If he had known I was single, he would have asked me out.    Is this correct? In this case he had no idea I was single but he would have asked me out if he knew that. If not, how should I say that?

I know that in the following sentences "If I had known" has to be used in the place of "If I knew" to form the grammatically right sentences. What I really want be sure of is that as a native if all the 3 examples given below sound natural to you though or do you find it odd using it that way and so on? cause I've come across this to be used that way pretty often and it makes me wonder.  Please mention sequences of verb tenses in your responds too..(e.g, In the first example Subject wishes to be informed of the object's coming as s/he was on the way. looks like same time action)        If I knew you were coming, I would've arrived from work earlier    If I knew you would/were gonna come, I would've arrived from work earlier   If I knew you had come, I would've arrived from work earlier


I am trying to install an SSL certificate on my WAMP server.  W:\wamp\bin\apache\apache2.2.22\bin>echo %OPENSSL_CONF% w:\wamp\bin\apache\apache2.2.22\conf\openssl.cnf  W:\wamp\bin\apache\apache2.2.22\bin>openssl req -x509 -new -out my.root.ca.crt - keyout my.root.ca.key -days 3650 Loading 'screen' into random state - done Generating a 1024 bit RSA private key ....++++++ ........++++++ writing new private key to 'my.root.ca.key' Enter PEM pass phrase:   Enter PEM pass phrase is where I am stuck.  It won't let me type anything.  And also, am I supposed to come up with my own pass phrase and tell this program to use that, or am I supposed to have a pre-determined pass phrase set by... well... apache, openssl, wamp, etc.

This is a  about  the use of a *AMPP's stack.    I recently had a talk with some experienced people and they suggested to me not to use a WAMP stack, and instead install apache, mysql and php separately.  I don't understand why they have suggested this, though, so can anyone tell me?  Is there a particular disadvantage of WAMP, or a particular advantage to installing all of them separately?  Since a WAMP stack itself is composed of apache, mysql and php, then what's the difference between using the WAMP stack and installing them all separately?


I am testing for a given post request field on a script that can be called either from the command line, or over HTTP as a GET or POST request. As such, $_POST can be undefined. Is there a simple way of rewriting this statement?  if (isset($_POST) && isset($_POST['function']) && $_POST['function'] == "login"):   I could suppress errors with the @-operator — is that bad practice?  if (@$_POST['function'] == "login"):   I could use PHP 7.0's null coalesce operator, but that introduces a useless literal purely designed to throw a false:  if (($_POST['function'] ?? null) == "login"):

I have a PHP script that needs to determine if it's been executed via the command-line or via HTTP, primarily for output-formatting purposes. What's the canonical way of doing this? I had thought it was to inspect SERVER['argc'], but it turns out this is populated, even when using the 'Apache 2.0 Handler' server API.


Is there any way to sync iphone in ubuntu 16.04 LTS.  Please help!

What ubuntu applications provide support? (guides, how to's, status) Also, specifically, details on support for syncing music to iPhone's and iPod's with the latest OS version:   Can you sync music to apple devices using >iOS4? (iPhone & iPod) What applications allow you to do this and how? (guides, how to's, status)    What has already been established is:   Apple does not support Linux and has no plans to.  provides some support, however it currently does not support music/video synchronization with devices >iOS4. Go to  and scroll to the section titled "" to see if your device version is supported.


The hypotenuse of any Pythagorean triple seems not to be divided by some primes such as $3, 7$. What are the others? Are there infinitely many such primes?  In other words, I am looking for number $c$ such that $a^2 + b^2 = kc$  have no integer solutions for any positive integer $k$ and $a,b < c$.

As the title implies.  I'm proving it by contradiction and I've already ruled out $p \equiv 0$ and $2$ (mod $4$).  I'm having trouble proving that it cannot be $\equiv 3$ (mod $4$). Namely, if $p \equiv 3$ (mod 4), then $m^2 + n^2 \equiv 1$ or $3$ (mod $4$). I know that $m^2 + n^2$ cannot be congruent to $3$ (mod $4$); but what about $1$?  Thank you.


I need to prove the following, Suppose $G$ is an Abelian group. Show that $H = \{g ∈ G : |g|\ \hbox{is finite}\}$ is a subgroup. I know that to prove a subset is a subgroup one can prove $ab^{-1} \in H$ for all $a,b \in H$ but I'm not sure how to apply that for this problem.

I need to show that elements of finite order in an abelian group form a subgroup of that group. Where do i start ?


My question is: given an abelian group $G$ with addition $+$, is there some natural multiplicative structure that arises so that we can define a ring $(G, +, \cdot)$. For instance, multiplication on $\mathbb{Z}$ and $\mathbb{Z}_n$ are entirely determined by addition, since it must be that $ma = a + \ldots + a$, where the addition is $m$ times.  For finitely generated abelian groups $G$, we know that its representation according to the Fundamental Theorem of Finitely Generated Abelian Groups is  $$G = \mathbb{Z}_{p_1^{r_1}} \times \ldots \times \mathbb{Z}_{p_n^{r_n}} \times \mathbb{Z} \times \ldots \times \mathbb{Z}$$  Since each of those factors has a natural ring structure, we can define a ring structure on $G$ as the product of these ring structures. That leaves the question: can we define a "natural" ring structure on infinitely generated abelian groups $G$?

Given some Abelian group $(G, +)$, does there always exist a binary operation $*$ such that $(G, +, *)$ is a ring? That is, $*$ is associative and distributive:  \begin{align*} &a * (b * c) = (a*b) * c \\ &a * (b + c) = a * b + a * c \\ &(a + b) * c = a * c + b * c \\ \end{align*}  We also might have multiplicative identity $1 \in G$, with $a * 1 = 1 * a = a$ for any $a \in G$. Multiplication may or may not be commutative.  Depending on the definition, the answer could be no in the case of the group with one element: then $1 = 0$. But the trivial ring is not a very interesting case. For cyclic groups the statement is certainly true, since $(\mathbb{Z}_n, +, \cdot)$ and $(\mathbb{Z}, +, \cdot)$ are both rings. What about in general? Is there some procedure to give arbitrary abelian groups ring structure?


In C++ I could use pointer arithmetic to grab everything from a start position to the end of an array. What do you do in C# to accomplish the same thing?  using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;  namespace ConsoleApp1 {     class Program     {         static string GetText(byte[] value, uint startPos)         {             // TODO - What goes here?             return "";         }          static void Main(string[] args)         {             byte[] value = new byte[] { 0x41, 0x42, 0x42, 0x42 };             string result = GetText(value, 1);             Console.WriteLine(result);         }     } }   Expecting output: BBB

How do you do it? Given a byte array:  byte[] foo = new byte[4096];   How would I get the first x bytes of the array as a separate array? (Specifically, I need it as an IEnumerable<byte>)  This is for working with Sockets. I figure the easiest way would be array slicing, similar to Perls syntax:  @bar = @foo[0..40];   Which would return the first 41 elements into the @bar array. Is there something in C# that I'm just missing, or is there some other thing I should be doing?  LINQ is an option for me (.NET 3.5), if that helps any.


I have dual booted with Windows, I have allocated Windows for 180GB and For Ubuntu 46GB. Recently I wanted to increase Linux root partition hard drive space and I shrink from windows and unallocated space created.     Now I cannot shrink it to boot partition of Linux, Whenever I tried to click resize/move on /dev/nvme0n1p4 it simply says there is no unallocated space to add.    I tried Gparted live boot also, I get the same response. Now I want to merge all the unallocated to space to my Linux root partition(/dev/nvme0n1p4) how to do it?  And Why am I having 3 separate unallocated space? Can I not merge them to single?  root@tom-linux:/home/tom# resize2fs /dev/nvme0n1p4 resize2fs 1.43.4 (31-Jan-2017) The filesystem is already 12207104 (4k) blocks long.  Nothing to do!

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


For a periodic function we have: $$\int_{b}^{b+a}f(t)dt = \int_{b}^{na}f(t)dt+\int_{na}^{b+a}f(t)dt = \int_{b+a}^{(n+1)a}f(t)dt+\int_{an}^{b+a}f(t)dt = \int_{na}^{(n+1)a}f(t)dt = \int_{0}^{a}f(t)dt.$$ , but I don't understand how we obtain $\int _{b+a}^{\left(n+1\right)a}\:f\left(t\right)\:dt=\int _b^{na}\:f\left(t\right)dt$ in our equality?

I want to prove:     For an integrable function $f(x)$ and periodic with period $T$, for every $a \in \mathbb{R}$, $$\int_{0}^{T}f(x)\;dx=\int_{a}^{a+T}f(x)\;dx.$$   I tried to change the values and define $y=a+x$ so that $dy=dx$ and the limits of the integrals are as we want, but I'm not sure how to use the fact that $f(x)$ is periodic.  Thanks a lot!


I have a system whose entropy is specified by three variables: Salinity $S$, pressure$p$, and density$\rho$. I have the following partial derivative: \begin{equation}   (\frac{\partial\eta}{\partial p})_{\rho,S}= -(\frac{\partial\eta}{\partial \rho})_{p,S}(\frac{\partial\rho}{\partial p})_{n,S} \end{equation} Where $\eta$ is the specific entropy: My question is where does the minus sign come from? I though it just was a chain rule but I can not explain this sign. Thanks

I can't understand why $\left(\frac{\partial P}{\partial V} \right)_T=-\left(\frac{\partial P}{\partial T} \right)_V\left(\frac{\partial T}{\partial V}\right)_P$. Why does the negative sign arise? I can easily write $\left(\frac{\partial P}{\partial V}\right)_T=\left(\frac{\partial P}{\partial T}\right)_V\left(\frac{\partial T}{\partial V}\right)_P$ from the rule of partial derivative, but what's the negative sign for?


In Unity's Launcher, if you right clicked in Nautilus you'd get shortcuts to "Personal Folder", "Documents", "Downloads", "Images, "Musics" and "Videos".     It's a feature I miss a lot since Ubuntu switched to GNOME shell, 'cause before I could go to the folder I wanted directly from the dock. Is it possible to add these shortcuts back to Nautilus icon in Ubuntu 18.04's dock?

I miss those pins I make in Windows.     How can I do the same in Ubuntu 17.10 with GNOME 3?


When I navigate to /?q=admin/structure/types/add in order to add a content type, I get a white screen of death. I'm running Drupal version 7.41 on Windows 2008 r2. Can someone walk me through the steps on diagnosing this problem? Most of the documentation I've found is written for the Linux platform, so it's not very helpful. Thanks.

I have a issue with my Drupal installation, for example:   when I enable or disable the modules, It redirects me to a blank page, when I create a new content type and save it, redirects me to a blank page, when I add a new view and save it, it redirects me to a blank page, when I try to clear the cache, it redirects me back to a blank page, or in similar cases.   Basically all the confirmation pages redirect me to a white screen. When I refresh it again, it shows me the page. I tried to increase the PHP memory value but it doesn't help.  Are there any other solutions for this?  The error which I'm having:      Fatal error: Allowed memory size of 100663296 bytes exhausted (tried to allocate 8192 bytes) in sites/all/modules/views/plugins/views_plugin_localization_none.inc on line 1


Prove that $$ N = \frac{5^{125} - 1}{5^{25} - 1} $$ is a composite number.   I just proved it will be a natural number with  quotient= $5^{100} +5^{75}+5^{50}+5^{25}+1$  But I do not know how to factorise it for proving it composite.

Prove that $n=\dfrac{5^{125}-1}{5^{25}-1}$ is a composite number   My attempt,  Let $x=5^{25}$, so that $5^{125}-1=x^5-1=(x-1)(x^4+x^3+x^2+x+1)$  $=(x^4+9x^2+1+6x^3+6x+2x^2-5x^3-10x^2-5x)(x-1)$  $=((x^2+3x+1)^2-5x(x+1)^2)(x-1)$  I'm stuck at this point and don't know how to continue anymore. Hope someone can provide a detailed solution. Thanks a lot.


I want to trace my family but am limited on funds.   What is the best way to trace my lineage online?

I'm an absolute starter to genealogy and I've always found it very interesting so last week I decided to build my family tree.  What are the key things I should consider when getting started?


The problem is to express the number  $$1\over x^5 + 2x^4 + 3x^3 + 3x^2 + 2$$  using only rational numbers in the denominator, knowing that $x^5 + 2 = -2(x + 1)(x^3 + x^2 + x)$.  (This is an example from a final exam of an algebra course from the past year (which is freely available to students).)  I know how to solve this problem, but I do not understand why this is possible. The trick comes from knowing that this number can be expressed using addition and multiplication of $x$ and rational numbers, ie. as  $$r_0 + r_1x + r_2x^2 + r_3x^3 + r_4x^4 + r_5x^5 + \dots$$  My solution follows, skip to questions if you are not interested.  From the polynomial equation it follows that $x^5$ equals $-2 - 2x - 4x^2 - 4x^3 - 2x^4$, therefore an expression containing $x$ with exponent 5 or greater can be rewritten as an expression with only $x^0$ to $x^4$.  So my number can be expressed as  $$ax^4 + bx^3 + cx^2 + dx + e$$  Putting an equals sign between these two expressions and multiplying by the denominator gives  $$1 = (x^5 + 2x^4 + 3x^3 + 3x^2 + 2)(ax^4 + bx^3 + cx^2 + dx + e)$$  I can multiply the right hand side and "normalize" it (by replacing $x^{\ge5}$) to get  $$1 = (e - f)x^4 + \dots + (2e - 2d)$$  From this formula I can create a system of linear equations, because the coefficient of $x^n$ has to be one if n equals zero, and zero otherwise. Solving this system will let me find the values of the coefficients.  Question 0: Why does this problem even have a solution of the form I used?  Question 1: Is there a solution like this for any expression $1 \over f(x)$, where f is a polynomial of $x$, knowing $x$ is a root of another polynomial? Will my method always work? Why?  Apologies if this is a duplicate, but everything I could find about rationalizing the denominator was about simple fractions like $1 \over 2 + \sqrt 6$.  I'd appreciate even just comments directing me towards what I can study because I am out of keywords.

This is an exercise in some textbooks.     Let $E$ be an algebraic extension of $F$. Suppose $R$ is ring that contains $F$ and is contained in $E$. Prove that $R$ is a field.   The trouble is really with the inverse of $r$, where $r\in R$. How to prove that $r^{-1}\in R$, in apparent lack of a characterization of $R$.  It occurred to me to use the smallest field containing $R$ ($R$ is easily shown to be an integral domain), that's the field of quotients, and proving that it's $R$ itself, but I don't really know how to proceed.  A not-too-weak, not-too-strong hint will be much appreciated.   Beware $ $ Readers seeking only hints should  beware that there is now a complete answer.


The nuclei of atoms are composed of protons and neutrons. The proton has a positive charge, and the neutron a neutral charge. Shells of electrons outside the nucleus in the atom orbit around the nucleus. Here is my question: If the protons in the nucleus possess a rival charge to the electron, why doesn’t the electron become attracted to the proton(s) in the nucleus and hence fall “into” the atom?

I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.   In particular,    I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay?  I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds.     I understand that certain aspects of quantum mechanics  to address these problems, and that there are  of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it.


My laptop has a built-in SD Card reader but it cannot detect one when inserted. Here is the result when I type lspci from the terminal:  00:00.0 Host bridge: ATI Technologies Inc RS480 Host Bridge (rev 10) 00:01.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge 00:06.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge 00:07.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge 00:12.0 IDE interface: ATI Technologies Inc IXP SB400 Serial ATA Controller (rev 80) 00:13.0 USB Controller: ATI Technologies Inc IXP SB400 USB Host Controller (rev 80) 00:13.1 USB Controller: ATI Technologies Inc IXP SB400 USB Host Controller (rev 80) 00:13.2 USB Controller: ATI Technologies Inc IXP SB400 USB2 Host Controller (rev 80) 00:14.0 SMBus: ATI Technologies Inc IXP SB400 SMBus Controller (rev 83) 00:14.1 IDE interface: ATI Technologies Inc IXP SB400 IDE Controller (rev 80) 00:14.2 Audio device: ATI Technologies Inc IXP SB4x0 High Definition Audio Controller (rev 01) 00:14.3 ISA bridge: ATI Technologies Inc IXP SB400 PCI-ISA Bridge (rev 80) 00:14.4 PCI bridge: ATI Technologies Inc IXP SB400 PCI-PCI Bridge (rev 80) 00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration 00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map 00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control 01:05.0 VGA compatible controller: ATI Technologies Inc RS482 [Radeon Xpress 200M] 04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01) 05:04.0 FireWire (IEEE 1394): O2 Micro, Inc. Firewire (IEEE 1394) (rev 02) 05:04.2 SD Host controller: O2 Micro, Inc. Integrated MMC/SD Controller (rev 01) 05:04.3 Mass storage controller: O2 Micro, Inc. Integrated MS/xD Controller (rev 01) 05:09.0 Network controller: Ralink corp. RT2561/RT61 rev B 802.11g

I have a MicroSD card in a USB adapter (which plugs into a USB port on my machine, and acts like a USB flash drive). I was using Unetbootin to make this a bootable USB flash drive with Kubuntu. But I needed to cancel while it was working. So I killed the Unetbootin process from the console.  Since then, I can't format the MicroSD or delete the folder that Kubuntu made. I have also tried mkdosfs, with no success. I can't mount the drive anymore either? What can I do to make this drive usable again?  Trying to create a new partition table in GParted, as described in Eliah Kagan's answer, does not work. It fails with the error message "imposible crear tabla de particiones" ("unable to create a partition table").


I tried the steps here for a 4312:   Both of these:  sudo modprobe -r b43 ssb wl sudo modprobe wl   return:  FATAL: Module wl not found. FATAL: Error running install command for wl (this one is only for the second one actually)   I tried the broadcom-sta, didn't work. What's confusing is down below in the next steps for STA with internet access it says to use the bcmwl one. So I install that and it succeeds but with some errors:  sudo apt-get install bcmwl-kernel-source  Reading package lists... Done Building dependency tree        Reading state information... Done The following package was automatically installed and is no longer required:   module-assistant Use 'apt-get autoremove' to remove it. The following NEW packages will be installed:   bcmwl-kernel-source 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 0 B/1,181 kB of archives. After this operation, 3,609 kB of additional disk space will be used. Selecting previously unselected package bcmwl-kernel-source. (Reading database ... 168005 files and directories currently installed.) Unpacking bcmwl-kernel-source (from .../bcmwl-kernel-source_5.100.82.112+bdcom-0ubuntu3_amd64.deb) ... Setting up bcmwl-kernel-source (5.100.82.112+bdcom-0ubuntu3) ... Loading new bcmwl-5.100.82.112+bdcom DKMS files... Building only for 3.5.0-21-generic Building for architecture x86_64 Module build for the currently running kernel was skipped since the kernel source for this kernel does not seem to be installed. ERROR: Module b43 does not exist in /proc/modules ERROR: Module b43legacy does not exist in /proc/modules ERROR: Module ssb does not exist in /proc/modules ERROR: Module bcm43xx does not exist in /proc/modules ERROR: Module brcm80211 does not exist in /proc/modules ERROR: Module brcmfmac does not exist in /proc/modules ERROR: Module brcmsmac does not exist in /proc/modules ERROR: Module bcma does not exist in /proc/modules FATAL: Module wl not found. FATAL: Error running install command for wl update-initramfs: deferring update (trigger activated) Processing triggers for initramfs-tools ... update-initramfs: Generating /boot/initrd.img-3.5.0-21-generic jtaylor991@jtaylor991-whiteHP:~$ sudo modprobe wl FATAL: Module wl not found. FATAL: Error running install command for wl   Then I do the modprobe wl commands listed above and it gives the above listed errors. It didn't work with the broadcom-sta driver either. I installed the b43 ones but nothing happened, and I don't know why so those are still installed. firmware-b43legacy-installer, b43-fwcutter and firmware-b43-lpphy-installer (yes it is a LP-PHY) are currently installed.  If I go into System Settings > Software Sources > Additional Drivers it says "Using Broadcom 802.11 Linux STA wireless driver source from bcmwl-kernel-source (proprietary) But bcmwl-kernel-source isn't installed. I could try again but I remember rebooting and it still said this.  What's funny is it found wireless networks during the Ubuntu setup/installation, I don't remember if I got it to connect or not though. I think it kept asking for a password when I put it in (yes it was right I showed password and looked at it) so I just ignored it. But right now the Enable Wireless option in the top right is just gone, it's just Enable Networking and I'm on ethernet on this HP Pavilion dv4-1435dx right here.  If I run rfkill list it shows:  0: hp-wifi: Wireless LAN     Soft blocked: no     Hard blocked: no   It was hard blocked at the beginning but unblocking it makes no change. Also it's a touch sensitive button, and it appears to be always orange no matter if it's enabled or not because when I touch it the hard blocked changes between yes and no in rfkill list. I think it was blue for a minute at one point.  What is going on?!?! Help me! Lol, thanks for any and all of your time guys. Oh yeah this is Ubuntu 12.10 fresh install.

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


I just started using LaTeX to write my bachelor thesis and everything is already set up and working (took 2 weeks but it is finally done). I was just starting to write a chapter and am wondering what would be the best or recommended way to actually write?   I am using TeXstudio and I like to use the enter key to sort my text into parts, not section or similar. Just for "visual".  And I also prefer to use double enter key to make a break.  As a result my text is not all on one single line, for example at the moment line 13 contains my whole chapter 1.   But now I read that one should prefer to use \\ or \newline instead of enter. Doing so would hinder my need for a "visual separation".   As you may have guessed I come from a word background so that is probably my problem here.  I would like to know what is the preferred way to write in this case? Kill my habits from word and just deal with huge oneliner? double enter key? \\? \newline?

What is the difference between \par, \newline, \\ and blank lines? When should I use which one?


Updater keep saying:   Failed to download repository information. Check your Internet connection.   Details:  W:Failed to fetch http://ppa.launchpad.net/screenlets/ppa/ubuntu/dists/quantal/main/source/Sources  404  Not Found, W:Failed to fetch http://ppa.launchpad.net/screenlets/ppa/ubuntu/dists/quantal/main/binary-amd64/Packages  404  Not Found, W:Failed to fetch http://ppa.launchpad.net/screenlets/ppa/ubuntu/dists/quantal/main/binary-i386/Packages  404  Not Found, E:Some index files failed to download. They have been ignored, or old ones used instead.

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?


In one question I found that when water was heated from 0°C to 15°C then the volume 1st decreases and then increases why is that so ?

How can the Anomalous Expansion of Water from 4$^\circ$C to 0$^\circ$C be explained with reference to subatomic particles?


Are there any howto guides that show the basic aspects of using SO? It would be nice to have something to link to when telling a user to stop   whenever their  is closed as "not a real question", and to edit the original one instead.  There are other simple howtos that could be useful, such as:   Tagging as homework, and giving efforts so far How not to use a title "CODE PLS!!!!!" Asking on an alternative SE site Commenting instead of posting a new answer Accepting an answer   Even something as simple as a standard screenshot with the various componented (link / button / text boxes) numbered could be extremely useful.  Related to this, what about completely new users who don't see the notifications of new comments? Perhaps it could be possible for a mod to trigger a template email to them?

UPDATE: This is now live on all Stack Exchange sites. You can access it at /help or by clicking the "help" link in the top nav or footer of any page.   We can all agree that Stack Exchange is a complicated beast that takes a while to understand. New users can be overwhelmed and confused by all of the rules, where to find them, and how to abide by them. Even though many established users leave comments linking to helpful resources, or answer questions posted to metas, it's a scattershot way to help users learn our rules and answer their questions.  And so, we're introducing a new Help Center, which you can now see here on MSO: .  Here's what we're hoping to achieve:   Consolidate important information that is currently scattered throughout a great many resources: MSO and child metas'  lists, each site's official FAQ page, blog posts, and miscellaneous other resources like our  pages and  /  guides. Any rules or explanations of basic site mechanics should be easily accessible in one place. Allow easy linking and easy navigation. Each topic is separated out onto its own page, with a unique URL to allow pointed linking to that page. Each article page also has sidebar navigation that shows other topics in the same category, as well as a list of other categories, for the rare user who is motivated to read more. Use comprehensible language that non-power users will be able to understand. A lot of our guidance, written by the community and by Stack Exchange itself, uses jargon that can be unclear to users learning our system for the first time. We want to make sure terminology is sufficiently explained and use plain language wherever possible.   This Help Center will (once we roll it out to all sites) replace the current FAQ pages. Each site will continue to have its own  tag on meta, but any policy that is essential to the functioning of the community will be rolled into the appropriate section of the new Help Center.  What's broken, and what are we missing?  We're already planning to add more features and articles to the Help Center in the coming weeks, but we wanted to show you all the core of it and get your feedback. There are additional articles that we plan to include here (especially in the "Reputation & Privileges" category), but the articles currently included should cover everything that exists in the current FAQ and old /help page /contact page (which will be redesigned when the new Help Center is live everywhere).  This is live only on MSO right now. We want to get your opinions about the Help Center in general, fix any bugs or typos you might find, and add any crucial information that's missing. Once we've addressed all those things, the new Help Center will roll out network-wide.   A couple of implementation notes:   We will be adding a "search" feature to the /help landing page that will make it easier for users with a specific problem to find the relevant article(s). Site moderators will be able to edit the  page to include lists of what is on- and off-topic for each site, just as they can currently edit the "What can I ask here?" part of the current FAQ. You may notice that some article titles are preceded by a round bullet. The bullet is temporary while Jin designs an icon, but those articles are "featured" articles; they are meant to draw attention to the most important site policies or most frequently encountered issues. Fixed   So there you have it. A new, consolidated, Help Center to provide a single resource for users looking to understand how our network works.  We're still making some small changes to this feature. Please continue to post here on meta if you encounter any bugs / typos / broken links. If you want to suggest a new page, have an issue specific to one site, or have another major change, you can start a new meta post and tag it .


I have asked several questions and received satisfactory answers. Is there a way to close out a question or does its status just stay open?

What does it mean to accept an answer? How do I accept an answer, and what are the rules? Can I accept my own self-answer? What are the reputation benefits? Which answer should I accept? Should I upvote the accepted answer? What should I do if none of the answers are suitable?      For more information, see "" in the .


If a possessive noun, which is plural, is preceded by "each", then should it use the singular or plural possessive form?  For example, which of the following is correct?    spend time in each other's presence spend time in each others' presence

Which of the following is correct?        Each person's car has four wheels.   Each persons' car has four wheels.


so for any Matrix above $R$ I'd like to prove this equation. So far I've been able to prove $\operatorname{Im}(A) \subset  Ker(A^T)^\perp$ however I can't figure how I can prove the other way around.  All help is highly appreciated.

How can I prove that, if $V$ is a finite-dimensional vector space with inner product and $T$ a linear operator in $V$, then the range of $T^*$ is the orthogonal complement of the null space of $T$?  I know what I must do (for a $v$ in the range of $T^*$, I have to show that $v\perp w$ for every $w$ in $\ker(T)$ and then do the opposite), but I don't know how to show that this inner product is zero.


Till yesterday my Ubuntu 16.04 was working fine. Today when I started my PC it showed this  The system is running in low-graphics mode your screen,graphics card, and input devices settings could not be detected correctly. You will need to configure these yourself.  After that I had to reinstall Ubuntu. I was having wifi problem earlier. Enable wifi icon was not showing in the menu. After that I tried running these commands which worked well in the first attempt  sudo apt update  sudo apt install build-essential dkms git git clone https://github.com/jeremyb31/rtl8723de.git sudo dkms add ./rtl8723de sudo dkms build rtl8723de/5.1.1.8_21285.20171026_COEX20170111-1414 sudo dkms install rtl8723de/5.1.1.8_21285.20171026_COEX20170111-1414   I again ran these commands but last 2 commands are giving me this error Kernel preparation unnecessary for this kernel.  Skipping...  Building module: cleaning build area.... 'make' all KVER=4.10.0-28-generic.....(bad exit status: 2) ERROR (dkms apport): binary package for rtl8723de: 5.1.1.8_21285.20171026_COEX20170111-1414 not found Error! Bad return status for module build on kernel: 4.10.0-28-generic (x86_64) Consult /var/lib/dkms/rtl8723de/5.1.1.8_21285.20171026_COEX20170111-1414/build/make.log for more information.   If I am able to run these two commands then definitely wifi will get working but how to solve this problem?

How do I install Wi-Fi drivers for Realtek RTL8723DE device in Ubuntu 16.04?  lspci -v | grep -i network 02:00.0 Network controller: Realtek Semiconductor Co., Ltd. Device d723


I'm new in c# and can't find the solution.  I adding two car in an array.  I want to find the biggist car length in Greateslength().   Only I can't select Carlength or others at <--------- CAN'T SELECT  How can I select:   Carlength  Widthcar  CarInfo  CarBrand   in the Greateslength()method.      abstract class Car     {         abstract int Getperimeter();     }      class Cars     {         public Car[] _Items = new Car[0];         public int Count { get; set; }          public void Add(Car car)         {             Count = Count + 1;             Array.Resize(ref _Items, Count);             _Items[Count - 1] = car;         }          public void Greateslength()         {             foreach (Car element in _Items)             {                 int largestCarLength = 0;                  if (element. > largestCarLength) <--------- CAN'T SELECT Carlength                  {                     largestCarLength = element.; < ---------CAN'T SELECT Carlength                      Console.WriteLine(element.); < ---------CAN'T SELECT Carlength                                                   < ---------CAN'T SELECT Widthcar                                                   < ---------CAN'T SELECT CarInfo                                                   < ---------CAN'T SELECT CarBrand                  }             }         }     }      class VW : Car     {         public VW(int carlength, int widthcar, string carInfo)         {             this.Carlength = carlength;             this.Widthcar = widthcar;             this.CarInfo = carInfo;             this.CarBrand = "VW";         }          private double Carlength { get; set; }         private double Widthcar { get; set; }         private string CarInfo { get; set; }         private string CarBrand { get; set; }          public override double Getperimeter()         {             return Carlength * Widthcar;         }       static void Main(string[] args)     {         VW vw1 = new VW(10, 20, "car 1");         VW vw2 = new VW(22, 11, "car 2");          Cars c1 = new Cars();         c1.Add(vw1);         c1.Add(vw2);          Console.WriteLine("--------------------");         c1.Greateslength();     }

In C#, what is the best way to access a property of the derived class when the generic list contains just the base class.  public class ClassA : BaseClass {    public object PropertyA { get; set; } }  public class ClassB: BaseClass {     public object PropertyB { get; set; } }  public class BaseClass { }  public void Main {     List<BaseClass> MyList = new List<BaseClass>();     ClassA a = new ClassA();     ClassB b = new ClassB();      MyList.Add(a);     MyList.Add(b);      for(int i = 0; i < MyList.Count; i++)     {         //I would like to access PropertyA abd PropertyB from the derived classes             } }


I know how incredibly stupid this question sounds, and I know any 2 triangles you draw with same line lengths will have the same 3 angles, but I just can't figure out the exact reason why having 3 lines of the same, or congruent, lengths, would lead to 2 triangles having the same angles. Can someone please explain?

I'm hoping that someone can provide a method for deducing the commonly known SSS congruence postulate? The postulate states     If the three sides of one triangle are pair-wise congruent to the three sides of another triangle, then the two triangles must be congruent.   I am a middle school math teacher (teaching a HS Geometry course) and would like to be able to explain/justify the triangle congruence theorems that I expect students to apply with more clarity. I understand that the Law of Cosines could be used to justify the SSS triangle congruence theorem but I wonder if a proof can use more basic properties. My students are currently learning the congruence theorems and using constructions to justify their validity. I know two ways to demonstrate the validity of SSS congruence: constructions and the Law of Cosines. Is there another way?  I've researched this and have not seen another answer so far. The Law of Cosines is the accepted answer to . I've also seen a few other questions hinting at this without a clear answer, see: . Another question on math.SE asks what I'm asking (how can we derive the triangle congruence postulates from basic axioms?)  and the accepted answer suggests only a quick visit to  but does not discuss whether or not the triangle congruence axioms follow from the basic axioms or are independent of them.


What is the name of this kids’ show from the late 80s? It was based in space, and I think it was some sort of live-action TV show. Some of the images looked like TV static, and you could buy some toy spaceships shaped like a gun to shoot at the images (and somehow get hit) to gain or lose points.  I thought it was called "Captain Skyhawk", but apparently that's an old NES game.  Does anyone know what this show was called?

I'm looking for the name of a sci-fi series, intended for children. Robots have control over the humans. There is a squad of humans who attack them. Every member in this squad has a badge on their suit, and when they touch this badge the suit becomes armed. This series was not cartoon series, it was performed by real people. The main robot character is very similar in style to Darth Vader in Star Wars. The series aired in the 1990s. I am sorry but I can't recall many details.


Is a transit visa required when travelling from Abuja to the US via the UK and Toronto on Air Canada? I will have a 12-hour layover in the UK and 6 hours in Toronto.

I'm passing through Canada, on my way to somewhere else. I'm staying only a short time.   Is there a website, or some other way of find out out if I need a visa?


In Settings -> Software & Updates -> Additional Drivers tab this window appears (for me):    I have no idea what second driver name: Unknown:Unknown is. The option to use Intel microcode for Intel CPU was intriguing so I picked it and rebooted.  Looking at my Conky monitor:    I think the system is running cooler, CPU percentage and average load factor are a little bit lower.  Other than the fact Ubuntu developers can't vet the source code, are there any pitfalls with using Intel Microcode? Does anyone know how to find out what the "unknown device" is? ie CPU, Integrated Graphics GPU, Wifi card, USB controller, Memory Bus, etc. Could it be Ubuntu doesn't know specific details about my system and I can add it to a file?  Edit 1  @karel pointed out links to duplicate questions about Intel Proprietary Microcode however, none of them ask about the title of "Unknown:Unknown". It would be nice, for me at least, to change this to something more meaningful.  Edit 2  @Pilot6 pointed out this is not a "Driver" but rather "CPU Firmware". I have changed the word "driver" to "title" in Edit 1. Also in comments below; in order to change the title "Unknown:Unknown" requires downloading source code, modifying it and recompiling.

I have recently noticed that there is an additional driver called Unknown: Unknown here which was not there before:    I have already read , and understand why it is there, but my question is, should I activate it? Will this make a difference? Or should I just leave it as it is as it sounds rather useful?    OS Information:  Description:    Ubuntu 15.04 Release:    15.04


There's one in the cage in your house, and another by the Fast Travel Station. How do you get to these boxes?  I just want to get the stuff inside so I'm have a better arsenal and stop dying as much

In the house with Tannis and the Safe in Sanctuary (the Crimson Raider hideout) there's a red Dahl branded chest behind a gate. There's a green-lit switch to the left of the door but pulling it doesn't work. Later on in the story the switch turns red and won't turn, I still can't get into the gate.  How do I open the gate and get to that chest?


I am using MySQL Workbench, my database is set to UTF-8 ("utf8 - utf8_unicode_ci"), inside it characters display correctly, so does the website (i use this tag; <meta charset="UTF-8"> ) displays them correctly. When I hardcode it to the HTML or when I echo it in php there is no issue.   When I query it in the database the special characters appear differently. For example, Workbench shows "geçmiş" and query that I send with mysqli returns "ge�mi?" on the page.  mysqli_set_charset($link, 'utf8mb4'); solved my problem.

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I have submitted a journal paper to a journal four days ago and today I received an email informing me that it has been rejected. The only reason for this is: "About 70 % of the article is similar to other documents". I know my paper and I know that I haven't copied it from anywhere else. There is a conference version of the paper, but it is different, plus it is 6 pages long, while the journal is 15 pages long, so since 6/15 = 40%, it doesn't add up to 70%, and this is not the reason for rejection. The real reason is that my PhD thesis is available online (it is mandatory at my university to add it to an open repository if I want to graduate). I graduated 3 months ago, and in fact the last chapter of my thesis consists in the paper that was rejected now. However, I was always told both by my supervisor who is a full professor with 25 years of experience (and Associate Editor of top-notch journals) and by many other people that it is not a problem to submit a paper based on an already published PhD thesis, as journals should not consider the thesis as a paper. Therefore, I am very surprised by the decision made by the editor. What should one do? Wait to graduate until the paper is accepted? That is simply ridiculous. Has this occurred to any of you? Do you know how journals behave in this case? I once reviewed a journal paper which was literally copy-pasted from a chapter of a PhD thesis of a student. I contacted the editor who had sent me that paper asking what to do and he mentioned that it is a standard and common practice and it shouldn't be considered self plagiarism. So, once again, I am very surprised by the decision made. EDIT: as asked in the comments, here is the email I sent to the editor: Dear Professor XYZ, I am contacting you regarding the submission of my paper to the journal ABC123. As in the subject, the reference number of the manuscript is XXXYYYZZZ. Today I have received an email notifying me that my paper (submitted only 4 days ago) has been rejected. You may find the email attached to this email. The reason for this is: “About 70 % of the article is similar to other documents”. The possible reason for this very high similarity is threefold:  I have published a related conference paper before, containing preliminary results and much less content in general. However, that conference paper is 6 pages long, while the paper submitted to ABC123 is 15 pages long. Therefore, it is mathematically impossible for the conference paper to be the reason of the > 70% similarity, since 6/15 = 40%; The paper has been uploaded on arXiv. This was done the same day in which I sent the paper to your journal. However, this is allowed by Elsevier, as explained here; The contents of the paper are part of my PhD thesis, in particular, of Chapter 5. This is what probably results in the highest similarity, as the article submitted to your journal is based on this chapter. However, Elsevier’s policy with respect to PhD thesis is the following: “Elsevier does not count publication of an academic thesis as prior publication”.  I have run a plagiarism check myself, you can find it attached to this email. This confirms what I have said so far: the similarity of my article is related to my PhD thesis, not to any other previously published works. Given the above explanations, I would kindly ask you if you could reconsider your decision. The plagiarism check returned indeed a similarity higher than 70%, but, as explained above, this is most likely related to my PhD thesis. However, Elsevier does not count PhD thesis as prior publication. Therefore, my paper submitted to ABC123 respects Elsevier’s policies and should therefore be considered a new publication. Thank you for your consideration. Best regards, cholo14

My PhD thesis consisted of two published papers and one submitted paper embedded in some additional framing. For completion of my PhD, I had to upload my thesis to the servers of our academic library, where it is now publicly available. However, afterwards, the third paper from the thesis was rejected after peer review. I performed substantial changes and submitted the manuscript to another journal. They returned it back to me, stating that I exceeded by far the allowed index of similarity (40 % similarity with 35 % similarity of a single source). I spent $100 for a plagiarism check only to find out that the source from which I was accused to have copied a majority of my work, was my own publicly available thesis. As my thesis contains my third (unpublished) manuscript, it naturally has a high similarity with the version I was about to submit. How can I solve this?


I was following this tutorial on YouTube and i was doing the same, maybe i have misplaced or forgot a code somewhere which i can't yet recognize, i'm still new to this,   So the error i'm getting is.    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.www.riderapp.model.Rider.getName()' on a null object reference  at com.example.www.riderapp.Home$5$1.onDataChange(Home.java:391)   This is my Home.java file method    private void loadAllAvailableDrivers() {     //Load all drivers within 3km distance      DatabaseReference driverLocation = FirebaseDatabase.getInstance().getReference(Common.driver_tbl);     GeoFire gf = new GeoFire(driverLocation);      GeoQuery geoQuery = gf.queryAtLocation(new GeoLocation(mLastLocation.getLatitude(),mLastLocation.getLongitude()),distance);     geoQuery.removeAllListeners();     geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {         @Override         public void onKeyEntered(String key, final GeoLocation location) {             // Use key to get email from table users             //Table Users is table when driver register account and update information              FirebaseDatabase.getInstance().getReference(Common.user_driver_tbl)                     .child(key)                     .addListenerForSingleValueEvent(new ValueEventListener() {                         @Override                         public void onDataChange(@NonNull DataSnapshot dataSnapshot) {                             //Because Rider and User model is same properties                             Rider rider = dataSnapshot.getValue(Rider.class);                              //Add drivers to map                              mMap.addMarker(new MarkerOptions()                             .position(new LatLng(location.latitude, location.longitude))                             .flat(true)            ERRR ----->      .title(rider.getName())                             .snippet("Phone : "+rider.getPhone())                             .icon(BitmapDescriptorFactory.fromResource(R.drawable.car)));                           }                          @Override                         public void onCancelled(@NonNull DatabaseError databaseError) {                          }                     });            }          @Override         public void onKeyExited(String key) {          }          @Override         public void onKeyMoved(String key, GeoLocation location) {          }          @Override         public void onGeoQueryReady() {                 if(distance <= LIMIT) // distance just find for 3km                 {                     distance++;                     loadAllAvailableDrivers();                 }         }          @Override         public void onGeoQueryError(DatabaseError error) {          }     });  }   And here is my Rider java class  public class Rider {  private String name,email,phone,password;  public Rider(){  }  public Rider(String name, String email, String phone, String password) {     this.name = name;     this.email = email;     this.phone = phone;     this.password = password; }  public String getName() {     return name; }  public void setName(String name) {     this.name = name; }  public String getEmail() {     return email; }  public void setEmail(String email) {     this.email = email; }  public String getPhone() {     return phone; }  public void setPhone(String phone) {     this.phone = phone; }  public String getPassword() {     return password; }  public void setPassword(String password) {     this.password = password; }   }  I couldn't find why this is really happening, i think it should be a small thing ;)

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I tried Octopus Spam with Crown, but it's not working well.

It's big and empty and I can't get up to the top, what should I do? I can't jump high enough, anti-gravity doesn't seem to do anything either.  My first tactic was to use the octopus summoning crown to create a pile of octopi that I could climb up, but when I teleported to the back of the room they followed me back, trapping me in the entrance.


Directly based off of the question, , what happens if your Darkvision extends past 100 feet?  This question is focused around fact that the Eagle totem features states "You can see up to 1 mile away with no difficulty, able to discern even fine details as though looking at something no more than 100 feet away from you."

Darkvision enables you to see in darkness as if it were dim light (within the first 60/120/180 feet, of course, depending on the quality of your darkvision).  The Eagle totem for the 6th-level Totem Barbarian's Aspect of the Beast feature enables you to ignore your disadvantage from dim light on sight-based Perception checks.  Does that mean that a character with both darkvision and the eagle aspect can make Perception checks (within his darkvision range) without disadvantage, even when in complete darkness ?


I am somewhat new to Visual Studio (2019) and WinForms. I am currently trying to separate the two classes: one for form design and one for the project logic. static class Program {     static void Main() {         Application.SetHighDpiMode(HighDpiMode.SystemAware);         Application.EnableVisualStyles();         Application.SetCompatibleTextRenderingDefault(false);         Application.Run(new Form1());         // more logic     } }  public partial class Form1 : Form {     public Form1() {         InitializeComponent();     }     // design logic }  Currently, I'm having difficulty transferring data between Program and Form1. I have tried creating public members to exchange this information, but I do not know how to access it (since the form is instantiated with the Application class. I have considered leaving Program as is and moving all of the project code into Form1. Replacing the Application class with an instantiation of a form leads to the program not displaying the Form and terminating early. Form1 foo = new Form1();  Is there a way to separate program and design logic, or should I put all the logic into Form1? Thank you for the help.

Is there good example code or a test project for explaining the . There are a lot of explanation links, but I want to have some good example code to show others without reinventing the wheel.


${P(A}{\cup}{B}{\cup}{C)}={P(A)+P(B)+P(C)}-{P(A{\cap}B)}-{P(A{\cap}C)}-{P(B{\cap}C)}+{P(A{\cap}B{\cap}C)}$ Proof: ${P(A{\cup}B{\cup}C)}={P(A{\cup}(B{\cup}C))}$ Associativity ${P(A{\cup}(B{\cup}C))}={P(A)+P(B{\cup}C)-P(A{\cap}(B{\cup}C))}$ Well-known theorem ${P(A{\cap}(B{\cup}C)=P(A{\cap}B){\cup}P(A{\cap}C)}$ Distributive Now I should apply the well-known theorem again. ${P(A{\cap}B){\cup}P(A{\cap}C)=P(A{\cap}B)+P(A{\cap}C)-P((A{\cap}B){\cap}P(A{\cap}C))}$ I'd be finished if I could show this: ${P((A{\cap}B){\cap}P(A{\cap}C))}=P(A{\cap}B{\cap}C)$ Which I could easily justify using a Venn Diagram (which is not acceptable). How else could I do this?   EDIT: The duplicate question doesn't help me. The answer says "and since (A∩C)∩(B∩C)=A∩B∩C, the result is proven." but this is not explained and I DONT want to use a Venn Diagram.

I need some clarification for why the probability of the union of three events is equal to the right side in the following:  $$P(E\cup F\cup G)=P(E)+P(F)+P(G)-P(E\cap F)-P(E\cap G)-P(F\cap G)+P(E\cap F\cap G)$$  What I don't understand is, why is the last term(intersection of all) added back just once, when it was subtracted three times as it appears from a Venn Diagram?  Here on page 3, this is explained but not in enough details that I can understand it:


I was wondering if there was a way of creating a footnote within a table.    Right now I have:   \documentclass[12pt,letterpaper]{report} \usepackage[masters,4committee,nonsequential]{cuthesis} \usepackage{array} \usepackage{graphicx} \usepackage{cite} %\usepackage{subfigure} \usepackage{amsmath} \usepackage[indent,bf]{caption} \usepackage{rotating} \usepackage{setspace} \usepackage{longtable} \usepackage{rotating} \usepackage{float} %\restylefloat{table} \usepackage{subcaption} \usepackage{multirow} \usepackage{amsfonts} \usepackage[table]{xcolor} \usepackage{color} \usepackage{colortbl} \usepackage{alltt} \usepackage{url} \usepackage{verbatim} \usepackage{makecell} \usepackage{placeins} \usepackage{arydshln}  \begin{document}       \begin{table}[ht]     \centering     \caption{Footnote within a table}      \begin{tabular}{ll}       how to enter a footnote & this does not work \footnote{} \\     \end{tabular}     \end{table}  \end{document}   I have tried \usepackage{tablefootnote} and it doesn't seem to work (it actually seems to break something and not be able to compile).  Any help is appreciated!

I would like to have footnotes in tables, but the \footnote command does not work inside a table environment.  Googling one finds that this is , at least in the UK.  That link contains a list of solutions to the problem, but since the author of the FAQ does not believe that this is good style, no comparison is made between the different methods.  I am sure that there are good typographical reasons why in most situations it is undesirable to have footnotes in tables (although I have never come across them), however I have recently felt the need to do just this in a paper I am currently writing.  Therefore I'd like to ask two questions:   What are the arguments against footnotes in tables? If one really must go against the advice in 1., which method (whether considered in the  or not) would you recommend?   Thanks in advance.  Added  In response to ShreevatsaR's comment: I do not much care for where the text of the footnote appears.  I do however insist on the footnote marks being attached to the relevant entries in the table, so that I can avoid having to reference "the second entry in the eighth line of the table", etc...


Regularly I see questions, that do not belong in the correct stack exchange group.  For e.g. duplicates, you can close a question and add a duplicate of the link.  However, sometimes a question belongs to a different stack exchange group, and there is no way except to flag the question and ask it to be moved.  Wouldn't it be more efficient to move it? It could even be voted upon by users.  (example: )

I posted a question which was closed as off-topic and it seems like it could fit on another site in the network. How can I go about moving it there?   What is migration? When can a question be migrated, and who can migrate it? When should I consider migration, and when is it inappropriate? What causes a migration to be blocked and what happens after? What causes a migration to be rejected and what happens after? Anything else I should know about migration?


Is uninstalling via software center the equivalent of apt-get purge?  Or perhaps it is apt-get remove?

When I remove an application already installed through the Software Center. Does it remove the app the same way as doing a purge to it (aptitude purge) or does it remove it like a "remove" (aptitude remove).


Let $(X, \tau)$ be a Hausdorff and compact space, given $x \in X$ we consider the collection $\mathcal{C}= \{C_i\}$ of all the closed and open subsets $C_i$ such that $x \in C_i$. Prove that $C = \cap C_i$ is connected. Prove that $C$ is the connected component of $x$ in $X$.  I tried this, but I am not sure it is right as I did not use X being Hausdorff and compact. Given $\{U,V\}$ such that $C= U \sqcup V$, then $U = C \cap X-V$, w.l.o.g $x \in U$, so $U$ is an open and closed (intersection of closed subsets) subset. Therefore, $C \subset U$ , so $V = \emptyset$  #

I am attempting to solve exercise 1.10.1 from Topology and Geometry by Bredon:  If $X$ is a compact Hausdorff space then show that its quasicomponents are connected (and hence that its quasi-components coincide with its components).  The definition of the relation used for quasi-components is "$d(p) = d(q)$ for every discrete valued map $d$ on $X$."  He gives the hint: If $C$ is a quasi-component, let $C = \cap C_{\alpha}$ where the $C_\alpha$ are the clopen sets containing $C$. If $C$ is disconnected, then $C = A \cup B, A \cap B = \emptyset, A,B$ closed. Let $f:X \to [0,1]$ be $0$ on $A$ and 1 on $B$. Put $U = f^{-1}([0,\frac{1}{2}))$ and apply the following result: Let $X$ be a compact space and let $\{C_\alpha \mid \alpha \in A\}$ be a collection of closed sets, closed with respect to finite intersections. Let $C = \cap C_\alpha$ and suppose that $C \subset U$ with $U$ open. Then $C_\alpha \subset U$ for some $\alpha$.  I don't understand which collection of closed sets to use. If we use the clopen sets $C_\alpha$, and we have that $C \subset U$ but $U \subset X - B$, so $B = \emptyset$, and we don't need some $C_\alpha \subset U$. Furthermore, how would we show that $C \subset U$, it seems to more or less assumes $B = \emptyset$.


So I am trying to install these two packages. I first tried doing the following  sudo apt-get update sudo apt-get install -yy apache2 libapache2-mod-fastcgi php-fpm   this returned:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package libapache2-mod-fastcgi E: Unable to locate package php-fpm   So I then tried:  sudo apt-get update sudo apt-get install -yy apache2  sudo apt-get install -yy libapache2-mod-fastcgi php-fpm   The apache2 will install but for the last line it still gives the same error. I tried looking online if I was perhaps missing a repo, but I couldn't find anything that made me believe so. Next to that I also changed my source.list to have multiverse behind any of them. But this still did not work.. What might be the issue?  my source.list:  deb http://archive.ubuntu.com/ubuntu bionic main multiverse deb http://archive.ubuntu.com/ubuntu bionic-security main multiverse deb http://archive.ubuntu.com/ubuntu bionic-updates main multiverse   After being redirected by one of you to a problem which explained I had to add the universe repo, I did the following:  sudo add-apt-repository universe sudo apt-get update   this gives the error:  Reading package lists... Done Building dependency tree        Reading state information... Done Package libapache2-mod-fastcgi is not available, but is referred to by  another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'libapache2-mod-fastcgi' has no installation candidate   I also tried  sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) main universe restricted multiverse"   Thanks everyone!

How do I get to the Universe Repository in supported versions of Ubuntu?


If rm dir -r has removed just partial content of dir/dir1/ (and I cancelled rm), has it not removed anything in dir/dir2/ if dir/dir2/ still exists and contains something? My OS is Ubuntu 14.04 and filesystem ext4.  I heard , but can my question be answered more surely?  My OS is 64bit Ubuntu 14.04 with ext4 filesystem.  Knowing if rm completely remove a subdir before removing another subdir is weaker than knowing the order of rm operating in. So my question is not duplicate of the linked one.

Is there some order of operations to rm? I performed rm on a large directory and am curious where I should look to see what might have been deleted. Does rm work on files first, then directories? Or is it based on some information in the inode table?  Specs: rm from GNU coreutils 8.22 system: Arch Linux running on a beagleboneblack filesystem operating on was an external Seagate HDD (ext4) using USB 2.0.  Backstory:  I was performing some directory cleanup and performed  cp -r A/ B/ C/ Dest/   Unwittingly, I followed that up with   rm -r A/ B/ C/ Dest/   when I meant to simply perform   rm -r A/ B/ C/   I caught this and hit Ctrl+C before too long had passed. Specifically, it was < 3 seconds as I was using the time command in conjunction with rm & cp.  I went in and examined Dest/ expecting it to be non-existent, but lo and behold it was whole and appeared to not be affected. This is a bit surprising as A/ B/ C/ were quite small. Maybe 100–200 MB total. Dest/ however, is just shy of 1TB. Performing an ls on Dest/ showed that there were both files and directories at both ends of the alphabet (e.g. AFile.txt .... .... Zoo.txt).   Did I get lucky and cancelled the rm before it wrought havoc on my Dest/ directory? Is rm really that slow (thankfully!)?   If not, how does rm go about recursively removing things such that I can guess what might have been lost?  I'm not really expecting to recover what I might have lost, just curious what potentially was blown away.


I have created a KeyListener and whenever I press W (the specified key) nothing prints out like I told it to. I have tried looking around stack exchange and many other forums to come to no conclusion.  Code:  package com.software.manders;  import java.awt.FlowLayout; import java.awt.event.KeyEvent; import java.awt.event.KeyListener;  import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel;  public class game implements KeyListener {     //0 = English, 1 = Korean.     public static int languageStatus = 0;     public static int gameStatus = 0;     static JFrame frame = new JFrame();      public static void frameMaker() {         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         frame.setVisible(true);         frame.setResizable(false);         frame.setTitle("경기");         frame.setSize(600, 600);          new game();     }      public game() {         if (gameStatus == 0) {             JPanel p = new JPanel();             JLabel lab1 = new JLabel();             p.setLayout(new FlowLayout());             p.add(lab1 = new JLabel("Please select a language : "));              JLabel lab2 = new JLabel();             p.add(lab2 = new JLabel("Press A for English"));              JLabel lab3 = new JLabel();             p.add(lab3 = new JLabel("Press B for Korean"));              frame.add(p);         }     }      @Override     public void keyPressed(KeyEvent e) {         int id = e.getKeyCode();          if (id == KeyEvent.VK_W) {             System.out.println("W is pressed");         }     }      @Override     public void keyReleased(KeyEvent e) {         int id = e.getKeyCode();          if (id == KeyEvent.VK_W) {             System.out.println("W is released");         }     }      @Override     public void keyTyped(KeyEvent e) {      }      public static void main(String[] args) {         frameMaker();     } }

I'm trying to implement a KeyListener for my JFrame. On the constructor, I'm using this code:  System.out.println("test"); addKeyListener(new KeyListener() {     public void keyPressed(KeyEvent e) { System.out.println( "tester"); }      public void keyReleased(KeyEvent e) { System.out.println("2test2"); }      public void keyTyped(KeyEvent e) { System.out.println("3test3"); } });   When I run it, the test message comes up in my console. However, when I press a key, I don't get any of the other messages, as if the KeyListener was not even there.  I was thinking that it could be because the focus is not on the JFrame and so they KeyListener doesn't receive any events.  But, I'm pretty sure it is.  Is there something that I am missing?


Sorry if somebody has already asked this question, I haven't found anything else.   When you install Ubuntu, some sort of program is run, like where you set different options for your OS installation.  Does anyone know what the software is being run?  Thanks.

I need to log a bug against the 12.04 installer (the installation wizard that you run off the CD/DVD). What is the package name for this application?


I have roughly 7 columns on each line, I want to print two specific columns then the remaining columns after the last specified one, example:  awk -F: {' print $2 ":" $6 '} a.txt   would print columns 2 and 6 from a.txt. How would I then go onto print the remaining columns after $6?  So example of input/output would be:      column2:column6:column7:column8:column9...

if I have a csv file in the following format:  column1,column2,column3,column4,column5,column6,column7,column8   and I want awk to only print columns 2 till 7 I would use:  awk -F',' '{print $2 "," $3 "," $4 "," $5 "," $6 "," $7}' file.csv   and get:  column2,column3,column4,column5,column6,column7   is there a way to concatenate the columns 2-7 to simplify the command. As I'm thinking of a file with quite a bit more columns, my awk command would get horribly long.


So I've been trying to figure out prototypal inheritance in Javascript and I'm still confused on one point. Let's say I want to make a constructor function for a person with a few functions of it's own.  function Person(name) {   this.name = name;   this.sayName = function() {     console.log("My name is " + name);   } }  var john = new Person("John");  john.sayName();   So in this case I've created an object and called a function, however this doesn't seem to be the efficient way to do it. Another example I've seen this is this:  function Person(name) {   this.name = name; } Person.prototype.sayName = function() {   console.log("My name is " + name); }  var john = new Person("John");  john.sayName();   Now I've read that the second object is more efficient because it's not storing the sayName function within itself, instead it's going up the prototype chain until it finds it within Persons prototype object.  What I'm unsure about is which I should use for complicated constructor functions. The first snippet, in my opinion, is much much easier to read than the second because there is a clear hierarchical structure to it, but the second snippet is supposedly more efficient.   In a real world scenario, which style of constructor function would I be more likely to use?  Edit: I have a follow up question. Is there any way to make the second snippet more readable?

What's the difference between  var A = function () {     this.x = function () {         //do something     }; };   and  var A = function () { }; A.prototype.x = function () {     //do something };


I want to see the source code of a apt package to install the software manually without root privilege.   I googled and the way to see the source code is to use apt source. So I did but not worked as follows.    sudo apt-get source silversearcher-ag Reading package lists... Done E: Unable to find a source package for silversearcher-ag   I googled some more posts and I noticed I have to uncomment deb-src lines in sources.list file, according to .   So I modified the file as follows. However even after that there's same error message to me. How to solve this issue? Thanks.   diff --git a/sources.list b/sources.list index d925310..3f579e3 100644 --- a/sources.list +++ b/sources.list @@ -2,9 +2,9 @@ deb http://archive.ubuntu.com/ubuntu/ xenial main restricted universe multiverse  deb http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted universe multiverse  deb http://security.ubuntu.com/ubuntu/ xenial-security main restricted universe multiverse  deb [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable -deb-src [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable -deb-src [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable +# deb-src [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable +# deb-src [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable  deb [arch=i386,amd64] https://cran.rstudio.com/bin/linux/ubuntu xenial/ -deb-src [arch=i386,amd64] https://cran.rstudio.com/bin/linux/ubuntu xenial/ +# deb-src [arch=i386,amd64] https://cran.rstudio.com/bin/linux/ubuntu xenial/  deb https://dl.winehq.org/wine-builds/ubuntu/ xenial main -deb-src https://dl.winehq.org/wine-builds/ubuntu/ xenial main +# deb-src https://dl.winehq.org/wine-builds/ubuntu/ xenial main

I need to install build-dependencies of something, how do I ensure the source code section of my software sources is enabled?


Prove That $6^n -1$ is composite $\forall n>1 \in \mathbb{N}$

I did some mathematical induction problems on divisibility   $9^n$ $-$ $2^n$ is divisible by 7. $4^n$ $-$ $1$ is divisible by 3. $9^n$ $-$ $4^n$ is divisible by 5.   Can these be generalized as $a^n$ $-$ $b^n$$ = (a-b)N$, where N is an integer? But why is $a^n$ $-$ $b^n$$ = (a-b)N$ ?  I also see that $6^n$ $- 5n + 4$ is divisible by $5$ which is $6-5+4$ and $7^n$$+3n + 8$ is divisible by $9$ which is $7+3+8=18=9\cdot2$.  Are they just a coincidence or is there a theory behind?  Is it about modular arithmetic?


I seem to think that it should be zero as well because being a constant zero can be taken outside the integral and whatever be the answer of the remaining constant integration it is finite. However my textbook implies that it is the arbitrary constant c.

I am trying to convince my friend that the integral of $0$ is $C$, where $C$ is an arbitrary constant. He can't seem to grasp this concept. Can you guys help me out here? He keeps saying it is $0$.


I am a novice for graphic design.  I have a low quality image which is given by my friend, its size is really small, but we want to make it bigger and clearer so that we can use it as a banner or logo or etc.    So my question is what is the easiest way to get a better quality image from a given(smaller, low quality) image?   Should I manually draw it, and how, what tools to use? Or is there a way which I can easily convert it to a vector and then increase the size and then save it back as a png?

I am an novice.  I want to draw this picture   But I meet a problem  I found a heart outline image from the internet and dropped on my ps file. When I was trying to fill this heart with a pure color, it becomes something like this


I was in the shower one day washing my hair, and noticed that the water falling off my hair formed perfect streams that ceased to break into droplets for quiet some distance (probably about 5-6 cm).  I have kinda long hair so that greatly aided in the formation of the streams.  I decided to see what would happen if the stream collided with a relatively flat perpendicular surface.  I put my finger under the stream and was pleasantly surprised to see ripples upstream of the "impact".  I then decided to move my finger up and noticed that these ripples became increasingly pronounced and seemingly formed a "wave".  When very close to the origin of the stream (my hair) they began to turn into spherical beads.  I decided to film the phenomenon to show you guys, and further below I have some theories as to what may be happening.    One theory I had was that the ripples are caused by a longitudinal wave traveling up stream, and since the compression zones are in water, they manifest as high pressure zones that cause the stream to bulge outwards as the surface tension holding the stream together is fairly flexible.  The wavelength is most likely dependent (either directly or indirectly) on the speed of the falling as when I use faster flowing streams the wavelngth is a lot shorter, possible due to the faster impact.  This may also be why when the impact is near the origin the stream begins to bulge more dramatically as the wavelength is a lot shorter due to the water not accelerating from free fall for as long and colliding with less force.    Another theory I had as to why the wavelength changes with finger height is that as you move down the stream since the water is moving a lot faster and the differences in speed become greater between the individual particles the water begins to decrease in density (thing spaghettification near black holes).  If this does occur I don't believe it is as strong of a factor as the stream thins as it falls.  This shows that rather than the spaces between the particles growing and remaining, they more likely come back together and instead manifest as the thinning of the stream.  If the cause is by both states above I may be able to formulate the density of the falling water based on the wavelength, but this is just a loose thought I have and needs more support.    I may be able to figure out if the cause is speed by looking at whether the wavelength changes as a parabolic function of finger height (as the impact speed and does, and this would possible show they're linked) but this would only be the case if impact shock waves wavelengths were linearly proportional to the impacts impulse.  I would love to hear what you guys think of this idea.  My final, weaker theory I had was that the ripples are caused by the surface of the water attempting to establish a smooth transition onto the perpendicular plane, and as it curves outward, it causes a bend in the opposite way upstream which therefore causes another bend opposite to that until it smoothens out.  I attempted to crudely illustrate this below.     These are lose thoughts that came to mind to support the theory, and am eager to get any feedback and share any results with you guys.  If you have a completely new theory or disprove my theories please post them below, any information may help bring this question to a close.  I'm currently doing a physics extended essay, and am willing to drop my current essay for something related to this phenomenon  as it seems very interesting and would be pleasure writing about.  EDIT:  A friend proposed that the waves are propagated from small currents resulting from the bottles/taps shape or the hole shape.  I tested this using a uniform bowl and drilled a hole in it instead of poking one to get a more uniform hole and got identical results.

This is a simple experiment that anyone can do at home. Open your tap so that the water maintains a laminar flow, and the cross section of flow is considerably thin. Place your finger 3-4 cm below the flow. A beautiful wave-like pattern is observed on surface of flowing water, near the region of your finger. Changing the position of finger changes the 'wave-length' of the wave.   The attached picture shows how to do this experiment, though the resolution is not clear.    What is the explanation for this phenomena? Probably a harder question would be if there is an intuitive explanation for it. Thanks!      ${\bf Edit:}$ I observed a similar phenomena in the swimming pool...when the water is still, move your hand slowly along the surface of the water. It causes a 'bump' in the water, which decays away in a wave-like pattern in front of your hand. Clearly they are the same phenomena: water falling on the hand or hand moving against the water.  The answers below are very interesting (Thanks!). And as far as I can see, they are still being debated, suggesting that the phenomena is more non-trivial that it appears to be. I had accepted an answer earlier, but I am now taking it back, as I did not completely understand it. Looking forward to further discussion on it. It would be most exciting to find an answer that is elementary: without resorting to complex terminologies of fluid mechanics.


Is there an actual definition of "forgetful functor?"  defines it in terms of functors from algebraic categories to the category of sets, but then says, "Other forgetful functors..." which seems an odd way to "define" something. In any event, it seems to exclude, say, the functor which takes topological groups to topological spaces (or groups.)   contains no definition, just lots of examples.  Is this one of those cases where we don't need a strict definition, we just recognize it when we see it?

One sometimes hears about "the forgetful functor $Ab \to Grp$." Given that the image of an object under this functor is still abelian, in what sense is this "forgetful"?


I Want to know how to design good class A amplifier of 10W for 8ohm load. with common emitter stage for input and emitter follower for output.with minimum component quantity.first stage is below Vc is about 12.34V and Ic is 6mA maximum 10 mA. I have 25 v 4A supply please help with detail.

Hi I make this class A amplifier but how to replace R5 (10 ohm/10 W) with transistor because its getting really hot and how to achieve up to 10 Watt with +/- supply. I have +/-25v with 4A please help


Let $X$ be a Banach space and $T\in B(X)$. Show that $$\bigcap_{K\in K(X)} \sigma(T+K)= \sigma(T)\setminus \{\lambda : \lambda I-T \text{ is a Fredhold operator with index zero}\}.$$  I looked at the set $\{\lambda : \lambda I-T \text{ is a Fredhold operator with index zero}\}$. Here $K(X)$ is the space of compact operators. If $\lambda I-T$ is Fredholm and has index zero, i.e. its nullity is equal to its deficiency, then it is an isomprphism, i.e. invertible, so by definition of spectrum, $\lambda \notin \sigma(T)$ so this set contains the scalars which don't belong to the spectrum of $T$. We can look at $\sigma(T+K)$ where $K$ is compact. $$\sigma(T+K)=\{\lambda : \lambda*I-(T+K) \text{ is not invertible}\}$$ However it is not obvious to me how to connect things together. Edited: This question has an answer here  However I need a detailed explanation for the seconed side in the proof. Any help will be Appreciated!

If $X$ is an infinite-dimensional Banach space and $u\in B(X)$,why the following equality is true?  $$\bigcap_{v\in K(X)}\sigma(u+v) =\sigma(u) \setminus \{\lambda \in\mathbb{C}\mid u - \lambda \text{ is Fredholm of index zero} \}$$  The index of $u\in A$ is defined to be  $$\operatorname{ind}(u)=\operatorname{nul}(u)-\operatorname{def}(u)$$ where co-dimension of $u(X)$ in $Y$ be denoted by $\operatorname{def}(u)$ and $\dim(\ker(u))$ denoted by $\operatorname{nul}(u)$  $u\in B(X,Y)$ is Fredholm operator, if $\ker(u)$ is finite-dimensional and $u(X)$ is finite-co-dimensional in $Y$  $$K(X,X):=K(X)=\{u : X \longrightarrow X\mid u\text{ is compact operator}\} $$


I had the hardest time figuring out how to get to the revision history by links over the past few days ... it would be really nice if there was just a link named "history" next to "link", "flag", etc. to get to it. This would also make it easy to find on questions/answers that had had no edits yet.  (Oh, for anyone else trying to figure out where the links are: look at the edit date, to the left of the asking date, on questions/answers that show up as edited. For other questions/answers, use the URL template http://<site>/posts/<PostId>/revisions.)

In the latest  I saw this:     2013-02-18: The revision history of a question that was closed as a duplicate is now showing the chosen originals as part of the "Closed as duplicate" notice.   That sounds cool, so I went to go see what it looks like and realized that questions with , but no edits, don't have an "edited <date>" link to click.  This applies to questions which had a bounty posted, or have been closed, reopened, locked, deleted, etc.  Examples:   , revisions:  , revisions:          I realize I can manually type the URL:  https://meta.stackoverflow.com/posts/168761/revisions   But it would be nice to simply click. It could say "revised" instead of "edited" if there were no edits:


Can someone tell me how to overlay the texture for the eyes? If I go to texture, the outfit isn't there. I have the same problem with other textures as well.

I'm designing this animal-type creature, and want to add a transparent .png image to its face with the face features (object has a subsurf). On the left is the image with the features, on the right is the part of the object where I want it to be.    I tried to import the image as a plane, but matching the shape of the plane with the face didn't work, and the lines of the face left shadows on the head, and could be seen as a different object from some angles (although it's the closest I've gotten yet). It looked like this:    So , I tried selecting the faces of the head that the features should go over, and create a new material for it. Unfortunately, since the .png is transparent, the result produced was this:    (where it's impossible to tell the transparency from a black background default color, and where I wouldn't know where to start to adjust size and position).  I also tried UV mapping, but then the whole object became black with the features repeated all over.   Is it something I have to go into Nodes for? I'm kind of stuck here. Creating a new material and applying it is simple, but applying a material that is an image is a bit more complex it seems... Ideally, I would reproduce the same technique for the adhesive bandage on its arm (seen on the right of image 1).


I'm using Ubuntu 12.04 LTS,and I have a laptop with good configuration. I would like to install windows 8/7 inside my Ubuntu OS. Is it possible? If yes, what is the process? Can I install it from DVD?

I have already dual systems : Windows 7 and Ubuntu installed on my laptop. The Windows 7 had been installed when I bought this laptop, and I don't have a CD.  I just installed VitrualBox under Ubuntu, hoping that I could install another Windows in this virtual machine, so that I could run some applications of Windows even under Ubuntu.  But it seems that I need a CD or ISO of Windows to boot inside this virtual machine. Otherwise, there is an error: FATAL: No bootable medium found! System halted. My question is where I could find a CD or ISO?  At the moment, I am downloading ISO from this , but do not know if it will work. By the way, I am not sure if I should pick the 32-bit or 64-bit? As my CPU is 64-bit but my Ubuntu is i386.  Could anyone help? Thank you very much.


I've found myself recently in a particularly annoying situation and I'd like to know what can be done in this specific situation.  There's a question asked by a newbie user (not me) on SO, and while I was looking at a solution for it, another user with more than 50k rep closed the question as a duplicate.  However, the solution proposed in the duplicate link wasn't the answer to the problem, since the latter was caused by another thing.  I asked politely and repeatedly to the closing user to reopen the question in order to let me post an answer and solve the problem of the newbie user, but he/she didn't, going on in spamming various excuses in the comments as the reasons why he won't do that (and actually, he never provided a viable solution to the question).  In the end, I gave the code to solve the problem in a comment to the OP, without being able to elaborate further on it.  Is there anything someone can do when a user behaves this way? It seems wrong to me that any user can abuse of his "high rep power" this way.

To reopen a closed question,  must agree that the question is suitable for the site and cast votes to reopen the question. But:  How does one actually vote to reopen? Is there a reputation level that you must have before you can see this function? Or do I just leave a comment along the lines of, "I vote to reopen"? What happens if someone with less than 3000 reputation leaves a comment that they wish to vote to reopen? How can one draw attention to their closed questions? Is it done via a posting new question? Or do you edit the closed question?   Related:  For more information, see "" in the .


Hi I am trying to find out for what values of the real parameter does the integral $$ I=\int_0^\infty \frac{\sin x}{x^s}dx $$ (a) convergent and (b) absolutely convergent.     I know that the integral is convergent if $s=1$ since $$ \int_0^\infty \frac{\sin x}{x}dx=\frac{\pi}{2}. $$ For $s=0$ it is easy to see divergent integral since $\int_0^\infty \sin x\, dx$ is divergent.  However I am stuck on figuring out when it is convergent AND or absolutely convergent.  I know to check for absolute convergence I can determine for an arbitrary series $\sum_{n=0}^\infty a_n$ by considering $$ \sum_{n=0}^\infty |a_n|. $$ If it helps also $$\sin x=\sum_{n=0}^\infty \frac{(-1)^{2n+1}}{(2n+1)!} {x^{2n+1}}$$. Thank you all

For what values of $\gamma\geq 0$ does the improper integral $$\int_0^\infty \frac{\sin(t)}{t^\gamma} \mathrm{d}t$$ converge?   In order to avoid two "critical points" $0$ and $+\infty$ I've thought that it would be easier to test the convergence of the sum (is this coherent?): $$ \int_0^1 \frac{\sin(t)}{t^\gamma}\mathrm{d}t + \int_1^\infty \frac{\sin(t)}{t^\gamma}\mathrm{d}t. $$ For the second integral, it converges if $\gamma > 1$ (comparision) and also converges if $0 <\gamma \leq 1$. I'm stuck on proving the last part and the fact that the first integral converges for $\gamma < 2$. Any help would be appreciated. Thanks in advance.  PD: I've checked the answers for  but I would not like to solve this integral using $(n\pi,(n+1)\pi)$ intervals.


In how many ways can $105$ be written as the sum of an increasing sequence of two or more consecutive positive integers?   I got the above question for small numbers. For example I took 15.  Since $15=3\times5$  $15=3+3+3+3+3=(3-2)+(3-1)+(3)+(3+1)+(3+2)=1+2+3+4+5$  $15=5+5+5=(5-1)+(5)+(5+1)=4+5+6$  So there are $2$ ways for $15.$ Can I apply this method to $105.$ How ?

All the positive numbers can be expressed as a sum of one, two or more consecutive positive integers. For example $9$ can be expressed in three such ways, $2+3+4$, $4+5$ or simply  $9$. In how many ways can a number be expressed as a sum of consecutive numbers?  In how many ways can this work for $65$?  Here, for $9$ answer is $3$, for $10$ answer is $3$, for $11$ answer is $2$.


I am using a Mac Machine with the following LaTeX Softwares:   MacTEX: as the main LaTeX kernel  TexStudio: as the LaTeX editor    In part of the document I have created, I try to import a vector graphic image in *.eps format:   \begin{figure}     \begin{center}        \begin{tabular}{cc}         \includegraphics[width=0.450\linewidth]{images/p1}&          \includegraphics[width=0.450\linewidth]{images/p2}\\          (a)OLS & (b)RR      \end{tabular}   \end{center} \end{figure}   p1 and p2are p1.eps and p2.eps images.I include the following packages as well on top of the code:  \usepackage{graphicx} \usepackage{epstopdf}   After this, I am getting a stupid error with regard to eps to pdf conversion.  ! Package pdftex.def Error: File `images/p1-eps-converted-to.pdf' not found. ! Package pdftex.def Error: File `images/p2-eps-converted-to.pdf' not found.   I have tried several options but still cannot see the images in my machine. What can I do to overcome the issue please?

I'm using TeXStudio on Mac OS X 10.7.4.  The problem is that the EPS to PDF conversion is somehow broken:  \usepackage[pdftex]{graphicx} \graphicspath{{img/}} \DeclareGraphicsExtensions{.pdf,.jpeg,.png} ... \begin{figure}[!t] \centering \includegraphics[width=3.5in]{TCP_VC_TD_AVE_CONNS_ACT} \caption{Simulation Results} \label{fig_sim} \end{figure} ...   I've got an EPS file in: img/TCP_VC_TD_AVE_CONNS_ACT.eps  Log:  Package epstopdf Info: Source file: <img/TCP_VC_TD_AVE_CONNS_ACT.eps> (epstopdf)                    date: 2012-10-12 16:44:32 (epstopdf)                    size: 210073 bytes (epstopdf)             Output file: <img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted- to.pdf> (epstopdf)             Command: <epstopdf --outfile=img/TCP_VC_TD_AVE_CONNS_ACT -eps-converted-to.pdf img/TCP_VC_TD_AVE_CONNS_ACT.eps> (epstopdf)             \includegraphics on input line 94. runsystem(epstopdf --outfile=img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted-to.pdf i mg/TCP_VC_TD_AVE_CONNS_ACT.eps)...executed.  Package epstopdf Info: Result file: <img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted- to.pdf>.  ! Package pdftex.def Error: File `img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted-to. pdf' not found.   The required img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted-to.pdf file is never created.  TeXStudio compiles with (I've added -shell-escape, from other posts):  /usr/texbin/pdflatex -synctex=1 -interaction=nonstopmode -shell-escape %.tex   Can anybody assist?  EDIT - A minimal file breaks as well:  \documentclass{article} \usepackage{graphicx} \begin{document} \includegraphics{img/TCP_VC_TD_AVE_CONNS_ACT.eps} \end{document}   Log:  Package epstopdf Info: Source file: <img/TCP_VC_TD_AVE_CONNS_ACT.eps> (epstopdf)                    date: 2012-10-12 16:44:32 (epstopdf)                    size: 210073 bytes (epstopdf)             Output file: <img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted- to.pdf> (epstopdf)             Command: <epstopdf --outfile=img/TCP_VC_TD_AVE_CONNS_ACT -eps-converted-to.pdf img/TCP_VC_TD_AVE_CONNS_ACT.eps> (epstopdf)             \includegraphics on input line 4. runsystem(epstopdf --outfile=img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted-to.pdf i mg/TCP_VC_TD_AVE_CONNS_ACT.eps)...executed.  Package epstopdf Info: Result file: <img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted- to.pdf>.  ! Package pdftex.def Error: File `img/TCP_VC_TD_AVE_CONNS_ACT-eps-converted-to. pdf' not found.


Have installed Ubuntu 13.04 alongside Windows Vista. I was able to boot either for a while but now only Ubuntu - if I select Vista from menu it returns to the menu after failing to Boot. Have tried System Repair on Vista but doesn't correct problem. There must be a simple solution to this - I really don't want to reinstall Vista from old Recovery Discs. The guys at Ubuntu can't push this dual use with it failing so easily! Or can they? Have looked at some related problems but no help to me.    I ran Boot-Repair as per forum advice. Rebooted but still can't get Vista.  url was   (Also sent to boot.repair@gmail.com)

I'm very new to Ubuntu, and have come to this point that I can't boot back to my Windows Vista anymore.  I thought that I would get some kind of dual boot in the beginning when booting my computer, but this doesn't seem too happen and I don't have the slightest idea on how to fix this. I was looking for help here at askubuntu, but I couldn't seem to find anything. I'm too new with this software.  I'll need hints and tips on how to fix this  Thanks for your time folks!


I'm looking for a way to remove text editor from page because i'm using Beaver Builder plugin (for building my pages).  like you see in the picture bellow, i have 2 tabs. I want to remove text editor tab (in the red color).  Thanks in advance.

I dont want to use the WYSIWYG at the top of my Custom Post Type. I want to use a custom field textarea that i can place at bottom of my list of custom fields instead.  Is this possible?


i just installed ubuntu 14.04 and when i'am connected with wifi i can't post or register on any site or forum there is no problem when iam using wired connection  i've got broadcom 43142

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


Plus, to the proof any p-group G is solvable,although Z(G) is normal to G and which is abelian, but G/Z(G) is not abelian, so what is the chain subgroup to  show that G is solvable?

I recently read the well known theorem that for a group $G$ and $H$ a normal subgroup of $G$, then $G$ is solvable if and only if $H$ and $G/H$ are solvable. In my book, only the fact that $G$ is solvable implies $H$ is solvable was proven. I was able to show that if $H$ and $G/H$ are solvable, then so is $G$, but I can't quite show that $G$ is solvable implies $G/H$ is solvable.   My idea was this. Since $G$ is solvable, there exists a normal abelian tower $$ G=G_0\supset G_1\supset\cdots\supset G_r=\{e\}. $$ I let $K_i=G_i/(H\cap G_i)$, in hopes of getting a sequence $$ G/H\supset K_1\supset\cdots\supset K_r=\{e\}. $$ My hunch is that the above is also a normal abelian tower. However, I'm having trouble verifying that $K_{i+1}\unlhd K_i$ and that $K_i/K_{i+1}$ is abelian.  Writing $H_i=H\cap G_i$, I take $gH_{i+1}\in K_{i+1}$ for some $g\in G_{i+1}$. If $g'H_i\in K_i$, then I want to show $g'H_igH_{i+1}g'^{-1}H_i$ is still in $K_{i+1}$, but manipulating the cosets threw me off. I also tried to use either the second or third isomorphism theorems to show that $K_i/K_{i+1}$ is abelian, but I'm not clear on how to apply it exactly. I'd be grateful to see how this result comes through. Thank you.


I was setting path for anaconda. an answer to a question  has the following solution. I searched for .bash_profile, but I can't seem to find it. How do I setup this file and get it to run on startup?

Whenever I open a terminal, I have to write  export PATH=~/anaconda3/bin:$PATH   to use any feature of anaconda  I want a persistent path.


Define two sets: $\Sigma_1$ and $\Sigma_2$ where we have that $a$ is  odd (i.e. $a=2n+1$ for some $n\in \mathbb{N}$)  and $b\in \mathbb{N}$, $\Sigma_1 = \Big\{ \frac{2}{a},\frac{2}{a-2},\frac{2}{a-4},...,\frac{2}{a-(a-1)},$ $\frac{2+4}{a+2},\frac{2+4}{a},\frac{2+4}{a-2},...,\frac{2+4}{a-(a-1)},$ $\frac{2+8}{a+4},...,\frac{2+8}{a-2},...,\frac{2+8}{a-(a-1)},$ $\vdots$ $\frac{2+4\lfloor\frac{b}{2}\rfloor}{a+\lfloor\frac{b}{2}\rfloor},\frac{2+4\lfloor\frac{b}{2}\rfloor}{a+\lfloor\frac{b}{2}\rfloor-2},...,\frac{2+4\lfloor\frac{b}{2}\rfloor}{a-(a-1)},$ $\frac{2+4(\lfloor\frac{b}{2}\rfloor+1)}{a+\lfloor\frac{b}{2}\rfloor},\frac{2+4(\lfloor\frac{b}{2}\rfloor+1)}{a+\lfloor\frac{b}{2}\rfloor-2},...,\frac{2+4(\lfloor\frac{b}{2}\rfloor+1)}{a-(a-1),}$ $\frac{2+4(\lfloor\frac{b}{2}\rfloor+2)}{a+\lfloor\frac{b}{2}\rfloor-2},\frac{2+4(\lfloor\frac{b}{2}\rfloor+2)}{a+\lfloor\frac{b}{2}\rfloor-4},...,\frac{2+4(\lfloor\frac{b}{2}\rfloor+2)}{a-(a-1)}$ $\vdots$ $\frac{2+4b}{a},\frac{2+4b}{a-2},...,\frac{2+4b}{a-(a-1)} \Big\}$ and $\Sigma_2 = \Big\{ \frac{2}{\lceil\frac{a}{2}\rceil}, \frac{2}{\lceil\frac{a}{2}\rceil-1},\frac{2}{\lceil\frac{a}{2}\rceil-2},...,\frac{2}{1}$ $\frac{2+2}{\lceil\frac{a}{2}\rceil+1},\frac{2+2}{\lceil\frac{a}{2}\rceil},\frac{2+2}{\lceil\frac{a}{2}\rceil-1},...,\frac{2+2}{1},$ $\vdots$ $\frac{2+2(\lfloor\frac{b}{2}\rfloor-1)}{\lceil\frac{a}{2}\rceil+(\lfloor\frac{b}{2}\rfloor-1)},\frac{2+2(\lfloor\frac{b}{2}\rfloor-1)}{\lceil\frac{a}{2}\rceil+(\lfloor\frac{b}{2}\rfloor-2)},...,\frac{2+2(\lfloor\frac{b}{2}\rfloor-1)}{1}$ $\frac{2+2\lfloor\frac{b}{2}\rfloor}{\lceil\frac{a}{2}\rceil+\lfloor\frac{b}{2}\rfloor},...,\frac{2+2\lfloor\frac{b}{2}\rfloor}{1},$ $\frac{2+2(\lfloor\frac{b}{2}\rfloor+1)}{\lceil\frac{a}{2}\rceil+\lfloor\frac{b}{2}\rfloor-1},...,\frac{2+2(\lfloor\frac{b}{2}\rfloor+1)}{1},$ $\frac{2+(\lfloor\frac{b}{2}\rfloor+2)}{\lceil\frac{a}{2}\rceil+\lfloor\frac{b}{2}\rfloor-2},...,\frac{2+(\lfloor\frac{b}{2}\rfloor+2)}{1}$ $\vdots$ $\frac{2+2b}{\lceil\frac{a}{2}\rceil-1},...,\frac{2+2b}{1} \Big\}$ The question is, how do I determine the cardinality of the intersection of these two sets i.e. how would I compute the value $|\Sigma_1 \cap \Sigma_2|$? Note that duplicates may appear within both sets such as $\frac{1}{2}=\frac{2}{4}=\frac{4}{8}$ etc. Therefore we must make sure that for each fraction $\frac{n}{m}$ we have $\text{gcd}(n,m)=1$. I am aware of the existence of , which really might help here. Unfortunately I struggle simplifying the formulas of $\Sigma_i$'s to simpler forms. My question is if these expressions may be simplified in any way or there is a way of finding the cardinality of $|\Sigma_1 \cap \Sigma_2|$?