How do I integrate the trigonometric term ?  $$\sec^{3} \theta$$  My assumption  I tried to write it in cosine form and apply formula of $\cos^{3}\theta$ , but to no purpose. What should I do ?
I need to calculate the following indefinite integral:  $$I=\int \frac{1}{\cos^3(x)}dx$$  I know what the result is (from Mathematica):  $$I=\tanh^{-1}(\tan(x/2))+(1/2)\sec(x)\tan(x)$$  but I don't know how to integrate it myself. I have been trying some substitutions to no avail.   Equivalently, I need to know how to compute:  $$I=\int \sqrt{1+z^2}dz$$  which follows after making the change of variables $z=\tan x$.
I'm running a VPS of a german provider and want to switch from Ubuntu to CentOS. There I tried to install firewalld (was not preinstalled), but it always fails with the error  ERROR: Failed to load nf_conntrack module: modprobe: ERROR: could not find module by name='nf_conntrack' modprobe: ERROR: could not insert 'nf_conntrack': Function not implemented modprobe: ERROR: Error running install command for nf_conntrack modprobe: ERROR: could not insert 'nf_conntrack': Operation not permitted   Obviously the nf_conntrack kernel module was not found. Since this is a VPS, I cannot tinker with the kernel modules. On the support site of my provider I found a list of available kernel modules, for example:  ip_conntrack_netbios_ns ipt_conntrack    ip_conntrack    ip_conntrack_ftp    ip_conntrack_irc   Since nf_conntrack is not listed here, does that mean, that I cannot use firewalld? Is it possible to run it without this module?  I guess I could use iptables, if I wanted to (it seems to run correctly). But as I have more experience with firewalld, I would like to stick with it.    CentOS Linux release 7.7.1908 (Core)  uname -a: Linux xxxxxx.xxxxxxxx.xxx 3.10.0-042stab140.1 #1 SMP Thu Aug 15 13:32:22 MSK 2019 x86_64 x86_64 x86_64 GNU/Linux How do I submit .jar file to the ubuntu software center I am writing an app using JAVA Swing for all platforms. After that I want to add this app to Ubuntu Software Center for free Is it possible?   My app is just one *.jar file, its helping to play card games.  I dont know Python language and saying the truth - dont want to learn it now.  What should I do to be able to submit my app? Moments of the truncated normal distribution (univariate) away from the mean Cardinality and infinite sets: naturals, integers, rationals, bijections Can you take Gorrilla Glue in Hold Luggage on a plane? How do you forcefully remove apps in Windows 10? How can I remove apps that Windows doesn't seem to allow to be uninstalled, like Xbox and Groove Music? I am trying to use the Directory.GetFiles() method to retrieve a list of files of multiple types, such as mp3's and jpg's.  I have tried both of the following with no luck:  Directory.GetFiles("C:\\path", "*.mp3|*.jpg", SearchOption.AllDirectories); Directory.GetFiles("C:\\path", "*.mp3;*.jpg", SearchOption.AllDirectories);   Is there a way to do this in one call? Did Harry Potter lose Voldemort's powers when he lost his connection to Voldemort? Harry noted to Dumbledore that he had a number of things in common with Voldemort. And it was later revealed that some of Voldemort's power was transferred to Harry when Voldemort tried to kill him. So, what powers did Harry get from Voldemort (i.e. Parseltongue and others) and did they all leave him when he stopped being a horcrux?    Update In the Chamber of Secrets Dumbledore states that Harry has many qualities that Salazar Slytherin values in his hand picked students. Parseltongue - resourcefulness - determination - a certain disregard for rules.    So, does anyone know what specific powers Harry got from Voldemort and is there anyway to tell if he lost anything else besides Parseltongue? Why there's no article with 'Mexican' and 'an' with American in sentence: "She’s Mexican. But she’s married to an American."   (Pimsleur English course) I understand that when I press and release the power button on the top of my iPhone or iPad, it stays on but turns off the screen.  Whereas if I press and hold the power button, a "slide to turn off" control appears on the screen.  Sliding this, as I was told, does turn the unit off, but it does so by suspending the RAM to disk (flash memory, actually.) So, when turning on the iPhone or iPad, it isn't so much rebooting the OS as it is resuming it from flash storage.  How to force the OS to completely reboot on these devices? Understanding the difference between two theorems related to $|G\,:\,K|=|H\,:\,K|\cdot|G\,:\,H|$. I have an array of Foo objects. How do I remove the second element of the array?  I need something similar to RemoveAt() but for a regular array. Rings and some of their properties So I am studying for an exam and was wondering if anyone could explain some of the reasoning being the proofs of the following properties:   Let R be a ring with $a,b\in R$. Then    $a0=0a=0$  $a(-b)=(-a)b=-ab$ $(-a)(-b)=ab$   Proof 1:   $a0=a(0+0)=a0+a0$ hence $a0=0$   I don't really understand why $a0+a0$ proves that $a0=0$ How to draw neat polygons around scatterplot regions in ggplot2 This is a question from my proofs course review list that I have had trouble understanding.   I understand the concept of disjoint sets.  I'm not sure what they mean by countable. How would one prove a set is countable and furthermore, that the union of two countable sets is countable.  Please help me get started with the question by understanding this concept. How to speed up 4e combat I DM a group of four PC's and even "easy" battles take at least an hour to resolve. Normal encounters take even longer! I want to speed up combat so my players can do more in a session.  I've been trying a lot to speed up combat, we are already using:   Initiative cards that the players keep up 30 second bonus rule: if someone take his turn within 30 seconds, he receives a token. This token can be used to give a +1 on attack or damage, after rolling. Completely removed healing surges Checked all character sheets, they are roughly equal Roll damage and attack at the same time   I even introduced an experienced player, which helped my party to play more strategic, but speed hasn't improved.  Also the party is Lv 8, nearing Lv 9.  This is not an issue of the DM's turn taking too long. My turns take about 60 seconds tops. The 30 second rule helps a lot, most of the the players turns are within or near 30 seconds.   The major issue appears to be the sheer number of rounds, averaging on 25-30 rounds needed to resolve even a "normal" encounter.  What can I change to resolve combat faster?  I'm looking for both 4e solutions, system agnostic and home brew solutions. android - out of memory exception when creating bitmap Recover data from SD card Print box drawing characters with pdfLaTeX I need to print some unicode characters (of box drawing family) in my document. I found this  that is very similar to mine but is valid only for XeLaTeX. There is a valid way to do this with pdfLaTeX or I have to use XeLaTeX instead? My /boot partition hit 100% and now I can't upgrade. Can't remove old kernels to make room My first issue was when I tried to apt-get update or apt-get upgrade. On upgrade I get the following error:  You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies: linux-image-server : Depends: linux-image-3.2.0-27-generic but it is not installed E: Unmet dependencies. Try using -f.   I tried running apt-get install -f and this was the output(after saying yes on prompt)  (Reading database ... 186183 files and directories currently installed.) Unpacking linux-image-3.2.0-27-generic (from .../linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb) ... Done. dpkg: error processing /var/cache/apt/archives/linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb (--unpack):  failed in write on buffer copy for backend dpkg-deb during `./boot/System.map-3.2.0-27-generic': No space left on device  No apport report written because the error message indicates a disk full error                                                                           dpkg-deb:    error: subprocess paste was killed by signal (Broken pipe) Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-27-generic   /boot/vmlinuz-3.2.0-27-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic Errors were encountered while processing: /var/cache/apt/archives/linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried running apt-get autoremove and it gives me the same error as apt-get upgrade.  When I run df, I get this for /boot:  /dev/sda1                    233191     230297         0 100% /boot   So, I read elsewhere that I should try to purge old kernels. I checked for what kernels I had with:  $ dpkg -l linux-image-\* | grep ^ii ii  linux-image-2.6.38-13-server  2.6.38-13.52  Linux kernel image for version 2.6.38 on x86_64 ii  linux-image-3.0.0-13-server   3.0.0-13.22   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-14-server   3.0.0-14.23   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-15-server   3.0.0-15.26   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-16-server   3.0.0-16.29   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-17-server   3.0.0-17.30   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.2.0-24-generic  3.2.0-24.39   Linux kernel image for version 3.2.0  on 64 bit x86 SMP ii  linux-image-3.2.0-25-generic  3.2.0-25.40   Linux kernel image for version 3.2.0  on 64 bit x86 SMP ii  linux-image-3.2.0-26-generic  3.2.0-26.41   Linux kernel image for version 3.2.0  on 64 bit x86 SMP   When I try to remove the oldest with this:  $ sudo apt-get purge linux-image-2.6.38-13-server Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: linux-image-server : Depends: linux-image-3.2.0-27-generic but it is not going to be     installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   How can I free up or extend boot without messing up my installation?