Conventional current as a concept is easily understood until the professor says what actually takes place is electron flow. Electron flow moves in the opposite direction as conventional current.  Why doesn't electrical engineering text books teach electron flow current since it reflects the actual situation more accurately?  I am sure I have missed out something. Can the more learned members here enlighten a confused person?

If Conventional Current is backwards, how do I look at something like this schematic and trace the flow of current?  I'd like to follow the design linearly from positive to negative.    When the battery is on, does current go to 8, then 4, then through R1 and so on?  Does the current get "back around" to the side of the capacitor, 1, and the speaker eventually (though fast)?  How can this be so if in reality electrons flow from negative to positive?  Edit:  If the current were water here, how would I see that physically on the wiring, as if they were pipes?


How can I open an app from my app in Swift? I need open contacts book to select the contact and save on my app, but I don't know how to do this.. I'm reading how read the contacts and show into a table view but not about how to open the contact book app.  And also I'm reading how to open with UIApplication.sharedApplication() but I only show how to open urls...  There is some form to make this?  Thanks!

Is it possible to launch any arbitrary iPhone application from within another app?, For example in my application if I want the user to push a button and launch right into the Phone app (close the current app, open the Phone app).  would this be possible? I know this can be done for making phone calls with the tel URL link, but I want to instead just have the Phone app launch without dialing any specific number.


I have just installed Ubuntu and it's great. I  also installed Flash by following .  After I wanted to download a video from Youtube and I installed a software called Miro that looks like some sort of browser. When i navigated to Youtube it says no Flash Player downloaded. But if I use Firefox, Youtube  works fine. Help pls

I recently downloaded Miro which I used to use with great satisfaction in Windows, however on Ubuntu, Miro cannot play Flash videos or sites because of Flash compatibility issues. Yet I have Flash installed and working great in other applications.  Is there a way to get it working with Miro?  Thanks


My external HDD suddenly started reporting as "931.51 GB RAW (Primary)" in Windows disk management.   I tried using DiskInternals Partition Recovery, which indeed reported the drive being only seen as RAW, easily found a partition at sector 2048, spanning the full size of the disk, detected an NTFS system on it... and then it completely failed to find any files.  DISKPART sees the partition as RAW.  ChkDsk H:, however, DOES detect it as NTFS and checks the filesystem (finding indexing errors in file descriptor 5, which is root folder ".", so thus far I only ran it in read-only mode out of caution).  MiniTool, another recovery program, immediately noticed the disk, with a correct volume label and explorable contents, even without running a recovery pass, but the free version doesn't let me copy files.  Finally, TestDisk is able to read the disk's contents without any problems, without running a specialized recovery pass - it accesses the NTFS system as if everything was fine.  Reading the disk in hex mode, I see the MBR area is completely empty (all zeroes) except for a serial number and one, seemingly correct, partition entry:  0000000000: 00 00 00 00 00 00 00 00 | 00 00 00 00 00 00 00 00 .... 00000001A0: 00 00 00 00 00 00 00 00 | 00 00 00 00 00 00 00 00 00000001B0: 00 00 00 00 00 00 00 00 │ 39 72 8E 13 00 00 00 20  <- serial, part.type 00000001C0: 21 00 07 FE FF FF 00 08 │ 00 00 AC 65 70 74 00 00  <- partition 1 00000001D0: 00 00 00 00 00 00 00 00 │ 00 00 00 00 00 00 00 00 00000001E0: 00 00 00 00 00 00 00 00 │ 00 00 00 00 00 00 00 00 00000001F0: 00 00 00 00 00 00 00 00 │ 00 00 00 00 00 00 55 AA  <- magic .... 00000FFFF0: 00 00 00 00 00 00 00 00 │ 00 00 00 00 00 00 00 00 0000100000: EB 52 90 4E 54 46 53 20 │ 20 20 20 00 02 08 00 00  <- NTFS        The partition is of type 07, so it's NTFS, starts at sector 2048, and actually the filesystem is still there - at offset 0x100000 (2048*512 sector size) a nice NTFS system starts. So it seems all to be there.  From the looks of it, I'd expect Windows to see the disk as an NTFS partition and maybe require a filesystem check - not see it as not formatted at all.  Does that mean that the disk is readable and fine, but somehow Windows can't access it? Or did Windows cache the MBR (as I have not rebooted the machine yet)? Or maybe I don't even need an MBR, since this is not a bootable drive, merely an external USB storage unit?  What should I do to make Windows recognize the NTFS partition, if it's all there, intact and apparently healthy enough to be read without sector-by-sector recovery passes? Should I let chkdsk H: /f run and maybe try to fix it? (I haven't tried yet, as I heard chkdsk destroys data in some fringe cases)  (This is not a generic "how do I recover my data?" question, recovery wasn't that big of an issue in this case, as there was no unique data on that disk - it's more of a "what's missing, why doesn't it work, can it be fixed instead of recovered?" question. Most "RAW partition" trouble reports involve CHKDSK refusing to operate on a RAW partition; here, CHKDSK works fine, oddly enough.)

What steps can I take to try to recover lost or inaccessible data from any storage device?  Answers:   This applies to any computer storage device, e.g. internal/external hard drives, USB sticks, flash memory. The most important thing is to STOP using it, any type of I/O can ruin your chances of a recovery.     We have separate questions covering common problems with USB flash drives in greater detail:


Let $X$ and $Y$ be mean 0 and variance 1 random variables such that we choose $\alpha$ and $\beta$ to minimise  $$\mathbb{E}(X-\beta Y)^2$$  and   $$\mathbb{E}(Y-\alpha X)^2$$  after not so difficult derivation, I arrive at $\alpha = \mathbb{E}(XY)/\mathbb{E}X^2$ and $\beta = \mathbb{E}(XY)/\mathbb{E}Y^2$, so $\alpha = \beta$.   This seems very strange, because if $y=mx$ is regression line, then surely $x = \frac{1}{m }y$.

The Pearson correlation coefficient of x and y is the same, whether you compute pearson(x, y) or pearson(y, x). This suggests that doing a linear regression of y given x or x given y should be the same, but I don't think that's the case.   Can someone shed light on when the relationship is not symmetric, and how that relates to the Pearson correlation coefficient (which I always think of as summarizing the best fit line)?


I want to add to my document a kind of a border (actually I don't know how I should call it) that you can see below. It's probably helpful for  or .  This example comes from . How can I do it?

I'm working with the article document class:  \documentclass[a4paper, twoside, openleft, showtrims]{article}   I need to print a page that has color on the edges. The people who need to print this asked to add a 3mm on each page so they can cut it.  Solution (by Christian Hupfer) for the crop marks:   \usepackage[a4,frame,axes,cross,pdftex,center]{crop}


What is the proof of $n^2 = 1 + 3 + 5 + ... + (2\times n - 1)$?  While I verified that this is true for small numbers, I am looking for a mathematical proof for all Natural Numbers .

I'm new to induction so please bear with me. How can I prove using induction that, for each positive integer $n$, the sum of the first $n$ odd positive integers is $n^2$?  I think $9$ can be an example since the sum of the first $9$ positive odd numbers is $1,3,5,7,9,11,13,15,17 = 81 = 9^2$, but where do I go from here.


I have upgraded my mega ring, it's 8:15 and I can't find any mega stones. Is this a glitch? Will i have to restart my game, or buy a new one maybe? I've tried finding all of the stones on many occasions but to no avail. I'VE ALREADY UPGRADED MY MEGA RING AND ITS AFTER 8 AND BEFORE 9. Why is this happening?

I upgraded my Mega Ring and have been looking for Mega Stones, and I found . However, the Mega Stone isn't in the place it's supposed to be, and I'm sure the location is right. Why isn't my Mega Stone here?


I am running virtual server with Windows Server 2012 R2 for RDS purpose mostly. OpenVPN server is installed on this host as well. Firewall is configured in a way that RDP connections could only be made from VPN network. But now to access RDP users have to type server's VPN ip (like 10.8.0.1), instead of using friendly DNS name (I have a domain registered). What would be the simplest way to bind a hostname to this ip? Changing host's file on each client machine is obviously not an option. Thanks in advance.

I'm using OpenVPN through Tunnelblick on MacOS X Lion.  I need to set specific DNS (with local IP, which works only when VPN is up) for the duration of this VPN session only.  I do not have access to the OpenVPN server configuration. Only client config. Also, DNS from the server doesn't work.  So it works like this: I connect to VPN, go the Network preferences and manually set DNS. After VPN is disconnected, I switch back to default. It works, but it needs to be automatic.  After some exploration I found that OpenVPN up- and down- scripts might help me with that. Unfortunately, I haven't found any specific documentation about how exactly it can be done.  How it can or can't be done? Any advice would be appreciated!


I have already gone through the  in Unix & Linux and tried altering /etc/passwd manually like below  user1:x:1001:1001:,,,:/home/user1:/usr/sbin/nologin   after making change user1 is not being able to login from terminal but surprisingly can login from gnome   What's wrong?  Description:    Ubuntu 14.04.3 LTS kernel:         3.19.0-33-generic

Well I know the question is weird, but i have a user "Bob" and I want only bob's account to be stuck in infinite login loop. Please note I don't want to get out of a login loop..I want this particular user to be stuck in infinite login loop.   How do I do this?


I have 3 2D points: the start, the middle and the end. I need to calculate parabola passing over these points where the middle one is its vertex (kind of a smooth route over them). I know about a simple 3 linear equations but I don't know how to constraint the middle point to be the vertex.

I'm looking for a possibly rotated parabola in the plane, i.e., the solution to a quadric like $$ Ax^2 + 2Bxy + Cy^2 + Dx + Ey + F = 0 $$ where exactly one of the eigenvalues of  $$ \begin{bmatrix} A & B \\ B & C \end{bmatrix} $$ is zero, and where the solution set is nonempty.   I know the $xy$ coordinates of the vertex $V$ of the parabola (i.e., the point that lies on the axis of reflectional symmetry) and of two points $P$ and $Q$ of the parabola, one on each side of the vertex, so that going from $P$ to $V$ to $Q$ along the parabola involves no backtracking.   (The corresponding problem where $P$ and $Q$ might both be on the same side has multiple solutions for some configurations, but that's why I've included the "between-ness condition".)   I'd like to know either the coefficients $A, \ldots, F$, or the focus and directrix, or any other unambiguous description of the parabola that I can convert to one of these.   I keep feeling as if something from projective geometry involving perspectivities and projectivities and (2,2)-correspondences ought to make this simple, but I can't see it.


I installed Windows 10 and ubundu 18.4 in Lenovo V530s Intel 9th Gen Core i3 Tower Desktop .After installation I restarted but only opening windows 10.Grub menu does not display.I installed in UEFI mode.What change do  make in Bios to display grub menu. Please help me

I installed Ubuntu on a Dell XPS 13 laptop that had Windows 10 preinstalled on it. I installed it from a USB flash drive on a partition. When I boot my computer I can only boot into Windows 10 and Ubuntu is nowhere to be seen.  If I boot into my USB then I can see that Ubuntu is installed, but I can't get to it from the BIOS boot menu.


Solve this recurrence relation by generating its direct   formula: $$a_n = 3a_{n-1} + 2n, a_0 = 1$$   Using the direct formula find the   $10th$ term of this recurrence relation.    My answer:  $a_{10} = 147601$   Is this correct?

Solve the following recurrence relation by generating its direct   formula: $$a_n = 3a_{n-1} + 2n, a_0 = 1$$   Use the direct formula to find the   $10th$ term of the recurrence relation.    My attempt:  $3(10-1) + 2(10)$  $3(9) +  20$  $27 + 20$  $10th$ term = $47$  Is this correct?


Assume we toss a coin 10 times, independent of each other.  Each time we can get Heads (H) or Tails (T) , regardless of whether it is fair or not.  So for example this is one possible outcome: HHHHHHHHHH ie 10 heads. Let's call this a 10-toss sequence.   The total number of possible 10-toss sequences is 2^10 because each toss has 2 possible outcomes: Heads or Tails.  --The first question is What is the meaning of 10!/(3!7!) ? The answer is that It is the total number of ways, by which we can place the three heads inside the 10-toss sequence. The order by which we place the three heads does not matter.   --The second question is : What is the total number of possible 3-head sequences? Is it 10!/(3!7!)? Some say YES. Others, say NO. A 10-toss sequence with three heads, can be this one: HHH THTHTHT. So three positions are fixed to 'heads'. The remaining seven positions can be H or T. So we have 2^7 possible 7-toss sequences. And the three heads can be anywhere in this 10-toss sequence.   So an answer can be that the total number of 10-toss sequences with 3 heads is 10!/(3!7!) multiplied by (2^7) . That is in the 10-toss sequence the number of ways by which we can place 3 heads is 10!/(3!7!). Then, we have to say something about the remaining 7-toss sequence. Each position can take Heads or Tails . So 2^7 is the possible number of this 7-toss sequence.   However, I know that the correct answer is 10!/(3!7!) and that we don't need to multiply by 2^7. But I cannot understand why.

This is a question that has received various answers. This questions seems simple, but it proves to be rather tricky.  So :  We flip a coin (H-T) independently $10$ times. Let's for the moment not care about whether it is fair or not.   How many $3$-head sequences are there?  Solution:  Some say that the answer is $\displaystyle\frac{10!}{7!3!}$, but this is the number of ways  by which $3$ heads can be arranged in $10$ positions. This answer , however, does not say anything about the remaining $7$ positions.   Each of these seven positions can be H or T. The total number of $7$-element sequences is $1\cdot1\cdot1\cdot2^7=2^7$. Then we have to multiply this by $\displaystyle\frac{10!}{7!3!}$ as the three heads can be anywhere. But I have found that this is not the correct answer. The correct is just $\displaystyle\frac{10!}{7!3!}$. So why not multiply by $2^7$?


How to read characters printed on a process's own control terminal ? Or is this even possible under Linux ?  My program needs to launch an SSH client and start a password authenticated session (C/C++ programming language), so injecting the password into the SSH client's control terminal is required. Since the SSH client and my program share the same control terminal, password injection can be achieved through system call (man tty_ioctl):  ioctl(STDIN_FILENO, TIOCSTI, password)   However the injecting must be at the right time, if password injected too early, the injected data will be ignored, so my program has to wait for the password prompt "foobar's password:" before injecting password. Currently my solution is to wait a few seconds before the injection, which is very unreliable.  So what is right time to inject the password into the control terminal ?  I don't want to create a new pseudo-terminal, too many terminal related things have to be handled.

I've got a utility that outputs a list of files required by a game.  How can I run that utility within a C program and grab its output so I can act on it within the same program? UPDATE: Good call on the lack of information.  The utility spits out a series of strings, and this is supposed to be portable across Mac/Windows/Linux.  Please note, I'm looking for a programmatic way to execute the utility and retain its output (which goes to stdout).


I am trying to override the functionality of 'required' and 'minlength' validators provided by jQuery Validator plugin. Following is my code:  jQuery(".form-cls").validate({              errorElement: "span",              errorClass: "error-msg",         rules: {             email:{                 required:true,                 email:true,                 alreadyExistEmail: true             },             user_email:{                 required:true,                 email:true             },             password:{                 required: function (element) {                                     return checkIfPasswordIsRequired();                                 },                                 minlength: function (element) {                                   return passwordLengthCheck(element);                                   }                     }         }     });  function checkIfPasswordIsRequired()     {         if(jQuery("#facebook_id").length > 0 || jQuery("#linkedin_id").length > 0 || jQuery("#xing_id").length > 0) {             if(jQuery("#facebook_id").val() != "" || jQuery("#linkedin_id").val() != "" || jQuery("#xing_id").val() != "") {                 return false;             }         }         return true;     }      function passwordLengthCheck(element)     {         if(element.value.length < 6)         {           return false;         }         else         {           return true;         }     }   Now here the first check on password field is working fine that is of 'required' but the second check is not working. If have checked it my console.log(element.value.length) and it gives the length of value in password field each time the value is changed/altered but depending on the condition in function passwordLengthCheck it never shows/displays error. Kindly help!!

How do you create a simple, custom rule using the jQuery Validate plugin (using ) that doesn't use a regex?  For example, what function would create a rule that validates only if at least one of a group of checkboxes is checked?


Let $M(m,n,r)$ be the matrix space of real matrices $m\times n$ with $rank \leq r$.  Is $M(m,n,r)$ an open set? or closed set? or Does it have some property?  Regards

Let $M$ be the space of all $m\times n$ matrices. And $C=\{X\in M|\operatorname{rank}(X)\leq k\}$ where  $k\leq \min\{m,n\}$. Check whether the set $C$  is:   Closed Connected Compact Open   What are some other good properties of the set $C$,for example is it a manifold?  Clearly the set $C$ is closed  if someone is interested  a good proof can be found , hence $C$ is not open. Also as $C$ is unbounded therefore not compact. How to check whether the set $C$ is connected or not?


I'm new to blender and imported this mesh of a monitor and wall mount. The monitor appears to have an armature attached to it but bone as far as I can tell no bones. It does have these blue lines around the mesh in edit mode. Can someone tell me what these are? Are they a part of the armature? I should be able to swivel the monitor in the obvious points. I know this exact model was used to swivel the monitor before in a different program but how can I make it work here? Also, side question, In object mode this mesh has a light blue color and the screen has a light orange color. Some other objects I imported have seemingly random colors. Can someone tell me what these are?

There are red and pink edges on my mesh.  What do these colored edges mean? How can I use them?


I have an Android 4.4.2 phone and I enabled ART instead of Dalvik.  When I go to the Google Play Store and try to install Facebook, it can't install the app.  I get two errors, sometimes I get     Invalid installation package   and sometimes     Error -24   Is there a way to know what's going on?

I just updated my Moto X to latest and greatest Android 4.4 KitKat (I even did full factory reset just to be sure) and now I'm trying to install  but unable to do so, I'm getting following error:     Unknown error code during application install "-24"   Please advise.


Hint: Consider the functions f(z)+g(z) and f(z)-g(z).

is it true if $f,\overline f$ are both analytic in a domain $\Omega$ then $f$ is constant? I am not able to  find out what property of holomorphic map I need to apply. please help.Thank you.  $f(z)=u(x,y)+iv(x,y)$, $\bar{f}(z)=u(x,y)-iv(x,y)$


Can anyone give me the pattern of the regex to get all the local images ONLY. :( I'm using the code below but it includes the image links.    Regex rgx = new Regex("[^\\/:*?\"<>|]+\\.(?i)(jpg|png|gif|bmp)", RegexOptions.IgnoreCase);   input:   http://dl9.glitter-graphics.net/pub/846/846279rr8zhg26y6.gif  images/strawberries.jpg   output:   846279rr8zhg26y6.gif  strawberries.jpg    I don't want the 846279rr8zhg26y6.gif

It seems like every question on stackoverflow where the asker is using regex to grab some information from HTML will inevitably have an "answer" that says not to use regex to parse HTML.  Why not? I'm aware that there are quote-unquote "real" HTML parsers out there like , and I'm sure they're powerful and useful, but if you're just doing something simple, quick, or dirty, then why bother using something so complicated when a few regex statements will work just fine?  Moreover, is there just something fundamental that I don't understand about regex that makes them a bad choice for parsing in general?


This lines are found in discussion section of Alexnet's Paper.  Our results show that a large, deep convolutional neural network is capable of achieving recordbreaking results on a highly challenging dataset using purely supervised learning. It is notable that our network’s performance degrades if a single convolutional layer is removed. For example, removing any of the middle layers results in a loss of about 2% for the top-1 performance of the network. So the depth really is important for achieving our results.  I would like to know why adding or removing layers fails the convnet.

In recent years, convolutional neural networks (or perhaps deep neural networks in general) have become deeper and deeper, with state-of-the-art networks going from 7 layers () to 1000 layers ( in the space of 4 years. The reason behind the boost in performance from a deeper network, is that a more complex, non-linear function can be learned. Given sufficient training data, this enables the networks to more easily discriminate between different classes.  However, the trend seems to not have followed with the number of parameters in each layer. For example, the number of feature maps in the convolutional layers, or the number of nodes in the fully-connected layers, has remained roughly the same and is still relatively small in magnitude, despite the large increase in the number of layers. From my intuition though, it would seem that increasing the number of parameters per layer would give each layer a richer source of data from which to learn its non-linear function; but this idea seems to have been overlooked in favour of simply adding more layers, each with a small number of parameters.  So whilst networks have become "deeper", they have not become "wider". Why is this?


Suppose someone makes statements like these:  I like tasty food. I like beautiful pictures. I like well-written dramas / novels / articles / et cetera. I like good music.  As you see all those adjectives say something positive, yet entirely subjective, about the nouns the person likes. You might even say the adjectives are redundant, for example nobody likes food that's not tasty, but it depends on the person what type of food they'd call tasty. Is there a term for this type of statement? An example sentence:  These statements are ____, you should avoid them on your writing exams!  I found  where the adjectives describe a property that's already implied by the noun (a pleonasm). That's not the case here because you can say: "that food is very tasty", which isn't a pleonasm, nor is it otherwise redundant. Although when describing what you like by saying: "I like tasty food" it comes across as saying "I like food that I find tasty", in which the "that I find tasty" part is already implied by the "I like" part. After reading the Wikipedia page on pleonasms, I think my examples are pleonasms because the adjectives in bold are redundant in the context of the sentence. I am, however, looking for a more specific word (or subclass of pleonasms for that matter), it should at least imply that it's a pleonasm in the specific context (and not generally). A bonus would be if the term is specific to the verb adjective combination.

Consider this conversation:      John: I am giving free chess lessons.   Mary: Nice! You’re a true teacher.   John: How so?   Mary: A true teacher imparts knowledge without a price tag.   John: But what if teaching is his only source of income? Would he not be a “true” teacher then?   Mark (in response to the question above): You clearly mentioned “free chess lesson”.   I don’t see how Mark’s comment adds anything to the discussion or makes sense in the current discussion. It is “redundant” — that’s one word for it — but is there a more fitting word?


We in see in end of Game of Thrones that Jon Snow has to go to Castle Black as part of his punishment for killing Daenerys. But then he goes with the wildlings beyond the wall. Why did he go with them and not stay at Castle Black?

At the end of S08E06 of Game of Thrones, Jon Snow along with Tormund and others of the Night's Watch      leave the Night's Watch.   and go into the woods.  Where are they going? And why?


I play Minecraft of the xbox 360, but my friend plays Minecraft Java edition on pc. We want to figure out how to friend each other. I’ve already friended him by typing in his gamer tag. His account did show up and it is pending. Somehow he didn’t get it. We tried to figure out how he can accept my friend request but he couldn’t find it. Then we decided to try me joining his server except I can’t do that since I’m on the xbox 360. We just need to know how we can friend each other so we can cross-play on the same world/server.

Can players on a PC and an Xbox play together in any way? I.e. can Xbox users connect to a (modfied?) PC server, or vice versa?


If in a group $G$, $(ab)^3=a^3 b^3$ for all $a,b\in G$, amd the $3$ does not divide $o(G)$, prove that $G$ is abelian.  I interpreted the fact that $3$ does not divide $o(G)$ as saying $(ab)^3\neq e$, where $e$ is the identity of the group.   As for proving $ab=ba$, I did not get anywhere useful. I got the relation $(ba)^2=a^2 b^2$, but could not proceed beyond that. I got a lot of other relations too which I could not exploit- like $a^2 b^3=b^3 a^2$  A helpful hint instead of a solution would be great!  Thanks in advance!

The problem is:  If $G$ is a finite group with order not divisible by 3, and $(ab)^3=a^3b^3$ for all $a,b\in G$, then show that $G$ is abelian.  I have been trying this for a long time but not been able to make any progress. The only thing that I can think of is: $$ab\cdot ab\cdot ab=aaa\cdot bbb\implies(ba)^2=a^2b^2=aabb=(\text{TPT})abba.$$ Now, how can I prove the last equality? If I write $aabb=abb^{-1}abb$, then in order for the hypothesis to be correct, $b^{-1}abb=ba\implies ab^2=b^2a$. Where am I going wrong? What should I do?


How to find an argument of this complex number?   $$ z=1-e^{i\varphi}=1-\cos\varphi-i\sin\varphi $$   I know I should try to make $z$ equal to $r(\cos\psi+i\sin\psi)$. And then $Arg(z)=\psi$. But I don't really understand how to do that. I tried something like that: $$ z=2\sin^2\frac{\varphi}{2}-2i\sin\frac{\varphi}{2}\cos\frac{\varphi}{2}=2\sin\frac{\varphi}{2}\left(\sin\frac{\varphi}{2}-i\cos\frac{\varphi}{2}\right) $$ But obviously it didn't help much.

So the complex number z is given as   $z=1-cos(2\theta)-isin(2\theta)$  And the question is to find the argument of z in terms of $\theta$.   So, I used the formula for calculating the argument of a complex number:  $arg(z)=arctan (\frac{sin(2\theta)}{1-cos(2\theta)})$  $=arctan (\frac{2sin\theta cos\theta}{1-(1-2sin^2\theta)})$  $=arctan (\frac{2sin\theta cos\theta}{2sin^2\theta})$  $=arctan (\frac{cos\theta}{sin\theta})$  $=arctan (cot\theta)$  $=arctan (tan(\frac{\pi}{2}-\theta))$  $=\frac{\pi}{2}-\theta$  But apparently the answer is $\theta-\frac{\pi}{2}$.  Where might have I gone wrong?  Edit: the domain given in the question for $\theta$ was $0≤\theta≤\pi$


Do we need axiom of choice for all the theorems studied in basic courses like calculus 1 and linear albgebra? could we build this theory just by using ZF axioms?

I thought many results in calculus need axiom choice. For example, I thought one needs AC to prove that a bounded sequence in the real line has a convergent subsequence. Recently I was taught that one only needs mathematical induction to prove it. So here are my questions.  Can most results in calculus be proved without AC? If yes, what are the exceptions, to name a few?  Obviously a theorem which uses Zorn's lemma most likely does need AC. So please exclude obvious ones.  Edit By "without AC", I mean without any form of AC, i.e. countable or not, dependent or not. In other words, within ZF.  Edit One of the motivations of my question is as follows. People often unconciously use AC to prove theorems. And it often turns out that their uses of AC are unnecessary. For example, an infinite subset of a compact metric space has a limit point. In his book "Principles of mathematical analysis", Rudin proves this by choosing a suitable neighborhood of every point of the space. He uses AC here, though he doesn't say so. However, since a compact metric space is separable, you can avoid AC to prove this theorem.  Edit I'll make the above statement clearer. You can even avoid countable AC to prove the above theorem. In other words, you can prove it within ZF.  Edit I'll make my questions clearer and more specific. By calculus, I mean classical analysis in Euclidean spaces. Take, for example, Rudin's "Principles of mathematical analysis". Can all the results in this book be proved within ZF? If not, what are the exceptions?


If $y= \dfrac1{1+x} + \dfrac2{1+x^2} + \dfrac4{1+x^4} + \dots + \dfrac{2^n}{1+x^{2^n}} $, then find $\dfrac{\mathrm dy}{\mathrm dx}$.  I am stuck up in this question. I tried taking log on both sides and generate some simplified expression but was unable to do so. Any help would be highly appreciated. thanks

$\displaystyle\sum_{i=0}^n \frac{2^i}{1+x^{2^{i}}}$  What technique is applicable here? I can't find a way to manipulate this sum to make it telescope. Just guide me.


After updating my computer to 19.10 Kubuntu sound is unusable.  It switches it to monitors the soundcard and sets it to default. nothing seems to work. Before the update setting it off worked.  Swiched off    It switches HDMI on    And sets it default

Each time I reboot Ubuntu 19.10, I have to open gnome-control-center and set the sound output device back to my Laptop's Built-in speakers. Otherwise, it will typically default to DisplayPort devices that don't even have speakers.    Which file are these settings saved to? I'm thinking that maybe that file is corrupted and that if I delete that file maybe Ubuntu 19.10 will start remembering my sound output preferences. I'm also open to other suggestions.


Yesterday I wanted to update my 16.04 Xubuntu. When I ran sudo apt update && sudo apt upgrade (system wasn't able to complete the upgrade process), the system froze and I had to restart by force.  But now I cannot even start the system anymore. After each reboot, only the grub terminal is shown. I also cannot access the grub menu by pressing ESC key (my system is UEFI).  Do you have any suggestion how to fix this?

This keep happening when I install the Ubuntu as a dual boot for my laptop. I get a black that appears when booting with the following messages.  Minimal BASH-like line editing is supported.    For the first word, TAB lists possible command completions.  Anywhere else TAB lists possible device or file completions.     grub>   grub>   grub>   grub>   grub>   grub>   grub>   grub>   grub>    I have to enter these commands like this:  grub> set prefix=(hd0,msdos6)/boot/grub/  grub> insmod normal  grub> normal   And the GRUB menu appears. How to make my GRUB menu appear without having to type those command at my GRUB prompts?  I tried sudo grub-install and it give me this error message.    I tried to check if i have chosen the right disk, which come two possibilities, /dev/sda1 and /dev/sda6, but neither of these two works, and they gave the same error message.  /dev/sda1/    /dev/sda6


I am running a fresh install of Ubuntu 14.04. I just downloaded the latest version of steam install files.  When running install a terminal is opened and the following text is output to the terminal:  ............... Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help resolve the situation:  The following packages have unmet dependencies:  libgl1-mesa-glx:i386 : Depends: libglapi-mesa:i386 (= 10.1.3-0ubuntu0.6)  unity-control-center : Depends: libcheese-gtk23 (>= 3.4.0) but it is not going to be installed                         Depends: libcheese7 (>= 3.0.1) but it is not going to be installed E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages. Press return to continue:    then I get and error that says  You are missing the following 32-bit libraries, and Steam may not run: libGL.so.1   I have tried all sorts of googled solutions like getting packages and updating my steam.conf file.  EDIT: I should mention that I have not installed nvidia drivers for my gt 710. I just used the existing ones that are auto installed by Ubuntu. Could these be insufficient?

I am not sure what caused this error, but here is what the whole error says, and also this is sitting as a notification, and preventing me from updating any software using Update Manager - Please provide some assistance or tell me how to figure out what to do to fix it.  Could not calculate the upgrade  An unresolvable problem occurred while calculating the upgrade.  Please report this bug against the 'update-manager' package and include the following error message: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'


I try to solve the following:     let $G$ be a simple graph with minimum degree of $\frac{(n-1)}{2}$ with $n$ vertices. prove that $G$ is connected and that the diameter of $G$ is at most $2$   I Know how to prove that the graph is connected -      assume that we take some connected component K, for each $v\in k$ we have that $deg(v)=\frac{n-1}{2}$ so that means that we have at least $\frac{n-1}{2}+1=\frac{n+1}{2}$ vertices which implies that if we have more then one connected component we have more than $n$ vertices - a contradiction   But  how to prove the diameter part? my way of thinking was to compute how many vertices can I reach after "two moves" trail but I got some not conclusive result:  $$\frac{n-1}{2} + \frac{n-1}{2}\cdot ( \frac{n-1}{2} -1)$$ $$\Downarrow$$  $$=\frac{(n-1)^2}{4}$$ which is not bigger than $n-1$ for all $n$ I know how to work around this but this seems "lame" I am sure there is some other elegant way.

Let $G$ be a graph of order $n \geq 3$ such that $\delta (G) \geq \frac{n-1}{2}.$ Determine the diameter of $G$.   So $\delta (G)$ is the minimum degree of a vertex in the graph $G$. How can I approach such a question? I know that the diameter of a graph is the "largest shortest-path" between any pair of vertices in a graph, or in other words, the maximum distance between all possible pairs of vertices in $G$. Also, do I have to make use of the maximum degree of $G$ to solve this problem?


Prove the set $K = \{\frac{1}{n} \mid n\in \mathbb{N}\}\cup \{0\}$ is compact.  I have tried to write a proof for this fact. Please critique it.   Proof.  Let $\mathcal{G} = \{G_\alpha \mid \alpha \in A\}$ be any open cover for $K$. Since $\mathcal{G}$ is an open cover, we have $K\subseteq \bigcup_{\alpha\in A}{G_\alpha}$. Hence, $0\in K$ implies that there exists some $G_0 \in \mathcal{G}$ such that $0\in G_0$. Since $G_0$ is open, there exists $r>0$ such that $B_r(0) \subseteq G_0$. We know from previous results that $\frac{1}{n} \to 0$. Hence, $B_r(0)$ contains all but finitely many terms of $\frac{1}{n}$ and consequently, $G_0$ contains all but finitely many of these points. Let $N$ be such that $\frac{1}{n} \in G_0$ for all $n\geq N$. Then for each point $1,\frac{1}{2},\dots,\frac{1}{N-1}$ we can choose a corresponding open set $G_1,G_2,\dots,G_{N-1} \in \mathcal{G}$ that contains each point. Hence, $\{G_0,G_1,G_2,\dots\,G_{N-1}\}$ is a finite subcover for $K$.

Let $D=\{ \frac{1}{n} \mid n\in\mathbb{N} \} \cup\{0\} \subset \mathbb{E}^1$. Prove that $D$ is compact.      Proof: It is clear that $D$ is bounded above by $1$ and bounded below by $0$. We need to show that the set $D$ is closed, or it   contains all of its limit points. The only limit point of the set $D$   is $0$. But since $D$ includes $0$, $D$ must be closed. Hence, $D$ is compact because it is closed and bounded.  $\blacksquare$   I claimed that $0$ is the only limit point of the set $D$ but is this okay? I stated it allegedly without giving much reasoning but I thought it was very obvious from looking at the set.   Can $D$ be its own open cover? If so, can I just give an example of finite subcover of $D$ to show that it is compact? For example, since $(2,0) \cup (0,2)$ covers $D$, $D$ is compact.


I noticed that when I am on the generic Stack Exchange page, the one that is linked to by clicking the button furthest left on the top bar, and then I click on that button again to access the drop-down.  The icons for established SE sites are showing up as a generic black icon with lettering. This is in contrast to the dropdown on the farthest right of the top bar, which displays the site icons for each site.  Perhaps this is status-by-design, but it seems to me that the two dropdowns should have consistent icon usage to avoid confusion.  Here are screenshots of both dropdowns, first the one from the top left button that shows the black icons, and then the top right button that shows the normal site icons.  Black lettering icons:    Normal icons that I'm used to:

I just checked my (meagre) achievements for today on  and got this:    Where as it should look like this:    The site icons are a bit awry.


I have a header div and a div underneath it. I need the div underneath the header div to adjust depending on the height of the browser window size.   In CSS, when I add height:100% it creates a scroll bar at the side of the page. When I adjust the percentage of the width, spacing at the bottom of the page constantly changes because it is done with percentages.   I would like the div below the header to always adjust with the window size in height with no spacing at the bottom.  How do I do this?  Here is the Fiddle   I am not sure why but in JSFiddle the bottom div is not extending height: 100%  here is the code: HTML
   Header

   Bottom Div
   CSS  .main { width:100%; height:60px; border: solid; }  .left { height: 100%; width: 300px; border:solid; }

I am working on a web application where I want the content to fill the height of the entire screen.  The page has a header, which contains a logo, and account information. This could be an arbitrary height. I want the content div to fill the rest of the page to the bottom.  I have a header div and a content div. At the moment I am using a table for the layout like so:  CSS and HTML    #page {     height: 100%; width: 100% }  #tdcontent {     height: 100%; }  #content {     overflow: auto; /* or overflow: hidden; */ }

...

...

     The entire height of the page is filled, and no scrolling is required.  For anything inside the content div, setting top: 0; will put it right underneath the header. Sometimes the content will be a real table, with its height set to 100%. Putting header inside content will not allow this to work.  Is there a way to achieve the same effect without using the table?  Update:  Elements inside the content div will have heights set to percentages as well. So something at 100% inside the div will fill it to the bottom. As will two elements at 50%.  Update 2:  For instance, if the header takes up 20% of the screen's height, a table specified at 50% inside #content would take up 40% of the screen space. So far, wrapping the entire thing in a table is the only thing that works.


I have Ubuntu 11.04 installed on my computer alongside Windows 7.  Is it possible to also dual-boot 12.04?  If not, will I need to overwrite the previous version of Ubuntu?. If so how can I do it?

I have Ubuntu 10.10 32 bit already installed on my machine..I am using MongoDB and it does not work properly with 32 bit machine.  So I want to install 64 bit Ubuntu 10.10 on my system on another partition (so that I can have both 32 bit and 64 bit versions).  Is it okay to install both 32 bit and 64 bit? I mean will it give any problems? On which partition should I install the 64 bit version? My partitions are as follows:  Filesystem            Size  Used Avail Use% Mounted on /dev/sda1              37G   11G   25G  30% / none                  1.4G  260K  1.4G   1% /dev none                  1.4G  776K  1.4G   1% /dev/shm none                  1.4G  244K  1.4G   1% /var/run none                  1.4G     0  1.4G   0% /var/lock /dev/sda6             129G   73G   50G  60% /home /dev/sda7             127G   76G   45G  64% /vol   Waiting for your replies.


I have notepad++ on windows and I am about to download Ubuntu but I am wondering if there's a special version for Ubuntu or can I just use the one I have now. If it there's no version for Ubuntu, Can anybody please recommend a similar program? By the way sorry for the tags. I need more reputation to create a new tag, that's the closest i could i get

I use  on Windows 7 and I want to know if there is a good substitution for it on Ubuntu.   I want something that is good for editing html files.


(First time using Ubuntu) I have installed Ubuntu 16.04 LTS on 16GB USB.  With the command lspci , I found that I have Network controller: MEDIATEK Corp. MT7630e 802.11bgn Wireless Network Adapter on my HP Pavilion 15-n004tx Notebook PC.  It was not shown in the network drop-down list from Menu bar.  After using the instructions from  , now MEDIATEK MT7630 is shown in network list, but disconnected.  Can this adapter be used on my laptop. If yes, what else should I do to make it work ?  I am using a USB wifi adapter for now. But if I remove this USB wifi adapter, the internal Wifi adapter (MEDIATEK MT7630) is not working.  lspci -knn | grep Net -A3; rfkill list  08:00.0 Network controller [0280]: MEDIATEK Corp. MT7630e 802.11bgn Wireless Network Adapter [14c3:7630]     DeviceName: Mediatek WLAN Mediatek Civic MT7630E bgn 1x1 + BT 4 LE PCIe+USB HMCWW     Subsystem: Hewlett-Packard Company MT7630e 802.11bgn Wireless Network Adapter [103c:197c]         Kernel driver in use: mt7630e     Kernel modules: mt7630e   0: hci0: Bluetooth     Soft blocked: no    Hard blocked: no  1: phy0: Wireless LAN     Soft blocked: no     Hard blocked: no   The MEDIATEK MT7630 adapter is present only if I connect a USB wifi adapter.  Why is MT7630 adapter depending on external USB wifi adapter ?    Edit : The solution given  works for me. Wifi is working now.

It worked with the pre-installed Ubuntu, but after re-installing Ubuntu dual-boot with Windows 8.1, the WiFi is not working.  Is there a driver for this adapter that will work on Ubuntu 12.04?


Are their any specific requirements for the IV when using Salsa20? Is it for example allowed to re-use the same IV when encrypting with the same session key? Should the IV be random? etc   I tried to find some information in the related Salsa20 paper, but I could not really find any mentions of specific Salsa20 IV requirements.  Thanks for the information :)

what is the source of nonce in SALSA20 algorithm.  basically who provides the value of nonce in SALSA20 algorithm


I am struggling to understand this proof. Suppose that $p$ is the smallest prime that divides $|G|$ show that any subgroup of index $p$ is normal in $G$. Proof Let $\phi \rightarrow S_p$ be the homomorphism given by the generalized Cayley theorem. We claim $ker(\phi)=H$ which implies $H$ is normal. By first isomorphism theorem $|G/Ker \phi|$ divides $|S_p|=p!$ON the other hand $|G/Ker \phi|$ divides $|G|$ by lagrange's theorem. Since $ker\phi \leq H$ and $p$ is the smallest prime factor of $|G|$, $ker\phi=H$. I am struggling to understand this if anyone could help explain this?

Generalizing the case $p=2$ we would like to know if the statement below is true.  Let $p$ the smallest prime dividing the order of $G$. If $H$ is a subgroup of $G$ with index $p$ then $H$ is normal.


I have a MATLAB program that generate many graphics in .png format in a folder Can I include in my document, with a LaTeX code, all photo of a specific folder?  I can include all graphics with a equal scale and 3 graphics for rows in my document?

I have a set of pictures in my working directory and I want to make a PDF report using these images. I want to include all of them, but the number of the pictures changes in each case. I would like to make a "for" loop to insert each picture one after the other sequentially. Can anyone help me? At the moment the code I have is the following:   \begin{figure}[h!] \begin{centering} \includegraphics[width=10cm,height=10cm]{Figure1.png} \caption[Sèries temporals de vent i direccions]{Sèries temporals velocitat de vent i     direccions. filtratge de pics i glaçades de velocitat.} \label{Serie} \end{centering}  \end{figure}   I would like to do it for every .png image in the directory. Thanks for your questions: I am using Windows 7 and the file names follow the pattern Figura1.png, Figura2.png and so forth. So which of these possibilities would fit best?


I have a terrible motherboard:  Manufacturer: Foxconn Model: 2AB1 Chipset: AMD 785G Southbridge: AMD SB700 Brand: American MegaTrends INC.  It wont let me overclock my CPU, so I've decided to upgrade it. I am going to get a motherboard with a socket AM3 and DDR3 RAM for my supplies that will let me overclock. Want I want to know is:   When I upgrade my motherboard, do I need to reinstall anything? Will I still have Windows 7 Premium? Will I need new drivers or anything such?

I need to replace my current motherboard with a new one, no other parts are changed.   Must I format my harddrive and reinstall windows, or can I use the old installation and let windows install the right drivers?  I realize, there might be a performance hit, but I'll probably need the new one just for a week and would like to replace it with the old motherboard again.


If I turn invisible and grapple a foe, does he still have disadvantage to hit me because I am invisible or does he now know where I am?

I was looking through the  when I noticed this:  When you make a Strength (Athletics) check to grapple or shove someone, are you making an attack roll? Again, the answer is no. That check is an ability check, so game effects tied to attack rolls don’t apply to it. Going back to an earlier question, the hex spell could be used to diminish a grappler’s effectiveness. And if the grappler’s target is under the effect of the Dodge action, that action doesn’t inhibit the grapple, since Dodge doesn’t affect ability checks.  I had always played that the 2nd-level invisibility spell would end on a grapple, since it counts as an attack, but this seemed to suggest otherwise. I researched this a bit and found  from December 2015, which seemed to suggest that it was indeed an attack roll:  Grappling/shoving an enemy does end the sanctuary spell on you, since you have made an attack.  My best guess is that you must take the Attack action to perform an ability check, as grappling in the PHB is called a “special melee attack” (PHB p. 195), although that doesn't make a huge amount of sense:  [...] you can use the Attack action to make a special melee attack, a grapple. [...]  Do these two answers by Crawford contradict each other? And should the invisibility spell end when a grapple is attempted? The description for the invisibility spell says:  A creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target's person. The spell ends for a target that attacks or casts a spell.


I have a content type with a custom view mode. How do I make sure node always get rendered with my custom view mode?  What would be the right way to programmatically change the node view mode before rendering?

In Drupal 7 I did something like:    function mymodule_views_pre_render(&$view) {     //dpm($view);     if ($view->name == 'services') {       $view->style_plugin->row_plugin->options['view_mode'] = variable_get('services_teaser');     }     else if ($view->name == 'portfolio') {       $view->style_plugin->row_plugin->options['view_mode'] = variable_get('portfolio_teaser');     }   }   I don't know how to set the view mode on the fly, in Drupal 8. The idea is to be able to select the view mode for the view from a configuration form, instead of doing it from the view form.  How do I achieve this?


In elementary calculus, a usual argument for the derivative not being defined at an endpoint is that one of the lateral derivatives not being defined. See for example  page 3. Central to the definition of the derivative is that of a limit.   $$\lim_{x\rightarrow a}f(x)=b \Leftrightarrow \forall_{\epsilon}\exists_{\delta}\forall_{x}(x\in D \ \land \ x\in N_{\delta}(a)\ \Rightarrow \ f(x) \in N_{\epsilon}(b) )$$  I fail to see why they say that for an endpoint the derivative is not defined, when clearly using this definition of limit we can speak of continuity at an endpoint... For the left endpoint of a closed interval, the left limit would be defined for any $b$, since the premiss of the implication is false, making the whole implication true for whatever b.

In Rudin's "Principles of Mathematical Analysis" he defines the limit of a function as follows.     Let $X$ and $Y$ be metric spaces; suppose $E \subset X$, $f$ maps $E$ into $Y$, and $p$ is a limit point of $E$.  Then   $$ \lim_{x \to p} f(x) = q $$   if there is a point $q \in Y$ with the following property: For every $\epsilon > 0$ there exists a $\delta > 0$ such that   $$ d_Y(f(x),q) < \epsilon $$   for all points $x \in E$ for which   $$ 0 < d_X(x,p) < \delta. $$   The functions $d_X$ and $d_Y$ are the metrics on $X$ and $Y$, respectively.  He then defines the derivative of a real function as follows.     Let $f$ be defined on $[a,b]$.  For any $x \in [a,b]$ form the quotient   $$ \phi(t) = \frac{f(t) - f(x)}{t - x} \qquad a < t < b,\, t \neq x, $$   and define   $$ f^\prime(x) = \lim_{t \to x}\, \phi(t), \qquad (1) $$   provided this limit exists in accordance with [the above definition].  We thus associate with the function $f$ a function $f^\prime$ whose domain is the set of points $x$ at which the limit (1) exists.   I can't reconcile what's wrong with derivatives at endpoints.  As a concrete example, let $f: [0,1] \to \mathbb{R}$ be defined by $f(x) = x^2$.  I claim that $f^\prime(0) = 0$.  Indeed, the difference quotient is $$ \phi(t) = \frac{t^2 - 0^2}{t - 0} = t $$ and so we need to show $$ \lim_{t \to 0}\, t = 0. $$ Let $\epsilon > 0$ and choose $\delta = \epsilon$.  Then for all $t \in [0,1]$ such that $0 < |t| < \delta$ we have $|t| < \epsilon$.  Hence $f^\prime(0) = 0$, even though it is at an endpoint of the domain of $f$.  In particular, there's no use to introduce one-sided derivatives.  Am I missing something?


The types I am talking about are shown on page 3 here:   int8_t uint8_t int16_t uint16_t int32_t uint32_t int64_t uint64_t  I am using Visual Studio 2012.  If it's different for GNU/Mingw include how to get them on those compilers too.

To my amazement I just discovered that the C99 stdint.h is missing from MS Visual Studio 2003 upwards.  I'm sure they have their reasons, but does anyone know where I can download a copy?  Without this header I have no definitions for useful types such as uint32_t, etc.


Prove that if $|a_1\sin x+a_2\sin2x+a_3\sin3x+\cdots+a_n\sin nx|\leq|\sin x|$ for $x\in R,$then $|a_1+2a_2+3a_3+\cdots+na_n|\leq1$  When we try to differentiate it on both sides wrt $x$,then modulus sign comes,how will one prove this question?Please help me.

Let $f\colon\mathbb R\to\mathbb R$ defined by  $$f(x)=a_1\sin x+a_2\sin2x+a_3\sin3x+\cdots+a_n\sin nx,$$ for some values $a_1,a_2,a_3,\cdots,a_n\in\mathbb R.$ Prove that $$ |f(x)|\le|\sin x|\quad \forall x\in \mathbb{R}$$ implies: $$|a_1+2a_2+3a_3+\cdots+na_n|\le1$$


I understand that [ didn't = did not].  But is it correct to write the following?     Why didn't he come to work?   Why did not he come to work?   And can it be written as follows?     Why he didn't come to work?   Why he did not come to work?    Are both ways correct? Kindly explain a little.

I was wondering which one is grammatically correct between "Why didn't (or did not) somebody do something?" and "Why did somebody not do something?"


I'm trying to write a shell script in RHEL which will execute grub-md5-crypt and the user will type their password.  Now the problem is how can I grab the encrypted md5 hash displayed to the user in the shell script?  I tried to figure this out but command redirection will not work here.  So how can I get the md5 encrypted text in the shell script after the script has executed grub-md5-crypt?

I have an operation using cut that I would like to assign result to a variable  var4=echo ztemp.xml |cut -f1 -d '.'   I get the error:     ztemp.xml is not a command   The value of var4 never gets assigned; I'm trying to assign it the output of:  echo ztemp.xml | cut -f1 -d '.'   How can I do that?


I know that in ZFC, we can always compare the cardinality of two sets, because every set is equipotent to some ordinal. But without AC, can we say that for two sets $x$ and $y$, either there exists an injection from $x$ to $y$ or an injection from $y$ to $x$?

If, for any two sets $A$ and $B$, Either $|A|<|B|, |B|<|A|$ or $|A|=|B|$ holds, does the axiom of choice holds? Why?


How can I diagnose random freezing on Ubuntu? I've tried fresh reinstalls several times but the OS still freezes often.

All operating systems freeze sometimes, and Ubuntu is no exception. What should I do to regain control when...   just one program stops responding? nothing at all responds to mouse clicks or key presses? the mouse stops moving entirely? I have an    In what order should I try various solutions before deciding to pull the power plug?  What should I do when starting up Ubuntu fails?  Is there a diagnostic procedure I can follow?


I have a problem with sending mail from php code. I want to use polish characters in email message. I searched many post on stack with the same problem but nothing works.  <?php if(isset($_POST['submit'])){  $to = "...@gmail.com";  $from = $_POST['email'];  $name = $_POST['name'];  $phone = $_POST['phone'];  $subject = "Wiadomość ze strony";  $message = "Imię i Nazwisko: " . $name . "\nTelefon kontaktowy: " . $phone . "\n\nTreść wiadomości:" . "\n\n" . $_POST['msg'];   $headers = "From: $from \r\n".              "MIME-Version: 1.0" . "\r\n" .              "Content-type: text/html; charset=UTF-8" . "\r\n";   mail($to,$subject,$message,$headers);  header('Location: index.html'); } ?>   I have asked my friend to check on his vps and this code work correctly. So there must be a problem with server. I use linuxpl.com.  I found the solution. Polish characters work fine when I added this line in html form.  accept-charset="ISO-8859-1"

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.


Compute: $$I(y)=\int_0^{\frac {\pi}2} \ln(\cos^2x+y^2\sin^2x) dx$$  So$$I'(y)=\int_0^{\frac {\pi}2}\frac {2y\sin^2x}{\cos^2x+y^2\sin^2x}dx$$ Now what?

I'm trying to calculate this integral: $$ \int_{0}^{\pi/2} \ln(a^2\sin^2{x} + \cos^2{x})dx $$ For $a > 0$.  This is what I did: $$ I(a) = \int_{0}^{\pi/2} \ln(a^2\sin^2{x} + \cos^2{x})dx \\\ I'(a) = \int_{0}^{\pi/2} \frac{2a\sin^2{x}}{(a^2\sin^2{x} + \cos^2{x})} dx \\\   I'(a) = \int_{0}^{\pi/2} \frac{2a}{(a^2 + \frac{\cos^2{x}}{\sin^2{x}})} dx  \\\ I'(a) = 2a \int_{0}^{\pi/2} \frac{1}{a^2 + \cot^2{x}}dx  \\\ I'(a) = \frac{2}{a} \int_{0}^{\pi/2} \frac{1}{1 + \frac{\cot^2{x}}{a^2}}dx $$ Here I tried to substitude $\frac{\cot^2{x}}{a^2} = t$. This should lead me to $\arctan(something)$ (I write $\arctan{x} = \tan^{-1}{x}$.) But I got stuck.     After I get the derivative I should integrate it back to get $I(a)$. Also there are steps that need some prepositions to be checked. Could one help me with this integral and also to clarify the steps that need special attention; such as the second step, where I can get the derivative $I'(a)$ only if the function under the integral can be differentiated? It must be possible to find its derivative.


When we handle flags through 10K tools we get 50 random posts in the flags tab via  and at the bottom we have a link which loads 50 more random posts which redirects to the same page (in other words it just refreshes the page). That is fine.  Now if we select a specific type of flags. E.g. 67 X not an answer. it will redirect us to  which also loads 50 random posts and at the bottom of page it says:     Showing 50 random posts; get    But you can see that 50 more link redirects us to https://stackoverflow.com/tools/flagged which should be https://stackoverflow.com/tools/flagged?flagtype=answernotananswer IMO. Because I am on specific flag type page.  PS: I just earned that privilege few days ago. So not sure whether it's a bug or by design. In Meta we rarely get few flags so I don't have experience here.

When working my may through items in , I find it more efficient to handle one flag type at a time.   If there are many items for a flag type, only 50 random posts are shown at a time which is great. However, when I reach the bottom of the list and click "50 more", the selected flag type is forgotten and I end up with 50 random questions of all types.  Feature Request: Can the "50 more" link take into account the selected flag type?    Sure, I can achieve that quickly using CtrlHome + CtrlR (or CtrlL + ENTER), or create a userscript to apply the current querystring to the "50 more" link. However, an official solution would be nice.


I read in  (section 11.2) that the charge of the proton is, apart from the sign, approximately equal to that of the electron.. What bothers me is the word approximately, shouldn't $q_e=q_p$ because any small difference on the atomic scale will induce a huge electric charge for macroscopic bodies.

What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of photon field, but is this explanation enough? Do we have some experimental evidence that quarks have 2/3 and -1/3 charges? By the way I think about bare charge of electron and proton. And I am also wondering if this can be explained by Standard Model.


I googled about this "be it" thing and I found a little sth about it, I learned it's an old subjunctive inversion, but I can’t understand meaning of the sentence below:  But such an “objective” account is not adequate to resolve the conflict—be it to resolve the conflict by defeating one side.

What does be it mean in this context and what kind of sentence is this? (grammatically)     There is no one in our society who is not ethnocentric to some degree, no matter how liberal and open-minded he or she might claim to be. People will always find some aspect of another culture distasteful, be it practices, a way of treating or relatives, or simply a food that they cannot manage to get down with a smile.


I am new to C# coding. I implemented following code and facing a warning.  class Base {     public static Base Getinstance() {         return new Base();     } }  class Derived : Base {    // getting warning Derived.getInstance()' hides inherited member    //'Base.getInstance()'. Use the new keyword if hiding was intended    public static Derived Getinstance() {         return new Derived();    } }   In order to remove the warning I have 2 options   use virtual in base class write new in derived class any other (please suggests if have anything else)   Which will be the right way to solve this warning?

What are differences between declaring a method in a base type "virtual" and then overriding it in a child type using the "override" keyword as opposed to simply using the "new" keyword when declaring the matching method in the child type?


In visual studio if exception is unhanded and studio cannot find source code that caused it, screen like this will be shown:  And that's ok. Let's say I don't need the code, but how can I at least see some exception info except type and message? Inner exception would be helpful for example. Edit: As suggested in @victor-alexandru-papa's answer if "Break when thrown" for Common Language Runtime Exceptions is checked, it will indeed show more info about exception. (in my case break mode was caused by exception in not awaited task). Wanted to do this edit to add some screenshots of what happens. So, as you can see, new View details button appears, which actually shows details of the exception. Also I can see stack now and state of my application when exception was thrown.

I would like Visual Studio to break when a handled exception happens (i.e. I don't just want to see a "First chance" message, I want to debug the actual exception).  e.g. I want the debugger to break at the exception:  try {    System.IO.File.Delete(someFilename); } catch (Exception) {    //we really don't care at runtime if the file couldn't be deleted }   I came across  notes for Visual Studio.NET:     1) In VS.NET go to the Debug Menu >>   "Exceptions..." >> "Common Language   Runtime Exceptions" >> "System" and   select "System.NullReferenceException"      2) In the bottom of that dialog there   is a "When the exception is thrown:"   group box, select "Break into the   debugger"       3) Run your scenario. When the   exception is thrown, the debugger will   stop and notify you with a dialog that   says something like:              "An exception of type "System.NullReferenceException" has   been thrown.              [Break] [Continue]"       Hit [Break]. This will put you on the   line of code that's causing the   problem.   But they do not apply to Visual Studio 2005 (there is no Exceptions option on the Debug menu).  Does anyone know where the find this options dialog in Visual Studio that the "When the exception is thrown" group box, with the option to "Break into the debugger"?  Update: The problem was that my Debug menu didn't have an Exceptions item. I customized the menu to manually add it.


Shog explained :     SO questions are penalized... if your goal is to get more SO questions into the list, you have a bit of a hump to climb.   How is this achieved?  Or, to be more precise, is it technically possible to set up similar "penalty" for some other site? If , what is needed in order to  ask for similar protection penalty to be established for a particular site?

To start with, I am aware that hot questions from larger sites are somehow "penalized" and :     This is designed to ensure that a single site doesn't dominate the list, and that users see a good sampling of questions that are likely to interest them throughout the network...   I would like to understand how is hotness score really calculated at these sites. The reason why I ask is that per my observations, this seems to be quite different than is documented in the . Specifically, I would like to understand the difference in the impact of answer(s) score and aging factor.  Regarding impact of answers score, my observations of hot questions from smaller sites appear to be in agreement with known formula: (MIN(AnswerCount, 10) * QScore) / 5 + AnswerScore. For example, a question with low score (+1, +2) can get into hot list if it has got answer(s) with sufficiently high score.  At larger sites, this doesn't seem to be the case. Say, it looks like Stack Overflow questions just don't enter hot list until they reach certain score (+6,+7), no matter how many answers are there and how high is their score.  Does system simply totally ignore answers until question reaches certain score?  Another thing I noticed is that questions seem to age away from the hot list 2-3 times faster than ones from smaller sites (having comparable question and answers scores). Granted, this is harder to track and I am not yet sure if I figured that correctly. Do larger sites questions age away faster than those from smaller sites?    For those interested, here is a (partial) list of example questions I studied before asking this: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , .  Although above examples are only from Stack Overflow, my question isn't (I only used it as an example of a large site in my studies). I would like to understand if hot questions from other larger sites are handled in a similar way.


How can I show this? I was doing some proves, and this question came out of nowhere, but I felt curious about this and so I tried this. The question is that given any $k \in {{\Bbb Z}^ + }$ such that $k \geqslant 5$, show that ${6^k} + 1$ is composite. This question looks and feels extremely difficult to prove for me, and so I want help from this. Luckily, I did some proves such as using By Induction, By Contradiction, and more, and nothing worked. Also, I tried looking this problem through the Internet, and nothing... What I tried to do was the following, though: Show that if $$A = \{ {6^k} + 1|{6^k} + 1{\text{ is prime}}\} $$then $A = \{ 7,37,1297\} $. Especially, only when $k = 1$, $k = 2$ or $k = 4$, ${6^k} + 1$ is prime. Or equavilently, ${6^k} + 1$ is prime iff $k = 1$, $k = 2$ or $k = 4$. Any ideas? Thanks, Joshua. Update: This question is already answered. Thanks, everyone for helping. Update 2: I think that I can prove this (but not completely). Proof: Let $k \in {{\Bbb Z}^ + }$ and odd. Then $k = 2m + 1,m \geqslant 2$. $\Rightarrow {6^k} + 1 = {6^{2m + 1}} + 1 = 6 \cdot {36^m} + 1$. Since $36 \equiv 1(\bmod 7) \Rightarrow 6 \cdot {36^m} + 1 \equiv 6 \cdot {1^m} + 1 = 6 \cdot 1 + 1 = 7 \equiv 0(\bmod 7)$. Hence when k is odd, $6^k + 1$ is composite. If $k = ab$ and $b$ is odd, then $6^k + 1 = 6^{ab} + 1 = 6^{ab} + 1 \Rightarrow 6^a + 1|(6^{ab}+1)$.

Does anyone know whether there are only finitely many of primes of the form $6^{2n}+1$, where $n$ zero or any natural number?


I have an HP Z230 workstation which came with Windows 8.1 Pro downgraded to Windows 7 Pro preinstalled.  I have since replaced the harddrive and installed Ubuntu 16.04 on it.  I have also installed VirtualBox, and installed Windows 10 Pro in a VM.  From looking online I understand the product key is in the UEFI firmware?  The activation screen in Windows 10 says:     We can't activate Windows on this device because the previous version of Windows was not activated prior to upgrading to Windows 10. Go to the Store to buy genuine Windows. Error code: 0x803F7001   Questions:   Am I able to use the Windows 8.1 product key from my bios to activate Windows 10 in my vm? If so, how can I retrieve the product key (using Ubuntu 16.04)?

I have seen other SuperUser questions on this topic:  |   However, all of the answers assume you have Windows 8 running.  I've already done a clean install of Ubuntu 13.04 on my new laptop, and I'm trying to set up a VM environment for those occasional programs that just absolutely refuse to run even with Wine.  I saw this image on another answer:     So it appears that the key should somehow be available via ACPI. However,  I've tried ls /proc/acpi and that turns up nothing useful as far as I can see, and acpitool isn't helping me at all.  How the heck can I get the product key out?  EDIT: I have tried running RW-Everything via Wine (the  program), but it is unable to 'install its driver'. So no dice there.


I recently purchased a new Dell laptop. It weighs 1.34 KG. I want to add movies in my laptop. Will my laptop weight increase if I add movies?

What is the physical weight of one gigabyte of memory/storage? Lets say this is on a hard disk.  What is the weight associated with the atoms that are actually storing the data on the disk?  How has this value changed as densities of disks have increased?


I was doing some messing around on excel to answer this brain teaser:  In autumn the amount of leaves falling from a tree get doubled after every hour. The tree is leafless after 9 days. How many hours does it take until half of all leaves have fallen down?  WARNING: Brain teaser answer below, if you want to work it out yourself.  On Excel I was simulating doubling the number of leaves falling every hour, finding the cumulative leaves that have fallen, and then the proportion of the total leaves that have fallen (note 9 days = 216 hrs):  hour    leaves falling   cumlative      proportion of leaves         that hour                       that have fallen 1       1                1              9.49557E-66 2       2                3              2.84867E-65 3       4                7              6.6469E-65 4       8                15             1.42434E-64 5       16               31             2.94363E-64 .       .                .              . 211     1.6455E+63       3.29101E+63    0.03125 212     3.29101E+63      6.58202E+63    0.0625 213     6.58202E+63      1.3164E+64     0.125 214     1.3164E+64       2.63281E+64    0.25 215     2.63281E+64      5.26561E+64    0.5 216     5.26561E+64      1.05312E+65    1   It takes 215 hours for the first half to fall, and then the second half all fall in the final hour.  I can see this, but don't fully understand why this is.   What I can see is the second column is just the series $2^n$, where $n$ is the $hour-1$, and that the third column is one less than the next $2^n$, i.e.: $$ 2^{n+1} = 1 + \sum_{i=0}^{n}2^i $$  No doubt that, at hour 215, this 1 before the sum is so insignificant that: $$ 2^{n+1} \approx \sum_{i=0}^{n}2^i $$ for large $n$.  I can see therefore that, for all intents and purposes, half of the leaves do fall in the last hour.  My question is, why does: $$ 2^{n+1} = 1 + \sum_{i=0}^{n}2^i $$ Is there any intuitive logic that can explain this? Or, if not, a mathematical proof?

I know that the sum of power of $2$ is $2^{n+1}-1$, and I know the mathematical induction proof. But does anyone know how $2^{n+1}-1$ comes up in the first place.  For example, sum of n numbers is $\frac{n(n+1)}{2}$. The idea is that we replicate the set and put it in a rectangle, hence we can do the trick. What is the logic behind the sum of power of $2$ formula?


I have QGIS 2.10.1 Pisa and GDAL 1.11.2, and I can't open MrSID (.sid) images en QGIS, I have lost three days trying to make it work, but I can't make it.   My Linux is 14.04 trusty tahr.

I need some help importing MrSID Raster files in QGIS. I am running 2.6.0 on Linux Mint 17. After an internet search I have found a couple of resources that are perhaps outdated. The most promising is found here :    However when I attempted to follow the instructions my terminal and I could not find the file "libgdal-mrsid-src" on either the stable or unstable Ubuntu GIS repos. Has anyone had success or could lead me in the right direction?


I have multiple remote references, and there's no "git remote prune --all" so I attempted "git remote show | xargs -n 1 git remote prune" but it doesn't work. I'm running msysgit 1.7.4. I know it works in Linux (well "git remote show | xargs git remote prune" does) but I just get no output in msysgit, and I know it's not working as I can still prune after running that.  "git remote show | xargs -n 1 echo git remote prune" shows me it's compiling the "git remote prune public1" commands correctly.  Any ideas?

How can I make xargs execute the command exactly once for each line of input given? It's default behavior is to chunk the lines and execute the command once, passing multiple lines to each instance.      From :       find /path -type f -print0 | xargs -0 rm      In this example, find feeds the input of xargs with a long list of file names. xargs then splits this list into sublists and calls rm once for every sublist. This is more efficient than this functionally equivalent version:      find /path -type f -exec rm '{}' \;   I know that find has the "exec" flag.  I am just quoting an illustrative example from another resource.


While reading the O'Reilley book on Apache Web Server, they gave an example on using ifconfig to set ip aliases on an interface:  ifconfig ep0 192.168.123.2 ifconfig ep0 192.168.123.3 alias netmask 0xFFFFFFFF ifconfig ep0 192.168.124.1 alias   I became curious: how would you do the same thing using the iproute utils on Linux?

I am wondering what is the difference between:  # ifconfig eth0:0 1.1.1.1/24   and just  # ip addr add 1.1.1.1/24 dev eth0   Btw I cannot do  # ip addr add 1.1.1.1/24 dev eth0:0 RTNETLINK answers: File exists   In ip addr show it appears differently :  eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000  link/ether 8c:ae:4c:fe:1f:75 brd ff:ff:ff:ff:ff:ff inet 1.1.1.1/24 brd 1.1.1.255 scope global eth0:0 ---> with ifconfig inet 2.2.2.2/24 scope global eth0 ----> with ip   When should I prefer the first way and when should I prefer the second way? It seems more cool to


I saw it in Windows 10. Notebook is connected to WiFi network via WPA2 Enterprise, let's call it "work network". I can't connect to this network from my smartphone but I can make WiFi hotspot in Windows and connect to it with smartphone. Windows is automatically share "work network" to hotspot WiFi and I can use this network to connecting to internet. Is it possible to achieve on Ubuntu?

I am connecting to a WiFi network through my laptop in Ubuntu. Now I need to share my Internet connection with my wife's netbook because her netbook is not able to connect to that WiFi network directly, because of its weak signal.  How can I do that in Ubuntu?


I saved a web page as a pdf.  I would like to add watermark to this existing pdf.  I googled and got some answers either using something like Adobe Acrobat DC or using a programming language like Python.  Is it feasible to add watermark to this existing pdf within tex, latex?

I saved a web page as a pdf.  I would like to add watermark to this existing pdf.  I googled and got an approach that suggest to merge 2 pdf, the original one and the one contains watermark.  this code could used to generate a watermark pdf  \documentclass{beamer} \usepackage[printwatermark]{xwatermark} \usepackage{xcolor} \usepackage{graphicx} \usepackage{tikz} \usepackage{lipsum}  \newsavebox\mybox \newwatermark*[   allpages,   angle=45,   scale=6,   xpos=-20,   ypos=15 ]{\usebox\mybox}  \begin{document}  \savebox\mybox{\tikz[color=red,opacity=0.3]\node{DRAFT};}  ab  \end{document}   although there have to be some additional characters ("ab" in this case).  is it possible use latex to generate a pdf that only contains watermark without any other additional characters?


I need to convert black paths in image below to constant width lines. What strategy I should follow?

I need to trace picture below to vector.  After tracing it with black and white mode I got result below that I don't like. I would like to have all lines to be in the same constant width.  What tracing strategy I should use to get needed result?


I have a custom Object (Candidate ) with the following status picklist values  Picklist1 picklist2 Piclklist3  I would like to create the horizontal Time line using visual force page  that would depend on the status of the picklist. This can be achieved by using the formula but i would like to have the banner using VF on the detail page of the record. (EX: By default the status of the candidate would be "picklist1" and when the status is changed to "Picklist2" the image should move to that status on the time line.)[![enter image description here][2]][2]

I want to create STAGE based chart in my salesforce org. Please find the screenshot for the sample.


I want to be able to check the current content of an iframe tag.   Example  <iframe src="bing.com"> </iframe>   I want to be able to check what the user has clicked inside the iframe (in this content probably their search query) and see the current URL they are accessing inside the iframe.   Is this even possible? And if so, how can I accomplish it. Thanks in advance

I would like to manipulate the HTML inside an iframe using jQuery.  I thought I'd be able to do this by setting the context of the jQuery function to be the document of the iframe, something like:  $(function(){ //document ready     $('some selector', frames['nameOfMyIframe'].document).doStuff() });   However this doesn't seem to work. A bit of inspection shows me that the variables in frames['nameOfMyIframe'] are undefined unless I wait a while for the iframe to load. However, when the iframe loads the variables are not accessible (I get permission denied-type errors).  Does anyone know of a work-around to this?


I'm working with a series of forest polygons (geodatabase feature classes), which I'm trying to clip to an area with a specific land use history (marked as "undisturbed" in the screenshot below)in ArcGIS 10.3.1. I'm then hoping to filter out all polygons less than 1 hectare for additional analysis.   My problem is that some of of the forest polygons ("cove_ecogroup" below) overlap the larger land use polygon in multiple areas, which leaves me with some disconnected features in my output. This is fine, except that it makes my 1-hectare filter impossible because these shapes are being stored as larger than they actually are because they retain the FID of the original feature instead of splitting into multiple new features (See image 2).  Is there a way to split these into multiple features so that I can filter out everything under 1 hectare? This analysis covers hundreds of thousands of acres, and so I won't be able to edit each new polygon individually.

I created voronoi polygons after which I dissolved them on the basis of one attribute. Now there are cases where in for one single attribute "abc" I have3 polygons at different places with same object id. I would like to break these into 3 polygons as they are at different locations.  Is there any tool in ArcGIS Desktop or QGIS which can help me in doing that?


After I've found  post I'm curious what kind of algorithms they use to generate these shapes (second image).   I can't imagine that the basic shapes are basing on a perlin or simplex noise or a voronoi diagram. With voronoi I'm a bit uncertain to be honest.  Well, so what do you think. What algorithm could be used to generate biome borders like they do?

I'm looking for ways to generate random biome borders (like what Minecraft has).  One technique involves choosing specific biomes based on (eg) a rainfall map and a temperature map. But that just determines which biome to place, not where the borders between biomes are.  I don't want to use quantized Perlin noise directly; that would generate certain quantized values strictly within other zones, whereas I'd like finer control over which biomes can abut others. For example, in Minecraft one can see mountainous terrain, forests, plains, or deserts right next to the ocean.  Many of the solutions to "the biome problem" propose computing the whole universe in a heuristic manner. I want to generate infinite terrain, and to me that suggests the algorithm be strictly functional: given an X,Y value (and a world seed) the algorithm can easily spit out a biome value.  So, my question: what are some techniques for identifying random, non-trivial-sized, contiguous chunks of terrain to be of a given biome?


what are some applications of group theory? Group theory seems to be rather abstract.

I would like to know whether there are examples where finite group theory can be directly applied to solve real world problems outside of mathematics.  (Sufficiently applied mathematics such as cryptography, coding theory, or statistics still count.)  Let me clarify: I am not interested in applications of elementary group theory which happen to involve finite groups (e.g. cyclic/dihedral/easy groups as molecular symmetries).  I am interested in applications of topics specifically coming from finite group theory as a discipline, like one might see in , , or .  "The Schur multiplier has order 2640, so we should point the laser that way."   "Is this computer system secure?"  "No - Frobenius kernels are nilpotent."  I'm aware of , but many of the applications listed there are inside mathematics or fall in the "applications of easy groups" category.  It is entirely possible that what I'm looking for doesn't exist, and that finite group theory is still an untouchable, pure subject, like number theory in the days of G. H. Hardy.  But perhaps not.  Does anyone know of any applications of the higher level stuff?


Let's say I have a website with a domain name, of course. The domain name has:     One A record(example.com) which points to the origin server(or load balancer).  One CNAME record(cdn.example.com) which points to a CDN server.    Now, my question is, when a client makes a request to cdn.example.com then how is this request directed to the nearby CDN edge server? Who resolves this? Is it the DNS server maintained by the ISPs, the CDN itself, or something else?

I found  how a CDN works. But there is one thing I don't really understand. Let's assume I setup multiple DNS servers at my location and they use the nameserver domains dns1.example.com, dns2.example.com and dns3.example.com. This DNS servers are able to deliver a server IP depending on the visitors location (ping, geo database, browser language or whatever). Now I update this nameserver settings for my domain www.example.org at the registry.  Now, the very first request on www.example.org with an expired TTL tries to resolve the domain. It asks:   the local .hosts/DNS, if TTL expired: the internet providers DNS, if TTL expired: the root DNS, if TTL expired: my local dns1.example.com   But if I understand it correct, the new IP is then added to all these nameserver caches until the TTL expires again. So how is it possible to send other IPs to the visitor depending on his location?  In  theandym said the request is "forwarded", but I don't think this is how a CDN works, because "forwarding" means lengthen the transmission way resulting a longer loading time. Or does a CDN require zero TTL for the domain?  Update1 Through  I found  describing how they optimized CDN performance. It did not explain how the CDN works in general, but there were interesting explanations like the following:     Thereafter, whenever a client attempts to fetch content hosted on the   CDN, the client is redirected to the node determined to have the least   latency to its prefix. This redirection however is based on the prefix   corresponding to the IP address of the DNS nameserver that resolves   the URL of the content on the client’s behalf, which is typically   co-located with the client.   This means Google checks at first the latency of all IP prefixes and defines a DNS resolution table (?) for all available prefixes. And if a visitor has the IP 198.51.100.231 the Google server IP is used, that is set for the prefix 198.51.100.0. But again: How does Google's DNS know which IP the visitor is using? Most visitors resolve Google's domain through their internet provider and by that the resolving is done through those external DNS servers or not?  As an additional example: If I start a DNS resolution for the domain facebook.com with different online tools (hosted in different countries) it is resolved to different IPs with different domains like:   31.13.92.36 Reverse: edge-star-mini-shv-01-frt3.facebook.com 31.13.76.68 Reverse: edge-star-mini-shv-01-sea1.facebook.com 31.13.69.228 Reverse: edge-star-mini-shv-01-iad3.facebook.com 157.240.2.35 Reverse: edge-star-mini-shv-01-ort2.facebook.com   After that I thought it could depend on the DNS server location used by the visitor, but I tried my own (Deutsche Telekom, Germany), Google's (8.8.8.8) and a major one from France (Orange) and they all returned for facebook.com the IP 31.13.92.36.


I have done all of the possible updates rfkills and created "wireless-info.txt" added all the possible drivers from HP and still no wifi found.  I have new HP with Realtek Semiconductor Co., Ltd. RTL8723DE 802.11b/g/n PCIe Adapter

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


$\beta +$ decay is where a proton gets turned into a neutron and a positron and a neutrino.  However, a neutron is heavier than a proton, so obviously this reaction is endothermic. So then, why does it happen? I've seen an explanation here in the question    It describes that the final binding energy of the nucleus increases, thus making it possible by becoming more stable. But what actually causes the reaction to go in the first place? It's like saying this ball will go down the hill because it will lose energy - what gives it the nudge required? Is it something like energy from external gamma rays or something?

The mass of a neutron is greater than mass of a proton so how is it possible in positron emission for a proton to form a neutron and a positron?


I'm new to R and don't know how to deal with this warning I get while doing negative binomial log regression: Warning in anova.negbin(nb.MouthOpen) : tests made without re-estimating 'theta' Can I ignore this or does it have an effect on the results I get? I have no idea of what kind of information you need to help me...does the code help? The data are behavioural observations made by a 1-0 sample method and is then compared against a noseband tightness score. It's for my master thesis. summary(nb.MouthOpen <- glm.nb(cbind(NosebandMouthOpen,NosebandTotalscans-NosebandMouthOpen) Noseband TightnessNoseband, data = Noseband)) anova(nb.MouthOpen) (est <- cbind(Estimate = coef(nb.MouthOpen), confint(nb.MouthOpen))) exp(est) deviance(nb.MouthOpen)

I'm new to R and don't know how to deal with this warning I get while doing negative binomial log regression:  Warning in anova.negbin(nb.MouthOpen) : tests made without re-estimating 'theta'  Can I ignore this or does it have an effect on the results I get? The data are behavioral observations made by a 1-0 sample method and is then compared against a noseband tightness score. summary(nb.MouthOpen <- with(Noseband, glm.nb(cbind(MouthOpen, Totalscans-MouthOpen) ~                                                  TightnessNoseband)) anova(nb.MouthOpen) (est <- cbind(Estimate = coef(nb.MouthOpen), confint(nb.MouthOpen))) exp(est) deviance(nb.MouthOpen)


This is pretty much a repeat of the question from social.technet.microsoft.com:   After a quick Google search, the above link is the only link I could find which was directly related to what I am looking for. But on that page the discussion seems to have decayed into some inconclusive babble, and I thought Superuser might be a good place to get a conclusive result (even if it is in the negative).  So is there a way I can tell Windows to shutdown the machine after it is done installing the updates? Please note that I want it to shutdown and not restart, so that my PC doesn't stay on the whole night. I thought of scheduled tasks, but am not able to come up with a good argument that I can pass to make it do what I need it to.

I know that there is a simple way to shutdown the computer in command prompt, but is it possible to do system updates and then shutdown the computer in command prompt?   For example, when Vista needs to install updates, it will let me install them and shut down by clicking the Shut Down button (while relegating the normal shut down button into the menu). So is there a command to do this in command prompt?


How to redirect all subdomains to the root domain?  It works for non-SSL domains, but doesn't work for SSL domains!?  eg  Works!     wee.domain.com => https://domain.com www.domain.com => https://domain.com  Doesn't work! (no redirecting) https://wee.domain.com => https://domain.com https://www.domain.com => https://domain.com   vhosts  <VirtualHost *:80>     ServerName domain.com      #   force https     RewriteEngine On     RewriteCond %{HTTPS}        off     RewriteRule ^           https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301,QSA]      ...  </VirtualHost>  <VirtualHost *:443>     ServerName domain.com      SSLEngine on     ...  </VirtualHost>  <VirtualHost *:80>     ServerAlias *.domain.com      RewriteEngine on     #   Redirect all subdomains to root     RewriteRule ^           https://domain.com [L,R=301]      ...  </VirtualHost>  ##########   This vhost is not working   ###############  <VirtualHost *:443>     ServerAlias *.domain.com      RewriteEngine on     #   Redirect all subdomains to root     RewriteRule ^           https://domain.com [L,R=301]      SSLEngine on     ...  </VirtualHost>

This is a  about Apache's mod_rewrite.   Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:   Changing HTTP to HTTPS (or the other way around) Changing a request to a page which no longer exist to a new replacement. Modifying a URL format (such as ?id=3433 to /id/3433 ) Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun. Anything you want to mess around with URL   Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!  How can I become an expert at writing mod_rewrite rules?   What is the fundamental format and structure of mod_rewrite rules? What form/flavor of regular expressions do I need to have a solid grasp of? What are the most common mistakes/pitfalls when writing rewrite rules? What is a good method for testing and verifying mod_rewrite rules? Are there SEO or performance implications of mod_rewrite rules I should be aware of? Are there common situations where mod_rewrite might seem like the right tool for the job but isn't? What are some common examples?   A place to test your rules  The  web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.


I was using a grammar correction software to review an article. The software suggests to insert a comma in the following text:  In each part, the warping function creates feature maps of the input data and the wavelet filters extract higher frequency information from the input and propagate it forward.  The comma is suggested between and and data in data and the wavelet. I was not sure why it is suggested, if it is a correct one, and what type of comma it is.

I read this sentence on an educational website:     Now times have changed and you are ready for situations involving forces in two dimensions.   Shouldn't there be a comma before and, since the subject of the sentence has changed (things vs. you)?      Now times have changed, and you are ready for situations involving forces in two dimensions.   What is the exact comma rule for joining two clauses with and?


He believed, moreover, that children are innately good.   I've seen this sentence in an English test book. Shouldn't we use "were" instead of "are" in this sentence?     He believed, moreover, that children were innately good.   If "are" is correct here, that means we can also say:  He believed that I am a good person.  I would use "was" instead of "am" here. But the first sentence confuses me. If a sentence starts with past tense, shouldn't it continue with past?

Suppose Pat is male. Which one is correct?     I found out Pat is male.      I found out Pat was male.   Does the following change make any difference?     She said Pat is male.      She said Pat was male.   Suppose you created a mathematical model. When you are describing a result, which one (or neither) is correct?     The model analysis shows that the equilibrium is stable.      The model analysis showed that the equilibrium is stable.


Let $f: E\rightarrow S$ be a family of elliptic curves, i.e. a proper flat morphism of schemes whose geometric fibers are genus $1$ curves, along with a section $e:S\rightarrow E$. Then there is an invertible $\mathcal O_S$-module $\omega = f_*\Omega^1_{E/S}$ on $S$, sometimes called $\mathrm{coLie}(E)$ because at $s\in S$ the fiber of $\omega^{-1}$ at $s$ is the Lie algebra of the elliptic curve $E_s$. I've seen it claimed that $\omega\cong e^*\Omega^1_{E/S}$, though it's not clear to me why this is true, or how even to define a map $f_*\Omega^1_{E/S}\rightarrow e^*\Omega^1_{E/S}$. I'd appreciate an explanation of why this isomorphism holds (or a reference giving such an explanation). Thanks!

Let S be a scheme, $p:E\rightarrow S$ be an elliptic curve with zero section $e:S\rightarrow E$. My question is: Are $p_*(\Omega_{E/S}^1)$ and $e^*(\Omega_{E/S}^1)$ isomorphic? I think it's right because I saw both definitions in different notes and they seem to represent the same thing. Thank you!


I have a table with products like  Products  id name styles_id   I also have a table with styles like  Styles  id name   When I add a style to a product I use a foreign key id value from the Styles table. I do this for a few years now on a lot of projects but I was thinking WHY? It would be a lot easier to get the products if I have a Styles table with a name as primary key and without an id. So I do not have to do a join to get the style name of the product. I see it is done a lot but what are the advantages of the id in the Styles table?

Here we go again, the old argument still arises...   Would we better have a business key as a primary key, or would we rather have a surrogate id (i.e. an SQL Server identity) with a unique constraint on the business key field?   Please, provide examples or proof to support your theory.


While working with the ModelBuilder, I added 2 columns to the data. After you have done "Summary Statistics" according to the GridID, you know the output product in tabular form. I wanted to print the table with the join based on the common column GridID's. But there is a problem here. During the Add Join process, the model wants the input product to be in Table Of Contents.  So it want to data as a "parameter". When I run the model from the inside, I say "Add to Display" to the latest product. Thus, the model sees it and accepts it as input. But when I run the model from the outside, it gives error because there is no input / output product in "Table of Contents". How can i solve it?

I'm trying to create a tool in ModelBuilder that will take a new point from a user, create a feature class for this point and display it on a map.  What I've done is:   I've created a feature class for a point-like feature in ArcCatalog. I've prepared a really simple model in ModelBuilder, that starts with a feature set variable (which takes the feature class as a schema and symbology file). The variable is marked as a parameter. Next I'm using the Copy Features tool that takes the variable as input and saves it as a feature class in my scratch workspace. The output feature class is marked as a parameter with the 'add to display' option.   After the module is run I get a shapefile in my scratch workspace. I can add it manually to TOC and it contains the selected point. However no matter what I do, I can't display it in TOC automatically after the model completes.  There is a known issue described in several places that doesn't allow to display newly created layers in TOC when model finishes with the 'add to display' option. However there's a quick workaround, which is to mark the output layer as parameter. In my case it doesn't work.  I'm using ArcGIS for Desktop 10.1 on Windows 7 x86_64.


Let $p$ prime be a number and let $a$ be a natural number so that $a<p$. prove that $a|p+1$ if and only if there are $M,N$ that are naturals so that $a/p = 1/N + 1/M$. I have tried a lot of algebraic games to get to something like $p+1 = a\pmod{\text{something}}$ to show that $a|p+1$ but I had no success. I really don't know where to begin.

$a\in \mathbb{N}$, $p$ prime, $a<p$ prove that $a\mid p+1\iff \exists\, b,c\in\Bbb N:\dfrac{a}{p}=\dfrac{1}{b}+\dfrac{1}{c}$ my attempt: $a\cdot b \cdot c=p\cdot(b+c)$ . i dont know how to use the given $a\mid p+1$


I want to include an article (with documentclass: IEEEtran)  into a report (with another, company specific, documentclass). I want to refer in the article (myarticle.pdf) to the ten appendices of the report.  I tried it with  include pdf:  \documentclass{Report}   \usepackage{pdfpages}   \begin{document}    Report   includepdf{myarticle.pdf}%refer in this article to ~\ref{app:req}   \appendix   \chapter{Requirements}% The first appendix   \label{app:req}   \end{document}     The problem is that with pdfpages the article can not refer to the appendices of the report. How can I solve this?

Sometimes I want to refer (using \ref) a \label from some other tex file. What is the right way to do it?  (It's, of course, possible to \include all files in one and then use \includeonly — but it breaks e.g. page and section numbering.)