     public List&lt;T&gt; Bar { get; set; }          public void Baz()     {         // get type of T     }    }  When I instantiate the class, the T becomes MyTypeObject1, so the class has a generic list property: List&lt;MyTypeObject1&gt;. The same applies to a generic method in a non-generic class: public class Foo {     public void Bar&lt;T&gt;()     {         var baz = new List&lt;T&gt;();                  // get type of T     } }  I would like to know what type of objects the list of my class contains. So what type of T does the list property called Bar or the local variable baz contain? I cannot do Bar[0].GetType(), because the list might contain zero elements. How can I do it? $X$ is a topological space with no special properties.  If a space $X$ has no isolated points, then show the same for any dense subset of   $X$.  Thanks a lot. How to insert the content of a file into another file before a pattern (marker)? File1 contents:  line1-file1      "1"  line2-file1      "2" line3-file1      "3"  line4-file1      "4"    File2 contents:  line1-file2     "25"   line2-file2     "24"   Pointer-file2   "23"   line4-file2     "22"  line5-file2     "21"   After the execution of perl/shell script, File2 content should become:  line1-file2     "25"   line2-file2     "24"  line1-file1      "1"  line2-file1      "2" line3-file1      "3"  line4-file1      "4"  Pointer-file2   "23"  line4-file2     "22"  line5-file2     "21"   i.e  paste the contents of File1 in File2 before the line that contains "Pointer". Converting vector layer to raster using QGIS? In qgis in the raster menu there is an item "convert vector to raster".  This behaves strangely - I do not understand how it is supposed to work.  I can select a vector file, an attribute and an output raster. But, for some reason the output file is only accepted if it exists and even if I select an existing raster nothing seems to happen.  Also I do not understand how the program knows what kind of raster to create, what cell-size, projection etc.  How can I convert vector to raster? If HTML, CSS, and Javascript are client-side, why are they components of a PHP file? In my D&amp;D 5e campaign one of the PCs who's a wood elf started dating a dark elf, and as a result she got pregnant and she is about to give birth. One of the other players had their PC die and he is considering playing as the child of the couple.  My question is, which race is the child going to be? Why did the texture I painted in texture paint mode disappear? Find four groups of order 20 not isomorphic to each other and prove why they aren't isomorphic.   So far I thought of $\mathbb Z_{20}$, $\mathbb Z_2 \oplus\mathbb Z_{10}$, and $D_{10}$ (dihedral group), but I can't find another one. Would $U(50)$ work? I know it has order 20 and is cyclic but I'm not exactly sure how to move from there. Can someone to point me on the right direction? Creating Logo with Fancy Font I am trying to creating a logo that resembles this one shown below, but I do not know the best way of going about it. I know of a fonts package that may be useful, but not sure how to overlay the letters on top of each as so. Would anyone know a neat way of accomplishing this?  Picture of Logo: I often see output from TeX with the warning overfull hbox, badness 10000. What does this message mean? How can I produce the text Word_one_two in LaTeX?  I tried:  Samp\_Dist\_Corr   But, it doesn't quite look right. Also, I want it in the typewriter font, so actually, I'm doing:  \texttt{Samp\_Dist\_Corr}   I find it looks a bit like the underscore is merging in to the bottom of the "D", but maybe it's just because of the typewriter D? Every time I try to install "WINE" VIA the Software Center on Ubuntu 12.10, I get this error:  The following packages have unmet dependencies:  wine1.4: PreDepends: dpkg (&gt;= 1.15.7.2~) but 1.16.7ubuntu6 is to be installed          Depends: libc6 (&gt;= 2.14) but 2.15-0ubuntu20 is to be installed          Depends: wine1.4-amd64 (= 1.4.1-0ubuntu1) but 1.4.1-0ubuntu1 is to be installed          Depends: wine1.4-i386 (= 1.4.1-0ubuntu1) but it is not going to be installed   When I try installing it VIA the terminal, this is what I get:  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  wine1.4 : Depends: wine1.4-i386 (= 1.4.1-0ubuntu1) but it is not installable            Recommends: gnome-exe-thumbnailer but it is not going to be installed or                        kde-runtime but it is not going to be installed            Recommends: ttf-droid            Recommends: ttf-mscorefonts-installer but it is not going to be installed            Recommends: ttf-umefont but it is not going to be installed            Recommends: ttf-unfonts-core but it is not going to be installed            Recommends: winbind but it is not going to be installed            Recommends: winetricks but it is not going to be installed E: Unable to correct problems, you have held broken packages.   how do I fix this? How to convert numbers between hexadecimal and decimal Is it (theoretically) physically possible to project an image into thin air? How to remove trailing whitespaces with sed? What's the meaning "them" here? I've confused about the word "them" in the middle of the sentence:     They know all about them   Westovers in Idaho.   Could you please tell me what the meaning of "them" here is?     Does it mean "they know about the oils which are made by Westovers in Idaho"?   The full text is here:      Dad had always said he wanted to build a room the size of a cruise ship   but I’d never thought he’d have the money. I looked to Mother for an   explanation but it was Dad who answered. The business was a roaring   success, he explained. Essential oils were popular, and Mother had the best   on the market. “Our oils are so good,” he said, “we’ve started eating into the   profits of the large corporate producers. They know all about them   Westovers in Idaho.”   Educated by Tara Westover How to programmatically send SMS on the iPhone? Does anybody know if it's possible, and how, to programmatically send a SMS from the iPhone, with the official SDK / Cocoa Touch?