I am very new to Ubuntu and trying to install some soundfonts. One of them is in .rar. Do any of you know a way to open this type of fiel and make it operational?  Thanks,  Martin
I just realized I can't unrar .rar files on my Ubuntu machine!  What's the easiest way to accomplish this fundamental task? If possible I'd love something like 7Zip that I can just right Click, and extract and have the program worry about how to do it regardless if it's a .zip, a .rar or a .foo compressed file.
A is similar to $A^k$, then each eigenvalue of $A$ is a root of unity Let $A \in \mathbb{C}(n,n)$ and $k \geq 2$ be an integer such that $$A \sim A^k$$. Show that if $A$ is non-singular then each eigenvalue of $A$ is a root of unity.   Attempt: Since $A \sim A^k$, $$PA = A^kP$$ where $P$ is an invertible matrix. Since $A$ is invertible, $0$ cannot be an eigenvalue of $A$. Suppose $$Av = \lambda v \quad v \neq 0$$ then $$PAv = \lambda Pv$$ $$\therefore A^k(Pv) = \lambda (Pv) $$ but this implies that $Pv$ is an eigenvector of $A$. But the eigenvalues of $A^k$ are $\lambda^k$ $$\therefore \lambda^k=\lambda$$ which gives the conclusion required.   My questions is: Is the logic correct? If so, Am I missing any details? If not, then how could I approach this?   Thanks! Is there an irrational number $a$ such that $a^a$ is rational? It can be proved that there are two irrational numbers $a$ and $b$ such that $a^b$ is rational (see ) and that for each irrational number $c$ there exists another irrational number $d$ such that $c^d$ is rational (see ).  My question is: Is there an irrational number $a$ such that $a^a$ is rational (and how could you prove that)? How exactly does Knuth's Up-Arrow notation work? I've done some research, and found this on Wikipedia. \begin{matrix}a\uparrow b=a^{b}=&amp;\underbrace {a\times a\times \dots \times a} \\&amp;b{\mbox{ copies of }}a\end{matrix} \begin{matrix}a\uparrow \uparrow b&amp;={\ ^{b}a}=&amp;\underbrace {a^{a^{{}^{.\,^{.\,^{.\,^{a}}}}}}} &amp;=&amp;\underbrace {a\uparrow (a\uparrow (\dots \uparrow a))} \\&amp;&amp;b{\mbox{ copies of }}a&amp;&amp;b{\mbox{ copies of }}a\end{matrix} I'm still a bit confused on this topic. I've done a lot of research, but I can't seem to understand this. Could somebody explain this in an understandable way? From what I can gather, for example 2↑↑3 would be 2^2^2 = 16? Then 2↑↑↑3 would be 2^2^2^2 = 256? Am I correct, or have I mis-interpreted this? ext4 partition size / free space discrepancies While creating a 250GiB backup partition for my data, I have noticed lots of discrepancies between reported partition size and free space in Nautilus, gParted, df, tune2fs, etc.  At first I thought it was a GiB / GB confusion. It was not.  Then I thought it could be ext4's reserved blocks. It was not.  Im completely puzzled. Here are some images. Here are the steps:   First, NTFS. 524288000 sectors x 512 bytes/sector = 268435456000 bytes = 268.4 GB = 250 GiB.      Nautilus say "Total Capacity: 250.0 GB" (even though its actually GiB, not GB). Apart from that minor mislabeling, so far, so good   Now, same partition, formated as ext4 with gparted:     First, Last and Total sectors are the same. It IS the same 250GiB partition. Used size is 4.11GiB (reserved blocks maybe?)    Nope. Looks like reserved blocks are 12.7 GiB (~5%. ouch!). But... why Total Capacity is now only 246.1 GiB ???. That difference (sort of) matches the 4.11 GiB reported by gparted. But... if its not from reserved blocks, what is it? And why gparted didnt report that 12.7GiB of used space?  $ df -h /dev/sda5 Filesystem            Size  Used Avail Use% Mounted on /dev/sda5             247G  188M  234G   1% /media/BACKUP   df matches Nautilus in reported free space. But.. only 188M used? Shouldnt it be ~12GB? And total capacity is still wrong. So i ran tune2fs to find some clues. (irrelevant output is ommited)  $ sudo tune2fs -l /dev/sda5 tune2fs 1.41.12 (17-May-2010) Filesystem volume name:   BACKUP Filesystem UUID:          613d592e-47f5-4206-96a7-210090d340ef Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags:         signed_directory_hash  Filesystem state:         clean Filesystem OS type:       Linux Block count:              65536000 Reserved block count:     3276800 Free blocks:              64459851 First block:              0 Block size:               4096   65536000 total blocks * 4096 bytes/block = 268435456000 bytes = 268.4 GB = 250 GiB. It matches gparted.  3276800 reserved blocks = 13421772800 bytes = 13.4 GB = 12.5 GiB. It (again, sort of) matches Nautilus.  64459851 free blocks = 264027549696 bytes = 264.0 GB = 245.9 GiB. Why? Shouldnt it be either 250-12.5 = 237.5 (or 250-(12.5+4.11)=~233) ?  Removing reserved blocks:  $ sudo tune2fs -m 0 /dev/sda5 tune2fs 1.41.12 (17-May-2010) Setting reserved blocks percentage to 0% (0 blocks)  $ sudo tune2fs -l /dev/sda5 tune2fs 1.41.12 (17-May-2010) Filesystem volume name:   BACKUP Filesystem UUID:          613d592e-47f5-4206-96a7-210090d340ef Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags:         signed_directory_hash  Filesystem state:         clean Filesystem OS type:       Linux Block count:              65536000 Reserved block count:     0 Free blocks:              64459851 Block size:               4096   As expected, same block count, 0 reserved blocks, but... same free blocks? Didnt I just freed 12.5 GiB ?  $ df -h /dev/sda5 Filesystem            Size  Used Avail Use% Mounted on /dev/sda5             247G  188M  246G   1% /media/BACKUP     Looks like I did. Avaliable space went up from 233 to 245.9 GiB. gparted didnt care at all, showing exactly same info! (useless to post an identical screenshot)  What a huge mess!  I tried to document it as best as I could... So, please can someone give me any clue on what's going on here?   What are those misterious 4.11 GiB missing from NTFS -> ext4 formatting? Why there are so many discrepancies between gparted, Nautilus, tune2fs, df? What is wrong with my math? (questions in bold scattered this post)   Any help is appreciated. While I can not figure what is going on, I am serilously considering giving up on ext4 in favor of NTFS for everything but my / partition.  Thanks! Suppose $f:\mathbb{R}\to\mathbb{R}$ is Borel measurable. I want to show that $\displaystyle \int_a^b f(x)\mathrm dx=0$ for all $-\infty&lt;a&lt;b&lt;\infty$ with $a$ and $b$ rational implies that $f=0$ a.e. I'm really not sure how to approach this problem; any help would be welcome. How to install Chromium without snap? I just discovered that chromium will only be released as a snap package.  How can I continue to get chromium, without snap? Is this possible without building from source?  Notes:   Please let's keep to the question as stated - not "what do you have against snap?" I'm not asking how to remove snap (I realize that would break Ubuntu)... just how to use chromium as it is now, a deb.     Update  No, this is not a duplicate of that linked question. I don't need to know "why it's a snap". I want to know how to use it without snap.  Right now there is building from source, and some random PPA mentioned below. I hope someone can advise us of trustworthy alternatives. Possessive Form of a Proper Noun Ending in a Plural Noun Ending in "s"? I don't think this has yet been covered in .  There was , however, it was not specifically talking about the case where the proper noun ends in a plural noun.  Feel free to vote to close if I am wrong.  What is the correct way to make a proper noun ending in a plural noun ending in an "s" possessive?  This frequently happens with corporations, e.g., "Dunkin' Donuts."  Should one work off of the fact that the entity is singular—suggesting Dunkin' Donuts's—or should one work off of the fact that "Donuts" is plural and ending in an "s"—suggesting Dunkin' Donuts'?  I expect that the answer might depend on dialect because some regions refer to corporations in the singular form ("Dunkin' Donuts is a company") while other regions refer to corporations in the plural form ("Dunkin' Donuts are a company").  I am specifically interested in American English, but would be interested in hearing answers for other dialects too. Upon the risk of being down voted as no MWE is present, but at the moment just trying to get some pointers. I updated my MiKTeX installation to the newest available version at the moment (MiKTeX-pdfTeX 4.1 (MiKTeX 20.12)) and now I get an error while building my documentation: Appendix D. (../html/examples/group/latex/refman_doc.tex (../html/examples/group/latex//gro up__group1.tex) [243] ! I can't write on file `../html/examples/group/latex//group__group2.aux'. \@include ...mmediate \openout \@partaux &quot;#1.aux&quot;                                                   \immediate \write \@partau... l.3 \include{group__group2}  Please type another output file name ! Emergency stop. \@include ...mmediate \openout \@partaux &quot;#1.aux&quot;                                                   \immediate \write \@partau... l.3 \include{group__group2}  *** (job aborted, file error in nonstop mode)  some small background:  Started normally with pdflatex doxygen_manual.tex in here is the statement: \subinputfrom{../html/examples/group/latex/}{refman_doc} and in this file again: \include{group__group2} as far as I know the disk is not full and the protections of the files and directories are OK as well  It looks like that now an attempt is made to write to the directory ../html/examples/group/latex/ whilst in the past the file was written to the current directory. I already tried -shell-escape and -enable-write18 (as well as --shell-escape and --enable-write18) but to no avail.  Any known changes in respect to writing the aux file? Any hints  edit I asked another question () with the details and MWE but that was closed with the reason that it was a duplicate of this one ... So I'm adding the information now here: In the question  asked about the problems I encountered due to an update of my MiKTeX distribution, but didn't take the time (at that moment) to create a MWE, so it didn't attract much response. I have the directory structure:  main  manual.tex   group  group__group2.tex refman_doc.tex    manual.tex \documentclass{book} \usepackage{import} \usepackage{hyperref}  \begin{document} \subinputfrom{../group}{refman_doc} \end{document}  group__group2.tex \hypertarget{group__group2}{}{The Second Group}  refman_doc.tex {Module Documentation} \include{group__group2}  When running in the directory main the command pdflatex manual.tex I get the error: ... (../group/../group/refman_doc.tex [1{C:/Users/User/AppData/Local/MiKTeX/2.9/pdf tex/config/pdftex.map}] ! I can't write on file `../group//group__group2.aux'. \@include ...mmediate \openout \@partaux &quot;#1.aux&quot;                                                   \immediate \write \@partau... l.2 \include{group__group2}  Please type another output file name:  but in a non interactive mode (the usual way to run. i.e. with \batchmode) one doesn't get an opportunity to specify the file and the generation crashes. As written in the original question adding options like -shell-escape and / or -enable-write18 didn't help.  Is there a solution for this problem?  edit 2 I did some further test. I replaced the \subinputfrom with an \input statement, although this worked for the limited example above it didn't work for my larger codebase as here (again just a limited view) we have in the refman_doc.tex {Module Documentation} \input{group__group1} \include{group__group2}  with the contents of group_group1.tex similar to group__group2.tex and the file is also parallel to group__group2.tex. This results in the error: (manual.out) (manual.out) (../group/refman_doc.tex  ! LaTeX Error: File `group__group1.tex' not found.  Type X to quit or &lt;RETURN&gt; to proceed, or enter new name. (Default extension: tex)  Enter file name: ! Emergency stop. &lt;read *&gt;  l.2 \input{group__group1}  !  ==&gt; Fatal error occurred, no output PDF file produced! Why is using "for...in" for array iteration a bad idea? I've been told not to use for...in with arrays in JavaScript. Why not? There seems to be a preference for to have the    18 mm - 55 mm 55 mm - 250 mm   lenses, but no mention of why they're better than a single 18-200mm. Could someone please explain why the two separate are better than the one combined, and if anyone has quantified this difference?  (I'm curious about Canon in particular.) My laptop's cable broke and sadly it seems like I need to buy a new power supply.  What I wonder is, I've found that universal power supplies are much cheaper than the official HP ones. Are they really worth it?  Another question: the original supply has these specs: 65W, 18.5V, 3.5A. However the universal supplies are more powerful (90W, 100W) and come in integer voltages (17V, 18V, 19V, etc). Are they compatible? Should I set them to 18V or 19V? Ring homomorphism and characteristic Why does change in speed of a wave make it refract? When a light wave enters a medium with a higher refractive index (e.g. from air to standard glass) and its speed decreases, why does that make it refract/bend?  I understand that wavelength decreases and frequency stays the same and therefore its speed decreases, but I can't find anywhere whatsoever why the speed decrease cause the wave to refract. So could someone please explain this? TeXnicCenter & Adobe Acrobat 10 How do you find out the caller function in JavaScript? function main() {    Hello(); }  function Hello() {   // How do you find out the caller function is 'main'? }   Is there a way to find out the call stack? How do you get vim to display wrapped lines without inserting newlines? I'm getting back in touch with my inner (g)vim due to an unscheduled MacBook mother(board) of a meltdown (my emergency backup Linux box won't run TextMate). All told I'm happy with vim's efficiency and power, but I'm mortified at how hard it is to get the kind of word wrap that even stupid HTML textareas achieve with no apparent effort.  Consider the text  Etiam ornare mollis tortor. Suspendisse sed neque. Nullam in elit. Cum sociis nullam.  By default, with an 80-character width vim displays this as  Etiam ornare mollis tortor. Suspendisse sed neque. Nullam in elit. Cum sociis nu llam.  This wrapping doesn't care about whitespace, so sometimes it just slices words into pieces (nullam in this case). Of course, you can turn on word wrap, and get this:  Etiam ornare mollis tortor. Suspendisse sed neque. Nullam in elit. Cum sociis nullam.  The problem is that vim inserts a newline at the linebreak, which I most emphatically do not want. In other words, I want the text to display exactly as vim displays it with word wrap turned on, but without inserting a newline. (This way it can be pasted into HTML textareas and email programs, among other places.)  Web searches have yielded nothing of use, despite diligent effort; I hope StackOverflow can succeed where my Google-fu has failed. Change \textwidth and \textheight in mid-document I set my \textwidth and \textheight in the preamble and would like to change both for some pages. How can this be done? E.g., the following example for \textwidth appears to work for the page number, but not for the text:  \documentclass{article}  \textwidth=5cm \textheight=5cm \begin{document} A \hfill B \eject \textwidth=10cm A \hfill B \end{document}   Output (true to scale): Book recommendation for Atomic & Molecular physics What are some interesting books for a sophomore undergrad about Atomic &amp; Molecular Physics? How to access a SQL Server database from other computer connected to the same workgroup? I have created a C# application which uses a SQL Server database. I have other computers connected to me and to each other in a workgroup. I have shared my C# application with others. When they open the application they get the error      A network related or instance-specific error occured while establishing a connection to SQL Server. the server was not found or was not accessible   But the application is working fine on my PC. The connection string I am using is   Data Source=ASHISHPC1\SQLEXPRESS;Initial Catalog=ACW;User ID=ash159;Password=ashish159   which is stored in a .config file.   The application is working fine on my PC. What must I do? I have enabled the TCP/IP in the server but the same error persists. Some change in connection string or something else? How to create a GUID / UUID I'm trying to create globally-unique identifiers in JavaScript.  I'm not sure what routines are available on all browsers, how &quot;random&quot; and seeded the built-in random number generator is, etc. The GUID / UUID should be at least 32 characters and should stay in the ASCII range to avoid trouble when passing them around.