Find a limit of a sum
$ \lim_{n \to \infty} \left(\frac 1{n^2+1}+\frac 2{n^2+2}+\frac 3{n^2+3}+\cdots +\frac n{n^2+n}\right)$
Upgrading from a modern smartphone camera without going all in on a DSLR kit What is $\int_0^1 \frac{\log \left(1-x^2\right) \sin ^{-1}(x)^2}{x^2} \, dx$? The standard files/tools that report memory seem to have different formats on different Linux distributions. For example, on Arch and Ubuntu.   Arch  $ free               total        used        free      shared  buff/cache   available Mem:        8169312     3870392     2648348       97884     1650572     4110336 Swap:      16777212      389588    16387624   $ head /proc/meminfo  MemTotal:        8169312 kB MemFree:         2625668 kB MemAvailable:    4088520 kB Buffers:          239688 kB Cached:          1224520 kB SwapCached:        17452 kB Active:          4074548 kB Inactive:        1035716 kB Active(anon):    3247948 kB Inactive(anon):   497684 kB  Ubuntu  $ free              total       used       free     shared    buffers     cached Mem:      80642828   69076080   11566748    3063796     150688   58358264 -/+ buffers/cache:   10567128   70075700 Swap:     20971516    5828472   15143044   $ head /proc/meminfo  MemTotal:       80642828 kB MemFree:        11565936 kB Buffers:          150688 kB Cached:         58358264 kB SwapCached:      2173912 kB Active:         27305364 kB Inactive:       40004480 kB Active(anon):    7584320 kB Inactive(anon):  4280400 kB Active(file):   19721044 kB    So, how can I portably (across Linux distros only) and reliably get the amount of memory—excluding swap—that is available for my software to use at a particular time? Presumably that's what's shown as "available" and "MemAvailable" in the output of free and cat /proc/meminfo in Arch but how do I get the same in Ubuntu or another distribution? Normal text is invisible when using beamer with notes and XeLaTeX I'm using beamer with xelatex to prepare a talk.  If I switch on notes on right I'm experiencing strange behaviour:  When using csqoutes in the title, all normal text afterwards becomes invisible (or white). The text selectable in the output pdf. Note that the text is also visible in the small preview on the note page.  This does not happen when using pdflatex or lualatex.  MWE:  \documentclass{beamer} \usepackage[autostyle=true,german=quotes]{csquotes}  \usepackage{pgfpages} \setbeameroption{show notes} \setbeameroption{show notes on second screen=right}  \begin{document}    \begin{frame}         \frametitle{\enquote{Enqouted Title}}     \end{frame}      \begin{frame}         \frametitle{This is the second slide}         Lorem ipsum dolor sit amet, consectetuer adipiscing elit.     \end{frame} \end{document}   Update:  csqoutes is not the culprit. Seems to be a general problem when using xelatex and beamer with notes enabled.  New MWE:  \documentclass{beamer}  \usepackage{pgfpages} \setbeameroption{show notes} \setbeameroption{show notes on second screen=right}  \begin{document}     \begin{frame}         \frametitle{First Slide Title}         Here be text     \end{frame}      \begin{frame}         \frametitle{This is the second slide}         Lorem ipsum dolor sit amet, consectetuer adipiscing elit.     \end{frame} \end{document} I've created a map system for a game that runs on the principle of drawing the picture of the map from tiles. There are many reasons for this which I won't go into here but if you really want to know then I'm sure you can find out how to contact me ;)  I have  so you can see exactly where the problem lies and the source. The issue is the line between the top 2 tiles and the bottom 2 tiles, I can't figure out why it's gone like this and any help would be appreciated.  In the source is a marker called "stackoverflow", if you search for "stackoverflow" when viewing source then it should take you to the table in question.  I have also uploaded an . Folders Completely Hidden Except via Save As I'm using an audio program called Supercollider on Windows 10. I have saved some files in a folder called "tunes" from SC via Save As, but Windows Explorer and CMD both seem unable to recognise access or recognise the "tunes" folder.  C:\Users\HP&gt;cd "C:\Program Files (x86)\SuperCollider-3.7.2\supercollider-robin\tunes" The system cannot find the path specified.  C:\Program Files (x86)\SuperCollider-3.7.2\supercollider-robin&gt;dir/a doesn't show it either.  However, when saving from SC with Save As, it's there clear as day. I can even shift+right-click to get the path: "C:\Program Files (x86)\SuperCollider-3.7.2\supercollider-robin\tunes"  This makes no sense to me. Can anyone explain and tell me how to access my folder tunes folder please? Recently I bought a new laptop that came with Windows 10 installed but not activated. I use both Windows 10 and Ubuntu 18.04, so I tried making a dual boot with a USB flash drive. It was recognized by the BIOS, I tried Try Ubuntu without installing and Install Ubuntu. With both options the PC freezes, and I need to press the power button. It's shown very fast some errors that are listed below:  [ 0.064522] ACPI Error: Method parse/execution failed \_SB.PCID.RPOB.PXSX, AE_NOT_FOUND (20170831/parse-550)  [ 0.066316] ACPI Error: [_SB.PCID.RPOB.PXSX], Namespace lookup failure, AE_NOT_FOUND (20170831/download2-191)  [ 0.066325] ACPI Error: AE_NOT_FOUND, During name lookup/catalog (20170831/psobject-252)  [ 0.246232] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246248] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246260] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246272] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246285] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246297] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246310] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)  [ 0.246322] ACPI Exception: AE_NOT_FOUND. Evaluating _PRS (20170831/pci_link-176)   I'm using NVIDIA GTX 1050 Ti graphics card and Intel i7-8750H processor.  I talked to the customer support and they just said that my laptop might not be compatible with Ubuntu. I also tried Ubuntu 16.04, but there were no changes.  EDIT: Thanks a lot for all the answers, but unfortunatelly I returned the PC to the store, neither the technical support found a solution for the problem, they just said: "Our PCs are just able to work with Windows, anyother OS might work but without our warranty". How can I create a cross product like the one in the picture.    \documentclass{article} \usepackage{tikz} \begin{document}  \begin{tikzpicture}[line width=.7pt] \draw [-&gt;] (-.2,0)node[below]{$o$}--(4.5,0)node[below]{$x$}; \draw [-&gt;] (0,-.2)--(0,2)node[left]{$y$};  \end{tikzpicture}  \end{document} Windows Batch recursive delete old files I was surprised recently to find that it's possible to have a return statement in a finally block in Java.  It seems like lots of people think it's a bad thing to do as described in ''. Scratching a little deeper, I also found '' which shows some pretty horrible examples of other types of flow control in finally blocks.  So, my question is, can anyone give me an example where a return statement (or other flow control) in a finally block produces better / more readable code? Can I cast a Warlock spell with another (higher) spell slot from a different multiclass? Reviewing an answer to a recent question I posted, I had a thought about Armor of Agathys. In the event of a Sorcerer 18 / Warlock 2 build, would the character be able to cast Armor of Agathys with a 9th level spell slot, thus getting 45 Temporary Hit Points and dealing 45 damage when hit?   Is the spell in any way limited to being cast using Warlock spell slots or to a maximum of a 5th level spell slot? In the Tiny Tina DLC "The Beard Makes the Man" quest, the objectives are (1) Crush five drunk dwarves, (2) Pick up five beards, and (3) Get five dwarves drunk. (The last one's optional.) I found the miner dwarves in the mine on the minimap, but they won't follow me into the crusher machine. How do I lure them? Does it have to do with getting them drunk, and how can I do that with no alcohol around? I thought getting drunk was optional? Charging lead-acid batteries? Per the title, does $\displaystyle\sum_{n=1}^{\infty} \sin(\pi(2+\sqrt{3})^n)$ converge? Converge absolutely?   I'm stuck on this question, not sure how to approach it.  Thank you! A question I'm struggling with is to prove or disprove that the automorphism group of a finite cyclic group must be cyclic. I think the statement is false but have not been able to come up with a counterexample.  Thank you for any assistance you can provide. Is there a good casual online place to practice/learn bridge? I know that Pogo.com (which powers Yahoo Games) has a long running online bridge game and that there are a handful of places for serious tournament/MasterPoint level bridge players online (though most seem based on software written a decade or more ago) but are there any places to play, practice and learn bridge in a more casual manner? Ideally via a well designed modern piece of software? Greatest comeback in 2nd leg match I got a integrated GD, which is Intel, and another discrete GD, AMD Radeon 6490 HD I am using ubuntu 11.10  1st, when I boot into Windows, my GD is indeed AMD Radeon 6490 HD, but when I boot into Ubuntu, it shows that I have AMD Radeon 6470 instead.  2nd, I try most methods only to install driver for my AMD/ATI graphic card. First by jockey(fail, boot with unity 2D instead) and install manually (fail, boot into blank screen).   3rd, I give up using the AMD/ATI graphic card. Then I got a new problem. Both my graphic cards are powered on on startup, which causes my laptop to over heat.   I view the content of /sys/kernel/debug/vgaswitcheroo/switch  0:DIS: :Pwr:0000:01:00.0 1:IGD:+:Pwr:0000:00:02.0   Then I switch off IGD using echo OFF &gt; /sys/kernel/debug/vgaswitcheroo/switch and I get  0:DIS: :Off:0000:01:00.0 1:IGD:+:Pwr:0000:00:02.0   But after I reboot, the discrete graphic card is powered on again. How to solve this? Can't create new folder from anywhere in Windows 7 I have this problem on two of my new laptops and can't seem to find a decent workable solution elsewhere in forum land. The problem is that on my Windows 7 Professional machines the right mouse button doesn't show the New Folder option and elsewhere as well (via Explorer) I'm unable to create new folders.   I'll be happy to get this tiny problem resolved and declare that Windows 7 is almost perfect! Thanks to all of you in advance for your contribution!  PS: None of the Vista solutions seem to work here!      Tried NewFolderFix.reg, didn't work - "Not all data was succesfully written to the registry. Some keys are open by the system or other processes."  Converted FolderFix.reg to .inf file and that worked.  Don't recall the problem appearing after an update.  MS answer to the explore process hanging (KB 972685) was to install the latest Visual C++ Update (vcredist.exe).  Nope. That didn't help either.  I haven't touched Silverlight since installation when Windows 7 hit the shelves. I tortured the RC installation before that, and never had problems there either.    UPDATE-  Logged back into Administrator account, still missing from there. Spent a bit more time looking instead of just fixing. Just yto make sure, logged back into my user account - still OK there.  Turns out the entries in HKCR\CLSID were the culprit here. Reg file wouldn't take again (as above) but inf file fixed it. This key was unable to be entered from regfile, or altered or deleted in Regedit (Permissions).   Don't quite understand why a common key in HKCR needed to be entered separately for each user.   Here is the file I used to fix it. Just copy into notepad, save as newfolderfix.inf, rt-click and select Install  ================================================================  [Version]  Signature=$Windows NT$  [DefaultInstall]  AddReg     =REGEntries.AddReg  [REGEntries.AddReg]  HKCR,"%String0%",,0x0,"CLSID_ExecuteFolder"  HKCR,"%String0%\InProcServer32",,0x0,"ExplorerFrame.dll"  HKCR,"%String0%\InProcServer32","ThreadingModel",0x0,"Apartment"   [Strings]  String0 = "CLSID\{11dbb47c-a525-400b-9e80-a54615a090c0}"  =============================================================   Thanks to others who helped point me in the right direction. I have been trying to show these two inequalities hold for all positive integers n, but I don't know how to proceed at all... I have tried playing around with them but I didn't find anything helpful. I have also tried induction but I couldn't make it work.