Prove that the derivative of an even differentiable function is odd, and the derivative of an odd differentiable function is even.
Derivative of an even function is odd and vice versa
What is the difference between String.Empty and "" (empty string)? Why is 'that' sometimes optional before dependent clauses? Ubuntu 16.04 VIM without python support! Although Ubuntu 16.04 release notes mention that:  The default VIM package has been built against python3 instead of python2.  Yet after I installed vim with the following command:  sudo apt-get install vim   And checked:  vim --version   It showed:  -python -python3   Is it a bug? How do I get vim with Python support? When does a flying creature start and end falling? Situation:  Alice the Aarakokra sees Bob the Battlemaster coming. She ascends to 605', just out of the 600' range of Bob's longbow.  Bob (Str 14) performs a running high jump 5' into the air and successfully hits Alice with his longbow, despite firing at disadvantage for long range. He spends one of his maneuver dice to perform the Trip Attack maneuver, and succeeds on the contested roll to knock Alice prone.  Alice is now flying and prone, so she falls. Falling does 1d6 bludgeoning damage per 10' fallen, to a maximum of 20d6.  Questions:   When does Alice start falling? It is on Bob's turn as soon as she's knocked prone, or some time else such as the beginning of her own next turn? When does Alice hit the ground? On Bob's turn as soon as she's knocked prone, or some time else?   These answers determine whether anyone can save Alice from her 20d6 of certain doom.   Is a reaction (e.g. casting Feather Fall) on Bob's turn the only hope? Can Alice's ally Charlie swoop in on his subsequent turn within the same round to catch her? Can Alice spend half her movement on her next turn to "stand from prone" and pull out of her involuntary dive? If Alice had expected to be shot down, could she have spent an action to be Ready to "stand from prone" while moving through Bob's airspace? What process created the /var/lib/dpkg/lock-frontend file in Ubuntu? I have just booted my clean Ubuntu 18.04 LTS VM and tried to install some application with sudo apt install.  But got error message:     E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)       E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?   What process created the /var/lib/dpkg/lock-frontend file in Ubuntu? How to gently stop it and take manual control on APT? Clerical mistake in UK visa application: should I make a pen-and-ink correction or electronically edit the PDF? I've gone through all similar questions but I believe my specific question doesn't have an answer yet.  I've applied for a Standard Visitor visa. After I completed the application, made an appointment and paid the fee, I noticed that the way I spelled my name on the application differs from how it is spelled in the passport by 1 letter (this is partially because of myself being an idiot, but mainly because my new passport has an incorrect transliteration of my name, whereas my old passport and any other document in my life has the correct one).  So here are the options I see:   Print the application and make a pen-and-ink correction with a black ballpoint pen by crossing the printed name/letter and writing the correct one - as answers to other similar questions suggests. Edit the PDF electronically and print it so that there are no visible corrections. However, as the form is saved at their end, there will be a discrepance between the printed form and saved form with no visible signs of correction.   Which way has better chance for me to have my application accepted?  Also (probably doesn't matter much but still): if it's the pen-and-ink correction, is it better to cross-out the whole name or only the wrong letter? Can polymorph and true polymorph change a PC's race and sex? TikZ: What EXACTLY does the the |- notation for arrows do? I am currently trying to work out how the perpendicular arrows  work, and I fail.  Taking:  \draw [arrow] (node1) -- node[sloped, above] {Caption} (node1 |- node2.north west);   I suspected that the notation meant: Draw an arrow from node 1, to the north-west corner of  node 2. Make the arrow perpendicular to node 1.  Further attempts to draw arrows told me: No, that's not it. I have sadly failed to figure out what exactly the notation is supposed to be doing though! Is there any "explanation for dummies" that will lead me to understand what exactly    node1 |-   Is supposed to do?  Thanks! I have seen this many times, a question is being asked because a previous, duplicate question was asked and answered a few years ago and has no longer relevant answers.  The  is to edit the old question, or add new answers to it, but it is not always happening.  I was wondering, should I still mark it as duplicate and vote to close it? Or just leave it as is? Why does my NTFS partition mount as read only? Until recently both my Windows Partition (C:) and my Data Partition (E:) would mount as read/write. Now both seem to only mount as read-only.    GParted Resize (Error)  ntfsresize v2.0.0 (libntfs 10:0:0) Device name : /dev/sda4 NTFS volume version: 3.1 Cluster size : 4096 bytes Current volume size: 86207623680 bytes (86208 MB) Current device size: 86207627264 bytes (86208 MB) New volume size : 78662066688 bytes (78663 MB) Checking filesystem consistency ... Accounting clusters ... Space in use : 62126 MB (72.1%) Collecting resizing constraints ... Needed relocations : 1606868 (6582 MB) Schedule chkdsk for NTFS consistency check at Windows boot time ... Resetting $LogFile ... (this might take a while) Relocating needed data ... ERROR: Extended record needed (1032 &gt; 1024), not yet supported! Please try to free less space.   chkdsk Output:     Checking file system on E: The type of the file system is NTFS. Volume label is Data.  A disk check has been scheduled. Windows will now check the disk.                            99482 file records processed.   495 large file records processed.                        0 bad file records processed.                            0 EA records processed.                                  0 reparse records processed.                             104412 index entries processed.                          0 unindexed files processed.                             99482 security descriptors processed.                    2466 data files processed.                              CHKDSK is verifying Usn Journal...   4479208 USN bytes processed.                                      Usn Journal verification completed. Windows has checked the file system and found no problems.  84187132 KB total disk space.   60479688 KB in 69969 files.      15520 KB in 2467 indexes.          0 KB in bad sectors.     174336 KB in use by the system.      65536 KB occupied by the log file.   23517588 KB available on disk.       4096 bytes in each allocation unit.   21046783 total allocation units on disk.    5879397 allocation units available on disk.  Internal Info: 9a 84 01 00 00 1b 01 00 fc 1a 01 00 00 00 00 00  ................ 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................ 42 00 00 00 52 73 5c 77 b0 e7 1d 00 b0 df 1d 00  B...Rs\w........   fstab  # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # &lt;file system&gt; &lt;mount point&gt;   &lt;type&gt;  &lt;options&gt;       &lt;dump&gt;  &lt;pass&gt; proc            /proc           proc    nodev,noexec,nosuid 0       0 # / was on /dev/sda5 during installation UUID=8213cc89-2438-41b9-899f-13b4c5b299af /               ext4    errors=remount-ro 0       1 # swap was on /dev/sda6 during installation UUID=45873767-d9ae-4f0c-baab-ffc2726ac24e none            swap    sw              0       0   Checked the drive in GParted, GSmartControl and with ntfsfix, all completed successfully, no change.  Partitions  dev/sda1 NTFS WinRE dev/sda2 NTFS Windows C: dev/sda3 Extended dev/sda4 NTFS Data E: dev/sda5 EXT4 Ubuntu dev/sda6 linux-swap    I am looking for an explanation of:    Internal Info: 9a 84 01 00 00 1b 01 00 fc 1a 01 00 00 00 00 00  ................ 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................ 42 00 00 00 52 73 5c 77 b0 e7 1d 00 b0 df 1d 00  B...Rs\w........   and    Resetting $LogFile ... (this might take a while) Relocating needed data ... ERROR: Extended record needed (1032 &gt; 1024), not yet supported! Please try to free less space. What is the point of throwing candy on the ground using the "Throw 10 candies on the ground"? All that seems to happen is that the text under it becomes more and more disappointed in me. ಠ_ಠ I needed to change the SID of an Oracle XE database (not the Service Name) to match a production database.  When I tried searching online, most of the pages were describing changing or adding a service name through tnsnames.ora; that's not what I needed to do. We always change subject and verb positions in whenever we want to ask a question such as "What is your name?". But when it comes to statements like the following, which form is correct?        I don't understand what are you talking about.   I don't understand what you are talking about.      Another example        Do you know what time is it?   Do you know what time it is?      Another example        Do you care how do I feel about this?   Do you care how I feel about this? Why is it "If I were you" and not "If I was you"? What is a good use case for static import of methods? Just got a review comment that my static import of the method was not a good idea. The static import was of a method from a DA class, which has mostly static methods. So in middle of the business logic I had a da activity that apparently seemed to belong to the current class:  import static some.package.DA.*; class BusinessObject {   void someMethod() {     ....     save(this);   } }    The reviewer was not keen that I change the code and I didn't but I do kind of agree with him. One reason given for not static-importing was it was confusing where the method was defined, it wasn't in the current class and not in any superclass so it too some time to identify its definition (the web based review system does not have clickable links like IDE :-) I don't really think this matters, static-imports are still quite new and soon we will all get used to locating them.  But the other reason, the one I agree with, is that an unqualified method call seems to belong to current object and should not jump contexts. But if it really did belong, it would make sense to extend that super class.  So, when does it make sense to static import methods? When have you done it? Did/do you like the way the unqualified calls look?  EDIT: The popular opinion seems to be that static-import methods if nobody is going to confuse them as methods of the current class. For example methods from java.lang.Math and java.awt.Color. But if abs and getAlpha are not ambiguous I don't see why readEmployee is. As in lot of programming choices, I think this too is a personal preference thing.   Thanks for your response guys, I am closing the question. How can I prove that the additive group of rationals is not isomorphic to a direct product of two nontrivial groups? I am working through Paolo Aluffi's new GSM text on my own (self-study). On page 63, he asks the reader to     Prove that $\Bbb{Q}$ is not the direct product of two nontrivial groups.   For some context, this is an exercise following a section entitled "The category Grp".  I am assuming that he means "is not isomorphic to the direct product of two nontrivial groups", and I can see two possible ways to proceed with this proof, but have been unsuccessful with either approach.    Approach 1:  Show that the additive group of rationals has a property that is preserved by isomorphism that the direct product of two nontrivial groups does not have or vice-versa.  This seems challenging unless I can significantly narrow down the properties that a direct product of two nontrivial groups that was isomorphic to $\Bbb{Q}$ would necessarily have.  Approach 2:  Considering the section in which this question occurs, show that if $G$ and $H$ are nontrivial groups and $\Bbb{Q} \cong G \times H$, then there are homomorphisms $\varphi_{G}:\Bbb{Q} \rightarrow G$ and $\varphi_{H}:\Bbb{Q} \rightarrow H$ which do not factor or do not factor uniquely through the product $G \times H$.  This would be a contradiction, as $G \times H$ is a final object in the category Grp.  I would greatly appreciate suggestions on how to proceed further with either of these approaches or with alternate approaches. Remove space around tikz How can I remove ALL space around TiKZ. So given MWE below, I want no space between fbox and the node box (so essentially I want to see 1 line). How to realize this?   Is this space in tikzpicture or in \fbox?   How to remove space between \fbox and node    MWE  \documentclass{article} \usepackage{tikz}  \begin{document} \fbox{%   \begin{tikzpicture}[node distance = 0.8cm and 0.2cm]%     \node[draw] (center) {CENTER}; %   \end{tikzpicture}% } \end{document} Change the folder that Windows Explorer starts at In Windows7, when you open the Windows Explorer using the pinned Windows Explorer button on taskbar, it opens WE and points it to My Documents folder.  Is there a way to change this so it doesn't open My Documents, but rather "Computer" just as Windows+E keyboard shortcut does? Octal number literals: When? Why? Ever? I have never used octal numbers in my code nor come across any code that used it (hexadecimal and bit twiddling notwithstanding).  I started programming in C/C++ about 1994 so maybe I'm too young for this? Does older code use octal? C includes support for these by prepending a 0, but where is the code that uses these base 8 number literals? Implement multiple inheritance in Javascript