I have a fixed header and a fixed footer that should always be visible in the window.  The problem: I would like to have a "main box" expand between the header and the footer. In that main box is the text box the height of that box should be relative to the distance to the header and footer. I think this picture explains better what I'm trying to archive:    The header and footer could also have a fixed height.

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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; */ }

...

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     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.


Thirteen cards numbered $1$ to $13$ are shuffled and dealt one at a time.  "Match" occurs on deal $k$ if $k$th card revealed is card number $k$   Let N be the total number of matches that occur in the thirteen cards. Determine $E[N]$  Hi, the above is the problem that I have a trouble with.   My first approach is that probability of first card with number $1$ is $\frac{1}{13}$  and probability of second card with number  $2$ is $\frac{1}{12}$.  It keeps going until last card, so I think $E[N]$ is $\frac{1}{13}+\frac{1}{12}+\frac{1}{11}\cdots+1$   I don't think this is right.   There is a hint saying that "Write $N= 1{A1}+1{A2}+....+1{A13}$, where $A_k$ is the event that a match occurs on deal $k$"  Can anyone help me out?

There are $40$ letters and $40$ envelopes with addresses. The letters are put in envelopes at random. What is the expected number of letters in their corresponding (correct) envelopes ?  One envelope can hold only one letter.  I start with $E(X_i)=1\cdot\dfrac{1}{40}+0\cdot\dfrac{39}{40}=\dfrac{1}{40}$.  $X_i$ being the $i^{th}$ letter placed correctly or not ($1$, if correctly placed and $0$, if not). I need to calculate the expected count of letters assigned correctly.  Then add up all $\implies$ $E(X_1+X_2+\ldots+X_{40})=\underbrace{\dfrac{1}{40}+\dfrac{1}{40}+\ldots+\dfrac{1}{40}}_{40\text{ times}}=1$  Now my doubt is that if I put $39$ letters correctly, the $40^{th}$ one will be automatically assigned correctly . So should I add only $39$ times ?   Any other mistakes I may be doing here ? Please advise.


I'd like to run a Linux process in a fake-write environment where all file writes (with the write(2) system call) are redirected to an in-memory cache, and subsequent reads (of the same region only) will be served from the cache. The cache can be discarded after the process finishes.  The files the process will be modifying are huge (several terabytes), but the total amount of written data is small (a few megabytes). So overlayfs is not an option, because I don't have several terabytes of free space.  Please note that I don't care about fake device nodes or fake permissions, thus fakeroot(1) doesn't help me.  This should be possible to implement with LD_PRELOAD, ptrace(2), fuse(8) or . Is there an existing tool which will do it for me, like this:  $ fakewrites ./myprog myfile.dat

GNU/Linux has union mount that overlays dirs. So you can mount a writeable dir on top of a read-only dir. When the writeable dir is unmounted the read-only dir is untouched.  I am looking for the same functionality for block devices - preferably with the writeable part stored in a file. So I would like to run something like:  device-setup /dev/newdevice /dev/read-only-device overlayfile   If I write to /dev/newdevice the changes should be stored in overlayfile. If I read the sectors written to, I should get the data from overlayfile. If I read sectors not written to, I should get the data from /dev/read-only-device.  Does such a tool exist?


My book "Fundamentals of Physics" by Halliday, Resnick, Walker says:  The net external torque acting on a system of particles is equal to the time rate of change of the system's total angular momentum  Then it says:  Caution: Torques and the system's angular momentum must be measured relative to the same origin. If the center of mass of system is not accelerating relative to an inertial frame, that origin can be any point. However if it is accelerating then it (center of mass) must be the origin. For example, consider a wheel as the system of particles. If it is rotating about an axis that is fixed relative to the ground, then the origin for applying the formula (net external torque acting on a system =time rate of change of the system's total angular momentum) can be any point that is stationary relative to the ground. However, if it is rotating about an axis that is accelerating (such as when the wheel rolls down a ramp), then the origin can be only its center of mass  My question: Suppose a uniform circular disk is rotating about an axis Q that is x meters away from center of mass. It is also accelerating (linear as well as rotational) just like that wheel rolling down the ramp given in example. Can't we apply this formula about axis Q? According to the text given in book "when the system is accelerating then center of mass must be the origin". Here in my question The center of mass is rotating, so how can we use it as origin?

I am studying angular momentum and I get the concept that it has a meaning or it is defined only with respect to a  certain point (often called as origin). I was looking at the realtionship between torque and angular momentum around an origin i.e.  net torque  = Rate of change of angular momentum (equation 11.29 in the picture). I think i get this relationship. Where I got confused when author adds a caution (full quote below) to the equation saying that:  If the center of mass of the system is not accelerating relative to an inertial frame, that origin can be any point.  However, if it is accelerating, then it must be the origin.  I am not sure if I get that statement and caution.  Not sure what the author means by the “origin” here.  Can't the origin be any point that we choose?   Let $\vec{\tau}_{\mathrm{net}}$ represent the net external torque, the vector sum of all external torques on all particles in the system.  Then we can write Eq. 11-28 as \begin{equation}   \vec{\tau}_{\mathrm{net}} = \frac{d \vec{L}} {dt} \qquad \text{(system of particles)} \tag{11-29} \end{equation} which is Newton's second law in angular form.  It says  The net external torque $\vec{\tau}_{\mathrm{net}}$ acting on a system of particles is equal to the time rate of change of the system's total angular momentum $\vec{L}$.  Eq. 11.29 is analogous to $\vec{F}_{\mathrm{net}} = d\vec{P}/dt$ (Eq. 9-27) but requires extra caution: Torques and the system's angular momentum must be measured relative to the same origin.  If the center of mass of the system is not accelerating relative to an inertial frame, that origin can be any point.  However, if it is accelerating, then it must be the origin.  For example, consider a wheel as the system of particles.  If it is rotating about an axis that is fixed relative to the ground, then the origin for applying Eq. 11-29 can be any point that is stationary relative to the ground. However, if it is rotating about an axis that is accelerating (such as when the wheel rolls down a ramp), then the origin can be only at its center of mass.


E/UncaughtException: java.lang.NullPointerException: Attempt to invoke interface method 'void mm.com..fragment.BottomSheetFragment$BottomSheetListener.onButtonClicked(java.lang.String)' on a null object reference                            at mm.com.blueplanet.videoclip.fragment.BottomSheetFragment$1.onClick(BottomSheetFragment.java:40)                            at android.view.View.performClick(View.java:5647)   This is RecycervieAdapter class  ((ItemViewHolder) holder).cmtText.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 FragmentTransaction ft = ((DetailActivity) mContext).getSupportFragmentManager()                         .beginTransaction();                 BottomSheetFragment bottomsheet= new BottomSheetFragment();                 bottomsheet.show( ft, "BottomSheet");             }         });   This is bottomsheet  public class BottomSheetFragment extends BottomSheetDialogFragment {   Context mContext;   public BottomSheetListener mListener;    @Nullable   @Override   public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {     View v = inflater.inflate(R.layout.custom_bottom_dialog, container, false);      mContext = getActivity();     ImageButton btn = (ImageButton) v.findViewById(R.id.cmt_btn);     final EditText edt = (EditText) v.findViewById(R.id.edt_cmt);       btn.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View view) {             mListener.onButtonClicked("" + edt.getText().toString());              dismiss();         }     });        return v;   }    public interface BottomSheetListener {     void onButtonClicked(String text);   }    @Override  public void onAttach(Context context) {     super.onAttach(context);     try {         mListener = (BottomSheetListener) mContext;     } catch (ClassCastException e) {         throw new ClassCastException(context.toString());     }   } }

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


#include <iostream> using namespace std;  class A {     public:         int x;     A() {         x=1;         cout << x <<endl;     } };  int main() {     A b();     cout << b.x << endl;     return 0; }   Running this results in compilation error: Error: request for member 'x' in 'b', which is of non-class type 'A()' "cout<< b.x <

Is there any good reason that an empty set of round brackets (parentheses) isn't valid for calling the default constructor in C++?  MyObject  object;  // ok - default ctor MyObject  object(blah); // ok  MyObject  object();  // error   I seem to type "()" automatically everytime. Is there a good reason this isn't allowed?


Given a Finite Field $F$, can the the abelian group $\mathbb Z$ be made into a vector space over $F$ without changing the additive structure of $\mathbb Z$?  This seems like it shouldn't be complicated, but having trouble on this one, any hints would be appreciated.  I already know that $F\cong \mathbb F_{p^n}$ for some prime $p$ and some $n\in \mathbb N$.   I have been trying to make a map $F\times \mathbb Z\rightarrow \mathbb Z$ by $(\overline n,m)\mapsto n\cdot m$ but this really seems like the wrong approach since the axioms aren't really met, maybe its not even possible.  REPLY: Thanks so much for your replies, I am now fairly convinced that there is no such Vector Space. Thank you again, I am very appreciative of your assistance ^_^

This is an exercise from Chapter 3 of Golan's linear algebra book.  Problem: Show $\mathbb{Z}$ is not a vector space over a field.  Solution attempt:  Suppose there is a such a field and proceed by contradiction. I will write multiplication $FV$, where $F$ is in the field and $V$ is an element of $\mathbb{Z}$.   First we rule out the case where the field has characteristic 2. We would have   $$0=(1_F+1_F)1=1_F1+1_F1=2$$  a contradiction.  Now, consider the case where the field does not have characteristic 2. Then there is an element $2^{-1}_F$ in the field, and   $1=2_F(2^{-1}_F1)=2^{-1}_F1+2^{-1}_F1$  Now $2^{-1}_F1\in\mathbb{Z}$ as it is an element of the vector space, but there is no element $a\in\mathbb{Z}$ with $2a=1$, so we have a contradiction.  Is this correct?


So this is going to sound strange, but I'm wondering if there is a clean way to do this.  By the time I have a project done, I will have written two .tex files: one with questions, and another one with solutions. For purposes of peer review, I'd like to know if there's a way for me to use \include so that if each question and solution to each respective question spans only one page, the question and solution will be paired together so that the question is first and the solution is second.  Is there a way (or a better way) to do this beside manually copying/pasting code?  MWE:  Questions:  \documentclass[12pt]{article} \usepackage[margin=2cm]{geometry} \usepackage{enumitem}  \begin{document} \begin{center} \textbf{Mock Exam} \end{center} \begin{enumerate}  \item Here's a question. \begin{enumerate}[label=(\Alph*)] \item Option A \item Option B \item Option C \item Option D \item Option E \end{enumerate} \newpage   \item Here's another question. \begin{enumerate}[label=(\Alph*)] \item Option A \item Option B \item Option C \item Option D \item Option E \end{enumerate} \end{enumerate} \end{document}   Solutions:  \documentclass[12pt]{article} \usepackage[margin=2cm]{geometry} \begin{document} \begin{center} \textbf{SOLUTION} \end{center} \begin{enumerate}  \item (A)  \vspace{0.2cm} -Some stuff telling you why the answer is (A)- \newpage  \item (C)  \vspace{0.2cm} -Some stuff telling you why the answer is (C)- \end{enumerate} \end{document}   This is the general way I have been creating MC exams and solutions in the past for the company, and it's still very early in the project, so I can change the code so that it works if necessary. It's just that I found it very time-consuming to copy-and-paste the solutions into a new file for peer review.

So I have my own layout for my exams based on scrartcl and to prevent anomalies during some changes I want to have only one file per exam which holds both questions/excercises and solutions. Yet I would like to be able to set a variable etc. whichever method might be more convenient so that I can chose for one compilation whether solutions should be visible or not. What is the suggested approach for this?


How do I make a user automatically log in in Lubuntu 16.04?

I want user foo to auto-login using LightDM (which has been used by Ubuntu since version 11.10). How would I do that?


Is it possible to include .x3d, .dae, .pov, .dxf, or .wmf grapics into tex-syntax in order to create a pdf file?

There several types of graphics files. In no particular order .jpeg .eps .pdf .png .tif .jif (and no doubt others). Some work with latex, dvips and some work with pdflatex. How am I supposed to know which?  Just to confuse matters, metapost produces .eps but I can use these with pdflatex as long as I put in a four line incantation.  Can anyone explain this?


All i know is that the top left angle is 80 degrees.

$\triangle ABC$ is an isosceles triangle such that $AB=AC$ and $\angle  BAC$=$20^\circ$. And a point D is on $\overline{AC}$ so that AD=BC, , How to find $\angle{DBC}$?    I could not get how to use the condition $AD=BC$ , How do I use the condition to find $\angle{DBC}$?  EDIT 1: With MvG's observation, we can prove the following fact.     If we set on a point $O$ in $\triangle{ABC}$ such that $\triangle{OBC}$ is a regular triangle, then $O$ is the circumcenter of $\triangle{BCD}$.   First, we will show if we set a point $E$ on the segment $AC$ such that $OE=OB=OC=BC$, then $D=E$.  Becuase $\triangle{ABC}$ is a isosceles triangle, the point $O$ is on the bisecting line of $\angle{BAC}$. $\angle{OAE}=20^\circ/2=10^\circ$.   And because $OE=OC$, $\angle{OCE}=\angle{OEC}=20^\circ$, $\angle{EOA}=20^\circ-10^\circ=10^\circ=\angle{EAO}$.   Therefore $\triangle{AOE}$ is an isosceles triangle such that $EA=EO$. so $AD=BC=AE$, $D=E$.  Now we can see the point $O$ is a circumcenter of the $\triangle{DBC}$ because $OB=OC=OD.$  By using this fact, we can find $\angle{DBC}=70^\circ$,


Im not sure if Im doing something wrong here or what is happening but about 50% of the time whenever I do a normal boolean difference modifier, if I have at all modified the big object previously, I get this instead of a nice clean cut -     Where that bottom cube sticking out was supposed to be cut away. I have no idea what to do about it and oddly a union cuts a hole, but doesn't make the insides have "walls" so to speak. Ive tried recalc normals and everything here   But nothing is working. What is wrong? its doing an additive boolean.

I'm trying to model an , but it's not going so well when it comes to the magazine of the weapon.   Next to the magazine is a mesh. I want to cut holes in the mag with that mesh. But the magazine just goes invisible or connects with the mesh when trying to execute the Boolean Modifier. I have tested to invert the normals and some other stuff, but it isn't working.


I've always heard that black holes are black because light can't escape its intense gravity. If photons are massless how can they be influenced by gravity?  Or is it time that stops (relative to a distant observer) at the event-horizon that prevents photons to move towards the observer?

I understand that a black hole bends the fabric of space time to a point that no object can escape.   I understand that light travels in a straight line along spacetime unless distorted by gravity. If spacetime is being curved by gravity then light should follow that bend in spacetime.  In Newton's Law of Universal Gravitation, the mass of both objects must be entered, but photon has no mass, why should a massless photon  be affected by gravity in by Newton's equations?  What am I missing?


The objective is to print Uni Würzburg using C++  The code I am using:  #include <stdio.h>  using namespace std;  int main() {     char str0[21] = "Uni Würzburg";     printf("%s\n", str0);     char str1[21] = {85,110,105,32,87,'\xc3','\xbc',114,122,98,117,114,103, 0};     printf("%s\n", str1);     char str2[20] = "Uni W\x81rzburg";     printf("%s\n", str2);     char str3[20] = {85,110,105,32,87,'\x81',114,122,98,117,114,103, 0};     printf("%s\n", str3);     return 0; }   I got the \xc3bc from creating a "ü" string and printing the characters.  Output on two different Macs (using both CLion and in bash using g++ test.c -o test):  Uni Würzburg Uni Würzburg Uni W�rzburg Uni W�rzburg   Output on Windows (CLion):  Uni W├╝rzburg Uni W├╝rzburg Uni Würzburg Uni Würzburg   CLion editor and project encodings are in all cases set to UTF-8 and the locale of bash is:  LANG="en_US.UTF-8" LC_COLLATE="en_US.UTF-8" LC_CTYPE="en_US.UTF-8" LC_MESSAGES="en_US.UTF-8" LC_MONETARY="en_US.UTF-8" LC_NUMERIC="en_US.UTF-8" LC_TIME="en_US.UTF-8" LC_ALL=   Why is this happening? Most importantly: What would be a platform independent solution?

I am not able to understand the differences between std::string and std::wstring. I know wstring supports wide characters such as Unicode characters. I have got the following questions:   When should I use std::wstring over std::string? Can std::string hold the entire ASCII character set, including the special characters? Is std::wstring supported by all popular C++ compilers? What is exactly a "wide character"?


If I flip an unbiased coin an infinite number of times, what is the probability that, at some point, the number of heads will be twice the number of tails?  I have already tried making a branching probability tree, but I just get overwhelmed and it seems to go on forever... I don't know how to reconcile it.

I gave my friend  as a brainteaser; while her attempted solution didn't work, it raised an interesting question.  I flip a fair coin repeatedly and record the results.  I stop as soon as the number of heads is equal to twice the number of tails (for example, I will stop after seeing HHT or THTHHH or TTTHHHHHH).  What's the probability that I never stop?  I've tried to just compute the answer directly, but the terms got ugly pretty quickly.  I'm hoping for a hint towards a slick solution, but I will keep trying to brute force an answer in the meantime.


Please note: this is NOT a request to change the reputation required to comment everywhere. Rather, this is a neutral support question asking about the existing limit.  I'm wondering why the minimum reputation required to make comments is set specifically to 50 reputation, and not some other number, like 10, 15, 25, or 100. I'm aware of the FAQ, . But that only explains why there is some sort of a rep hurdle, and not why the limit is set specifically to 50.  In particular, we already trust most users to not spam when they earn 10 reputation (the FAQ cites spam as a reason for the hurdle), and we trust users with 15 reputation to properly cast upvotes and moderator flags, and users with 20 reputation to properly talk in chat. 50 reputation seems like a rather large threshold compared to these.  Also, we've shown that many of the disadvantages outlined in that FAQ post are still gone even with a significantly lower limit, as here on Meta Stack Exchange, one only needs 5 reputation to comment.  Given all of that, why is the number 50 specifically chosen as the minimum reputation required to comment? I asked Shog9 in chat a while ago as to what originally motivated this specific number, and he responded that the limit has been in place since 2008, from before they kept firm logs of discussions. What is the current rationale for keeping the limit as is?

Users with less than 50 reputation points cannot write comments on questions and answers that they don't own.  Why does this limit exist? But I want to contribute now. What should I do instead? But I can't write a good answer without more information! Shouldn't I be allowed to post comments if I have reputation on a different site? But I saw a new user posting a comment! How did they do it? Why do I need 50 reputation to comment on my own post?   See also:    in the Help Center


Very sorry if this is still considered a duplicate to , but unfortunately the answer to this question cannot address this because mine is a nonrigid body and involve biological locomotion concepts Basically, there is an annoyingly curious question asked by my friend (quoted here for reference), which I probably have knew that the answer is false but I lacked the key ideas to explain why  如果有一種生物的體積好像銀河系這麼大 連體積都超越很多很多光年 它爬一爬，就已經不知多少光速的千萬倍? (English translation (brackets are his elaborations)): Say if there exists a lifeform the size of a galaxy, isn't it true that when it moves (e.g. crawl by its limbs), the speed of its movement will be many times of the speed of light c (lightyears of distance in a few seconds as measured in its rest frame)?  =================================================================================== Therefore, instead of asking the above question, I am more interested in the answer to the key element that form this question, which is as follows:  Q1. When we wave our arms in air from point A to point B like a fan, it does look like our entire arm is moving in unison from one point to another. Is the true picture that there is a negligible delay between the movement at the base of the arm and the palm from point A to B, thsat only become significant when the movement approaches the speed of light or the arm is lightyears in length? Q2. Is the principle in Q1 applied to all non rigid bodies, thus whenever it was being moved from point A to point B, it looks like as if the whole thing moved in unison, but in reality e.g. the leftmost side reached point B faster than e.g. the rightmost side?  (PS I don't say "topmost" and "bottomost" side is to avoid the gravitational time dilation factor that might be at play, so that the key confusion and the fundamental mechanism at play can be put into focus) ============================================================================= EDIT2: It was pointed that the answer to Q1 was the same as the answer to the rod However of all the answers in the , only the following seemed to touched on the confusion of Q1  BebopButUnsteady When you move one end of the steel rod, it makes part of it bend and stretch which exerts a force on the next section which makes that move and which makes a new part bend and stretch and so on and so on until you reach Alpha Centauri. This moves along at some speed which is characteristic for the metal which is fast enough that we don't really notice in day to day life. All relativity tells us is that that characteristic speed is less than the speed of light - it turns out for real metal its much less than the speed of light.  Elaboration on Q1: why does the hand looks like it is moving like an unbroken whole? do the combined delay due to the nerve impulse and the sequence of muscle contraction is still not slow enough to caused our arm to look disjointed as each cell in the arm move from one place to another in the waving motion? That is, is the principle mentioned by BebopButUnsteady in the link sufficient to address Q1, or is there other subtleties because of the nonrigid and biological nature of the arm?

Is it possible for information (like 1 and 0s) to be transmitted faster than light?   For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them starts pulling and pushing on his/her end.   The person on the opposite end should receive the pushes and pulls instantaneously as no particle is making the full journey.  Would this actually work?


Prove using induction that for all non-negative integers n and for all integers $ x > 1 $, $ x^n - 1 $ is divisible by $ x - 1 $.  Step 1: We will prove this using induction on n. Step 2: Assume the claim is true when $ n = 1 $. $$ x^{n+1} - 1 = x(x^n - 1) + (x - 1) $$  Can someone help me with this further?

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


Given a vector(an arrow object) say $\vec A\,= \,P \hat{i} + Q \hat{j} + R \hat{k}$ , how to determine the corresponding Euler angles (XYZ) to be assigned to the vector so that it points in that specific direction. Or is there any another way to make that arrow point in that specific direction given by $\vec A$.

I am trying to rotate an object using python, inline with a vector which gives me the direction I want (based on the difference between the last two coordinates of the curve I generated). I therefore have a vector which I'd like to align this object but not the XYZ angles. The options to specify rotation (XYZ Euler...) all seem to require some sort of angle definition. I've started playing with numpy with I'm not experienced enough to find the answer. Would you be able to advise what would be the best way to align an object to a vector and (if necessary) how I could convert the vector coordinates in XYZ_Euler angles I could apply to the object? for instance, Vector=[1,1,1] and I would like to rotate the object along this vector. Thanks for your help  update Thanks guys, DirectionVector.to_track_quat('X', 'Z') did the trick very nicely! #define direction Vector=(1,1,1) DirectionVector = mathutils.Vector(Vector)  #apply rotation bpy.context.object.rotation_mode = 'QUATERNION' bpy.context.object.rotation_quaternion = DirectionVector.to_track_quat('Z','Y')


I have a few files that I accidently updated without making a backup first. I transferred (instead of copying) them to another folder and ended up overwriting the data. Is there any way to restore the files to an earlier point if Volume Shadow Copy isn't enabled?

I just wrote an extensive essay, ironically the last one of my academic career, and then, for the first time in my life, saved over it with an empty document by accident.  Is all hope lost?  Is there any way to restore it to its last version?


I have read a really good answer explaining what -rwxr-xr-x 1 root root 523454 Aug 8 2014  name means.  However, It did not explain the number before the root root. Also, could you explain what lrwxrwxrwx means, please?


Let $A\rightarrow B$ be a ring homomorphism such that $B$ is a finitely generated $A$-module. How one shows that the (set-theoretic) fibers of the map $\operatorname{Spec}B\rightarrow\operatorname{Spec}A$, where the spectra are considered as topological spaces, are always finite?

Let $A$ be a commutative ring with identity and $B$ a finitely generated $A$-algebra that is integral over $A$.  If $\mathfrak{p}$ is a prime ideal of $A$, there are only finitely many prime ideals $P$ of $B$ such that $P\cap A=\mathfrak{p}$.   Let me say that I am aware of  answer, but I can't follow through the hint.  Also, I don't know how to extend to work for algebras rather than extension rings.


This is Sushanta, started familiarizing with Ubuntu Linux. After a successful installation of Ubuntu version 18.04 in my Fujitsu Life book U772 tried to launch Synaptic Package Manager. Unfortunately, It's not opening. I ask for your kind suggestion in this regard as I need to get access to some software like Dropbox and so on.  Please help me out.  Thanks in advance.

I installed Ubuntu 17.10. Now I am having trouble with gksu:  $ gksu -dg synaptic No ask_pass set, using default! xauth: /tmp/libgksu-HgUjgQ/.Xauthority STARTUP_ID: gksu/synaptic/8760-0-alex-XPS-15-9530_TIME4974977 cmd[0]: /usr/bin/sudo cmd[1]: -H cmd[2]: -S cmd[3]: -p cmd[4]: GNOME_SUDO_PASS cmd[5]: -u cmd[6]: root cmd[7]: -- cmd[8]: synaptic buffer: -GNOME_SUDO_PASS- brute force GNOME_SUDO_PASS ended... Yeah, we're in... Unable to init server: Could not connect: Connection refused (synaptic:8767): Gtk-WARNING **: cannot open display: :1 xauth: /tmp/libgksu-HgUjgQ/.Xauthority xauth_env: (null) dir: /tmp/libgksu-HgUjgQ   If I don't use -g, the password dialog is disabled. So looks like a problem with creating a tty for root.  Any advice?


Everytime I'm in the math mode and there already is a \ typed and I type another one, TeXstudio replaces the old one with the new one instead of let me having a \\ typed. This is annoying me and I would like to disable it, but I can't find where to do it. Can someone help?

In general I would like TeXStudio to close my brackets (including {}), but there is always the same problem while using this feature (especially in mathmode): Assuming I want to write something like $\{\hfill\}$ TeXStudio is always ignoring the second \ (because it is overwriting it in the process of typing) and it produces the code $\{\hfill}$. There is obviously a very easy workaround to this problem (by always putting a space after having opened a bracket), but I wonder if there is a way to prevent the second \ to be overwritten (in ALL cases), because I simply do not have any use for this functionality and it is always getting into my workflow and hindering me. I already scrolled through the properties (also the advanced properties), but I haven't found anything useful yet (apart from deactivating the whole "bracket-closing-feature" in auto-completion).  I'd be very thankful for any suggestions.


For example if a High Elf Rogue chooses Ray of Frost for his or her racial cantrip, does that cantrip improve as his or her Rogue level increases? Ray of Frost gets better damage as you advance in level, does it only advance for taking Wizard levels or can any class levels improve racial cantrips?

Cantrips seem to be the only type of spell that cares only about your class level. However, in the multiclassing section they are not mentioned, does this mean that cantrips use your character level, instead of your class level?  Does this mean a Warlock 2 / Fighter 15 can cast an Eldritch Blast with 4 beams just like a level 17 Warlock?


I decided to update my windows 7 install to windows 10, after which my grub was lost. So I used an ubuntu live usb with boot-repair and it found my win10 install. But I no longer have the option to boot into ubuntu. The partitiontable says its in extended space. How do I recover ubuntu? (system= x220 dualboot windows 10 + ubuntu 14.04)

I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?


I took a course of discrete mathematics the last semester. There were some exercises in the book that we used that where really hard, but I did the majority of them. the problem above is one that I have not been able to do. I would like to see the proof so it can help me to solve further problems.  sorry for my english.

Show that the product of any $m$ consecutive positive integers is divisible by $m!$.   Note that we have that $\frac{n!}{m!(n-m)!} \in \mathbb{Z}$ for $0 \leq m \leq n$.  $\require{cancel} \frac{n!}{m!(n-m)!} = \frac{n\cdot(n-1)\cdot\cdot\cdot(n-m+1)(n-m)!}{m!(n-m)!} = \frac{n\cdot(n-1)\cdot\cdot\cdot(n-m+1)\cancel{(n-m)!}}{m!\cancel{(n-m)!}} = \frac{n\cdot(n-1)\cdot\cdot\cdot(n-m+1)}{m!}$ where $n\cdot(n-1)\cdot\cdot\cdot(n-m+1)$ are $m$ consecutive integers divisible by $m!$  Of course, I'm using the fact that I know the combinations formula is an integer but given that, is the proof this simple? Or did I make an error here. Appreciate help!


What are the transfer options for Gothenburg Airport?   The last time I took the airport coaches but they're pretty expensive. GOT is very close to the city center, shouldn't public busses or taxi be an option?

I am visiting Gothenburg in Sweden.  I read on the  that there are buses running between the airport and the city centre (that are not the Flygbuss Airport coaches), but the links there led me to no additional information.  Does anybody know any information about those buses, e.g., the lines, the fares, the timetables, or better, a webpage containing all the information?


I've done as much digging as I know how and I simply cannot find any information on this frame, It has a sticker on the lower referencing a shop called "Helens Bicycles" and as far as I'm aware it was sold for bicycle tours. It has caliper brakes and an older style threaded head. I do know the Rock Shoxs are after market and I'm using the rims the bike came with which match the gear shifter etc (Shimano Deore XT light action)

We often get questions on bicycles.stackexchange about identifying a bicycles manufacturer, model, make, and year.  Often these questions are downvoted or closed -- usually with a comment attached to them that it's not necessary to know the exact model/make/year of a bicycle if you want to fix, repair, or ride your bike. Why should owners not care about the model/make/year of their bicycle? Especially when it comes to less expensive bikes (aka BSOs) and BMX bicycles? This is intended as a canonical question that we can point closed questions to. Also see      (generally not helpful for identifying a brand/model)


I'm using java mail API 1.4.7. Protocol is IMAP. I'm trying to filter messages by using a time period.      Date fromTime = new Date();     Date toTime = new Date();     Folder emailFolder = store.getFolder("INBOX");     emailFolder.open(Folder.READ_ONLY);      //create the search term     SearchTerm term = createSearchTerm(fromTime, toTime);      // retrieve the messages from the folder in an array     Message[] messages = emailFolder.search(term);   Last line of the code trows this exception.  java.lang.NullPointerException   at javax.mail.search.AndTerm.match(AndTerm.java:106)   at javax.mail.search.AndTerm.match(AndTerm.java:106)   at javax.mail.Message.match(Message.java:705)   at javax.mail.Folder.search(Folder.java:1270)   at com.sun.mail.imap.IMAPFolder.search(IMAPFolder.java:1918)   at javax.mail.Folder.search(Folder.java:1231)   at com.sun.mail.imap.IMAPFolder.search(IMAPFolder.java:1873)   etc.  createSearchTerm function  SearchTerm term = null;         ReceivedDateTerm minDateTerm = new ReceivedDateTerm(ComparisonTerm.GE, startTime); ReceivedDateTerm maxDateTerm = new ReceivedDateTerm(ComparisonTerm.LE, endTime);  term = new AndTerm(term, minDateTerm);            //concat the search terms term = new AndTerm(term, maxDateTerm); return term;   Without the search function I can read emails just fine. Can some one help me to find out what wrong with my search function?

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


My problem is that I want me and my friend to be able to play on a survival world together, but we live at different locations. I know I can visit a hosting website but I don't want to pay money because it's just me and my friend. Would there be any way for us to play together without paying any money? My problem is different from that one because we don't want to connect through LAN he is at a different location than me.

I would like to create a minecraft server for me and and my boyfriend to play on.  How do I set it up? Do I need any additional software? Do you have some links to walkthroughs or tutorials?  I have tried to set this up a few times but have failed every time.


The equipartition theorem states that the kinetic energy in a gas of diatomic molecules is equally distributed over all degrees of freedom. So why is the rotation around the molecular axis ruled out (frozen)?

I was reading about the equipartition theorem and I got the following quotations from my books:  A diatomic molecule like oxygen can rotate about two different axes. But rotation about the axis down the length of the molecule doesn't count. - Daniel V. Schröder's Thermal Physics. A diatomic molecule can rotate like a top only about axes perpendicular to the line connecting the atoms but not about that line itself. - Resnick, Halliday, Walker s' Fundamentals of Physics.  Why is it so? Doesn't the rotation take place that way?


currently writing up my report for my uni project and I am unsure if I can accept my hypothesis? My hypothesis is that A and X will have an impact on Y. I have carried out a multiple regression analysis. I have 4 IV’s, A,B,C and D (for ease of explanation) A stands alone and B,C,D are sub-scales to X . The model as a whole appears to be significant p < .001. However, individually the only IV to appear significant is A. B,C,D are not significant p > .o5. Does this mean that I cannot accept my hypothesis, or is it possible to partially accept a hypothesis?? Any help would be amazing, going round in circles here.

I'm aware of several related questions here (e.g., , ) but I don't know the definitive answer for my question below.  Suppose a hypothesis test where we want to test whether a coin is fair or not. We have two hypotheses:  $H_0: p(head)=0.5$  $H_1: p(head)\neq0.5$  Suppose we use 5% significance level, there are two possible cases:   When we obtain the data and find that the p-value is less than 0.05, we say "With significance level 5%, we reject $H_0$."  p-value is greater than 0.05, then we say "With 5% significance level, we cannot reject $H_0$."   My question is:      In case 1, is it correct to say "we accept $H_1$"?   Intuitively, and from what I have learned in the past, I feel that "accepting" anything as a result of hypothesis testing is always incorrect. On the other hand, in this case, since the union on $H_0$ of $H_1$ covers the whole "space", "reject $H_0$" and "accepting $H_1$" look exactly the same to me. On another thought, I can also think of the following idea, which says it is incorrect to say "we accept $H_1$":     We have an evidence strong enough to believe that $H_0$ is not true, but we may not have an evidence strong enough to believe that $H_1$ is true. Therefore, "rejecting $H_0$" does not automatically imply "accepting $H_1$"   So, what is the right answer?


on my site i try to fire and forget with php:  this line starts a process about 20 seconds:  exec('wget -qO- url-to-process' > /dev/null &');   All script is loaded , without attending this line. Now my page is fully loaded. But I have a DataTable, populated with an ajax request. The question is  why ajax request doesn't start until that 20 seconds?  What could be the problem?

I've got a PHP script that needs to invoke a shell script but doesn't care at all about the output. The shell script makes a number of SOAP calls and is slow to complete, so I don't want to slow down the PHP request while it waits for a reply. In fact, the PHP request should be able to exit without terminating the shell process.  I've looked into the various exec(), shell_exec(), pcntl_fork(), etc. functions, but none of them seem to offer exactly what I want. (Or, if they do, it's not clear to me how.) Any suggestions?


I am reading about 'interaction effects on linear regression'  and came across 'stepwise linear regression'.   There are originally 5 predictors in the model. This means to say that by using the ordinary linear regression, we have $ Y = c + a_iX_i$ where $i = 1,...,5$.  Then it says here: For the initial model, use the full model with all terms and their pairwise interactions.  The succeeding steps involve what it calls 'stepwise linear regression'.  I am confused by this statement. Can anyone please give an insight on what 'stepwise linear regression' is all about? What are its advantages and why does it need to be done?

Although the merits of stepwise model selection has been discussed previously, it is becoming unclear to me what exactly is "stepwise model selection" or "stepwise regression". I thought I understood it, but not so sure anymore.  My understanding is that these two terms are synonymous (at least in a regression context), and that they refer to the selection of the best set of predictor variables in an "optimal" or "best" model, given the data. (You can find the Wikipedia page , and another potentially useful overview .)    Based on several previous threads (for example here: ), it appears that stepwise model selection is considered a cardinal sin. And yet, it seems to be used all the time, including by what seem to be well respected statisticians. Or am I mixing up the terminology?  My main questions are:   By "stepwise model selection" or "stepwise regression", do we mean: A) doing sequential hypothesis testing such as likelihood ratio tests or looking at p-values? (There is a related post here: ) Is this what is meant by it and why it is bad? Or B) do we also consider selection based on AIC (or similar information criterion) to be equally bad? From the answer at , it appears that this too is criticized. On the other hand, Whittingham et al. (2006; )1 seems to suggest that variable selection based on information-theoretic (IT) approach is different from stepwise selection (and seems to be a valid approach)...?  And this is the source of all my confusion.  To follow up, if AIC based selection does fall under "stepwise" and is considered inappropriate, then here are additional questions: If this approach is wrong, why is it taught in textbooks, university courses, etc.? Is all that plain wrong? What are good alternatives for selecting which variables should remain in the model? I have come across recommendations to use cross-validation and training-test datasets, and LASSO.   I think everyone can agree that indiscriminately throwing all possible variables into a model and then doing stepwise selection is problematic. Of course, some sane judgement should guide what goes in initially. But what if we already start with a limited number of possible predictor variables based on some (say biological) knowledge, and all these predictors may well be explaining our response? Would this approach of model selection still be flawed? I also acknowledge that selection of the "best" model might not be appropriate if AIC values among different models are very similar (and multi-model inference may be applied in such cases). But is the underlying issue of using AIC-based stepwise selection still problematic?  If we are looking to see which variables seem to explain the response and in what way, why is  this approach wrong, since we know "all models are wrong, but some are useful"?   1. Whittingham, M.J., Stephens, P.A., Bradbury, R.B., & Freckleton, R.P. (2006). Why do we still use stepwise modelling in ecology and behaviour? Journal of Animal Ecology, 75, pp. 1182–1189.


I noticed in the revision history of one of my questions that it said     Tweeted twitter.com/StackMovies/status/etc.   I also noticed that the question was on the Hot Network Questions and was wondering if the fact that it was tweeted meant that it is one of the HNQ's. Does anyone know?

I heard that there was a twitter bot which automatically posted questions and asked for answers for specific questions on every site. How do they work? Is there an algorithm for doing this or is it purely random? I know that it doesn't tweet closed questions, but that's it.


According to the current  (November 2020):  How is a bounty awarded? ... If you do not award your bounty within 7 days (plus the grace period), the highest voted answer created after the bounty started with a minimum score of 2 will be awarded half the bounty amount (or the full amount, if the answer is also accepted). If two or more eligible answers have the same score (their scores are tied), the oldest answer is chosen. If there's no answer meeting those criteria, no bounty is awarded to anyone.  my accepted answer in this question  should have been awarded the bounty but it did not. As you can see in the  the bounty started by the question author at Oct 28 03:23 2 minutes after accepting my answer at Oct 28 03:21. And today after the grace period has ended, the system did not automatically awared any of the bounty, not even the half (200 out off 400 bounty) on a 6 times upvoted answer with the message "Bounty Ended with no winning answer by Community♦". I've got automatic bounties in the past and I know it's working, so, I'd like to know what I'm missing here and what case did this Q/A hit and didn't get any bounty automatically awarded.

It's possible to offer and award bounties of reputation on questions.   What is a bounty? How can I find questions that have a bounty attached? How do I start a bounty? When can I start a bounty? Why is the system requiring me to choose a bounty amount that's higher than the minimum? Can I use Markdown formatting in the bounty remarks? Can I edit the remark? How long is the bounty period? How do I award a bounty? Can I award a bounty to my own answer? Can I award a bounty to an old answer? If I offer a bounty on someone else's question, can I award the bounty to their answer? After awarding the bounty, can I remove it or move it to another answer at a later time? What happens if there's no answer after the bounty period? What happens if I feel my question is still unanswered? What is automatic awarding? Are bounty awards exempt from the 200 points/day reputation limit? How does Community Wiki mode affect bounties? How does user deletion or post dissociation affect bounties? Can I award a bounty to an answer from a deleted user or one where the author was dissociated? Can I offer a second bounty after the first one has expired? Can I raise my bounty? What happens if a bounty question is closed or deleted? Why can't I vote to close or migrate a bounty question? What happens if I delete my account while I have an active bounty? Do I keep an awarded bounty when I delete my answer? What happens if a question where I awarded a bounty later gets deleted or migrated? Can I cancel my bounty? Can I affect / divide / share part of my bounty to two (or more) users? How many outstanding bounties can a single user have?      See also:  in the Help Center


In a formal agreement, we can place one of these two sentences:   He would do sth. He could do sth.   What we want is that if the person, He, wants and is willing to "do sth," he is able to do that and he is not mandated to do it. Which of the above sentences is better in this case?

Possible Duplicate:          I am not a native English speaker and this would/could thing always bothers me. Please give some example + explanation on this. Sorry if the question is too naive.


I am looking for a formula to compute the following:      Assume you are given a GPS coordinate $(\alpha, \beta)=(\text{latitude}, \text{longitude})$ in decimal format (not in the format involving minutes and seconds), a time $t$ and a speed vector $v=(v_x, v_y)$. Now a point moves from $(\alpha, \beta)$ with speed $v$ for the time $t$. The question is: Which GPS coordinate does it end up at (, assuming the earth is a ball with radius $R$)? I am sure there is a formula for that already but I can´t find it. The solution can be an approximation, since I need this for a real world problem. I know that this problem is not strictly well-defined since the speed vector is in Cartesian coordinates, so I am assuming that the earth is locally flat. Still, there should be some almost-solution to my problem, since I am dealing with rather short times and small speed vectors which makes the curvature of the earth almost irrelavant.   Any help will be appreciated!  Leon

Given an initial position and a subsequent position, each given by latitude and longitude in the WGS-84 system.  How do you determine the heading in degrees clockwise from true north of movement?


I have two .css files that I want to merge them. Something like what git dies. All I'm looking for is a tool like git which gets two files as input and generates a file as output which is the merged version of those two input files. Is there such a thing?  For Example: /* file1.css */ .header{     background-color: #f1f1f1;     font-size: 13px; }   /* file2.css */ .header{     background-color: #f1f1f1; } .footer{     background-color: gray;     position: reletive; }   /* expected_result.css */ .header{     background-color: #f1f1f1;     font-size: 13px; } .footer{     background-color: gray;     position: reletive; }

I have a couple CSS files with overlapping CSS selectors that I'd like to programmatically merge (as in not just appending one file to the end of the other). Is there any tool to do this online? or a Firefox extension perhaps?


i am write this code for my android app.      btn =(Button)findViewById(R.id.button);     et =(EditText)findViewById(R.id.editText);     tv =(TextView)findViewById(R.id.textView);      btn.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View v) {             String name =et.getText().toString();             String a = "a";             String a1 = "ａ";             String b = "b";             String b1 = "ß";             if(name.equals(a)){              tv.setText(a1);              }             else if (name.equals(b)){                 tv.setText(b1);              }         }     });  }   }  and write a in edit text don't show ａ in text view and write b in edit text don't show ß in text view please help

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


This started suddenly. Basically i was watching videos on youtube, and suddenly it stopped loading. After a few refresh attempts, it started saying Firefox cannot find the server at ..... Then I tried to google for solution, but even google won't open. My gmail, google maps, analytics, hangouts, basically anything belonging to google has suddenly stopped working. I am even unable to log in this site with my google account, and I am using proxy to post this question itself cause it says "This site requires javascript from a different domain which failed to load" (basically jQuery from the google cdn failed to load). I tried Firefox, chrome, ie, opera and safari all with the same error. All other sites open but none of the google products.  However if I use a proxy, it seems to work. I have tried clearing cache, cookie, offline data, flushing my DNS, and now I have no idea how to get things back to normal. Please tell me if anyone knows of any solutions.  Edit: Ipconfig /all dump->  Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation.  All rights reserved.  C:\Users\Bluemagica>ipconfig /all  Windows IP Configuration     Host Name . . . . . . . . . . . . : Bluemagica-Lapt    Primary Dns Suffix  . . . . . . . :    Node Type . . . . . . . . . . . . : Mixed    IP Routing Enabled. . . . . . . . : No    WINS Proxy Enabled. . . . . . . . : No  Wireless LAN adapter Wireless Network Connection:     Connection-specific DNS Suffix  . :    Description . . . . . . . . . . . : Dell Wireless 1705 802.11b/g/n (2.4GHZ)    Physical Address. . . . . . . . . : 64-5A-04-74-7F-F4    DHCP Enabled. . . . . . . . . . . : Yes    Autoconfiguration Enabled . . . . : Yes    Link-local IPv6 Address . . . . . : fe80::ad7b:a182:5551:4ef9%11(Preferred)    IPv4 Address. . . . . . . . . . . : 192.168.0.101(Preferred)    Subnet Mask . . . . . . . . . . . : 255.255.255.0    Lease Obtained. . . . . . . . . . : Sunday, April 27, 2014 1:35:52 AM    Lease Expires . . . . . . . . . . : Monday, April 28, 2014 1:35:55 AM    Default Gateway . . . . . . . . . : 192.168.0.2    DHCP Server . . . . . . . . . . . : 192.168.0.2    DHCPv6 IAID . . . . . . . . . . . : 358898180    DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-1A-56-07-39-74-86-7A-41-3A-E7     DNS Servers . . . . . . . . . . . : 192.168.1.1    NetBIOS over Tcpip. . . . . . . . : Enabled  Ethernet adapter Local Area Connection:     Media State . . . . . . . . . . . : Media disconnected    Connection-specific DNS Suffix  . :    Description . . . . . . . . . . . : Realtek PCIe FE Family Controller    Physical Address. . . . . . . . . : 74-86-7A-41-3A-E7    DHCP Enabled. . . . . . . . . . . : Yes    Autoconfiguration Enabled . . . . : Yes  Tunnel adapter isatap.{3A63C9DB-C4DE-4D2F-86BE-D946683A7D3B}:     Media State . . . . . . . . . . . : Media disconnected    Connection-specific DNS Suffix  . :    Description . . . . . . . . . . . : Microsoft ISATAP Adapter    Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0    DHCP Enabled. . . . . . . . . . . : No    Autoconfiguration Enabled . . . . : Yes  Tunnel adapter Teredo Tunneling Pseudo-Interface:     Connection-specific DNS Suffix  . :    Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface    Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0    DHCP Enabled. . . . . . . . . . . : No    Autoconfiguration Enabled . . . . : Yes    IPv6 Address. . . . . . . . . . . : 2001:0:9d38:90d7:47:39d7:c4a2:c0f(Preferr ed)    Link-local IPv6 Address . . . . . : fe80::47:39d7:c4a2:c0f%12(Preferred)    Default Gateway . . . . . . . . . : ::    NetBIOS over Tcpip. . . . . . . . : Disabled

I'm  getting timeout errors on google-related sites. If I try to open google.com, gmail.com, etc, it will keep displaying the "waiting reply" on the browser bottom, and the page won't open. If I am browsing another site that includes, say, www.google-analytics.com, ajax.googleapis.com, google fonts, etc, then it start loading, displaying a "connecting to [google-related site]" on the browser bottom, and stall at that point for a long time.  I can browse other sites fine and they load quickly. I can ping the domains with 0% loss and <100ms times. I can ping 8.8.8.8, I am not behind a proxy, there is nothing on my hosts file, I am not at work or in a networked environment: it is a home network behind a router. I connect using wifi (I am too distant to use wired).   Other users on the same network don't have the issue. I can both ping and browse the sites. I have pinged ajax.googleapis.com from my android and my other laptop, and they return the same IP than on this laptop. They also share the same external IP address, according to   The issue happens on ubuntu 12.04, and as it is cyclic but not frequent enough to make sure, I don't honestly remember if it happens on Windows 7 as well (it is a dual-boot machine). Rebooting the router won't help. Rebooting the computer fixes the problem, until it happens again.  It's been happening for a few months now. The last time it happened (earlier today) I performed a ping before and after the reboot. Here's the results:  before  $ping ajax.googleapis.com PING googleapis.l.google.com (74.125.21.95) 56(84) bytes of data. 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=1 ttl=47 time=157 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=2 ttl=47 time=163 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=3 ttl=47 time=156 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=4 ttl=47 time=165 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=5 ttl=47 time=157 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=6 ttl=47 time=155 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=7 ttl=47 time=159 ms 64 bytes from yv-in-f95.1e100.net (74.125.21.95): icmp_req=8 ttl=47 time=157 ms   after  $ping ajax.googleapis.com PING googleapis.l.google.com (74.125.134.95) 56(84) bytes of data. 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=1 ttl=47 time=207 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=2 ttl=47 time=154 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=3 ttl=47 time=154 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=4 ttl=47 time=152 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=5 ttl=47 time=157 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=6 ttl=47 time=160 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=7 ttl=47 time=154 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=8 ttl=47 time=157 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=10 ttl=47 time=154 ms 64 bytes from gg-in-f95.1e100.net (74.125.134.95): icmp_req=11 ttl=47 time=152 ms   The issue happens on different browsers, I installed epiphany and it shows the same behaviour.  I have inspected the network tab on firefox and it shows a single, unreplied GET request:   I installed wireshark and listened for HTTP GET requests; on other sites it pops up on the report, but on ajax.googleapis it shows nothing. I listened then for DNS requests, there are some differences:     If connect via telnet to the port 80 of a random site and perform a GET it works, but I can't telnet to ajax.googleapis.com (or it's IP), the connection never completes.


Several months ago Google Chrome release the most annoying update. Anytime you type the word "google" at the beginning of a search (in the address bar), it hijacks that word and removes it from your search. For example, if I want to search for "google inbox" or "google docs", it changes my search to [Google:] "inbox".    Clearly this feature was designed for very dumb users who think they need to instruct the browser to "google" something rather than just typing their search phrase. I am not a dumb users and do not want the browser hijacking my searches.  I find this endlessly frustrating and cannot for the life of me figure out how to turn this off. Any ideas?

I'm currently using Google Chrome and I run into a problem searching:  Whenever I type something like "Google Chrome" into the address bar, I mean to say, "Search for Google Chrome". However, Chrome by default thinks I'm asking it to Google just the word Chrome.  Any way to disable this, just for the word Google?


Good day! I'm making a game where I need a sprite animation. It's a pretty simple animation but I need to decide what kind of specialist I need to hire to make the animation for me.    This is the sample of the object that I want to animate. I need the core of the object to shoot beams and the shell of the object to be like a blobby-blob, changing its shape constantly, morphing new appendages.  The artist that draw me this sample could make a frame by frame animation. But I wander - may be there is a better way to do that? May be there are some applications that does exactly what I need without all the unnecessary job? I would be thankful for advice!

I have a couple of illustrations done in Illustrator and I am planing to animate it for a website that I am working on, I've heard of  toolkit with flash, but is it the best way to go or is there another "better" way of doing it?  Here's an example of the kind of animations I am aiming for:


I am trying to : Convert all text in a file to uppercase using sed and interested to use range operator. can some one please help me here.  content of Sample.text: unix is great os. unix is opensource. unix is free os. learn operating system. Unix Linux which one you choose.  Thanks in Advance again

My question is how can I convert all text from uppercase to lowercase and vice versa? That is to change the cases of all the letters. It has to be done with a sed replacement somehow.


Let me explain first what I'm trying to do. Because if there's a better way to achieve this, I'm all ears (or eyes actually).  I've built a (html) template parser of sorts. What I can do is write html templates for webpages and include pieces of code from other templates. Something like this:
   %include ads.tmpl bannerad%
     Dis will insert a section (bannerad) from the template file ads.tmpl. And the section in ads.tmpl looks something like this:    <bannerad>

 </bannerad>     That way I can include the same banner code on multiple pages and if I ever want to change the look/feel of the banners, there's only one place I have to chance it. This all works fine.  But now I need to be able to identify where a banner is requested. For obvious reasons, I would like to distinguish between say for instance the top of the home page, and somewhere in between text on a sub page.  My idea was to add some identification to the parent container. Something like this:
   %include ads.tmpl bannerad%
     And then with inline script in the bannercode, iterate through the banners' parentNodes until it finds data-banner_position_id. Something like this:    <bannerad>

    </bannerad>     Now this doesn't work obviously (for several reasons). But is there a way to get this to work? Or is there a better way to do this? It is BTW, completely likely that a page will display more than one banner on a single page...

How can I reference the script element that loaded the javascript that is currently running?  Here's the situation. I have a "master" script being loaded high in the page, first thing under the HEAD tag.  <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <script type="text/javascript" src="scripts.js"></script>   There is a script in "scripts.js" which needs to be able to do on-demand loading of other scripts. The normal method doesn't quite work for me because I need to add new scripts without referencing the HEAD tag, because the HEAD element hasn't finished rendering:  document.getElementsByTagName('head')[0].appendChild(v);   What I want to do is reference the script element that loaded the current script so that I can then append my new dynamically loaded script tags into the DOM after it.  <script type="text/javascript" src="scripts.js"></script> loaded by scripts.js--><script type="text/javascript" src="new_script1.js"></script> loaded by scripts.js --><script type="text/javascript" src="new_script2.js"></script>


$S_{xy} = \sum_{i=1}^n (x_i-\bar{x})(y_i-\bar{y}) = \sum_{i=1}^n x_iy_i - \frac{1}{n}(\sum_{i=1}^n x_i) (\sum_{i=1}^n y_i)$ I don't understand how it becomes $\frac{1}{n}(\sum_{i=1}^n x_i) (\sum_{i=1}^n y_i)$ $S_{xx} = \sum_{i=1}^n (x_i-\bar{x})^2 = \sum_{i=1}^n x_i^2 - \frac{1}{n}(\sum_{i=1}^n x_i)^2$ I also don't understand how the above was expanded.

$$\frac{\sum_{i=0}^nx_iy_i-\bar y\sum_{i=0}^nx_i}{\sum_{i=0}^nx_i^2-\bar x\sum_{i=0}^nx_i}= \frac{\sum_{i=0}^n(x_i-\bar x)(y_i-\bar y)}{\sum_{i=0}^n(x_i-\bar x)^2}$$  Maybe it refers some calculation rules about summation. I cannot solve that. Thanks!


I ran a command      sudo systemctl disable NetworkManager-wait-online.service   to disable the service, but after reboot I still see it in the output of systemd-analyze blame. Also status NetworkManager-wait-online.service returns   ● NetworkManager-wait-online.service - Network Manager Wait Online    Loaded: loaded (/lib/systemd/system/NetworkManager-wait-online.service; disabled; vendor preset: enabled)    Active: active (exited) since Tue 2019-01-01 11:25:48 PST; 44min ago      Docs: man:nm-online(1)  Main PID: 1620 (code=exited, status=0/SUCCESS)

I'm using Ubuntu 18.04.1 LTS. I want to disable network manager on an Ubuntu machine, because (1) I don't need it, (2) I prefer having hardcoded configuration, and (3) network manager regularly causes issues by changing the DHCP configuration. I tried to follow :  Stop network manager sudo systemctl stop NetworkManager.service  Disable network manager (permanently) to avoid it restarting after a reboot sudo systemctl disable NetworkManager.service   Despite this, the network manager is back again every time I reboot the machine. How can I make it go away?


My Users folder and the Windows folder, actually all my files together are suppossedly 123 Gb. The "pie" graphic at Hard Disk properties says, I'm using almost 500Gb. I know there's some people that had a similar problem, but all I found on the web or here, is something like "All my files together make 60 Gb and the pie says I use 75"... I think this isn't my case (in my case it is almost five times a difference!!)

How can I visualize which folders and files are taking up all of the space on my hard drive?  I'm getting some conflicting reports on the size of hard drive contents. Namely what is and isn't there and what folders are actually using the space.   I need to know which of the files or folders the culprits behind all this hidden bloat. Also there should be a print option to get it on paper.


Is it possible to use bind_param in update query where column's name can dynamically changes?  for example  sql='update table_1 set ? = ? where id=?'   In the query above, I want to set the column name also by bind_param, but it causes error.

Why can't I pass the table name to a prepared PDO statement?  $stmt = $dbh->prepare('SELECT * FROM :table WHERE 1'); if ($stmt->execute(array(':table' => 'users'))) {     var_dump($stmt->fetchAll()); }   Is there another safe way to insert a table name into a SQL query? With safe, I mean that I don't want to do  $sql = "SELECT * FROM $table WHERE 1"


I just had my first Composition 102 lecture and the professor said that when you refer to a disease you use "the" as in "the flu."  I don't argue with that example because you say "I have the flu," and not "I have the cold," but if that's true then why does nobody say "the cancer?"  Cancer is a disease, but I have never heard anyone say "the cancer," so is my professor wrong?

Is "flu" the only disease usually accompanied with "the"? From what I understand, you don't usually use "the" with diseases / illnesses / disorders ("have Alzheimer's / diarrhea / claustrophobia / dyslexia, etc." not "have the..."), but it's perfectly normal to say "have the flu". Is the flu the only exception?   Edit (this is only a side part, and can be glossed over if you will, so it's not a duplicate imo): What's so significant about the flu that other conditions don't have, so that it's entitled to "the"?


private void ConvertString(ABC object)  {     String head = "";     String tail="string_tail";     if(!tail.isEmpty())      {         String converter = new StringConvert();         head = converter.convert(tail, TYPE1);         setHeadToTail(head,object);     } }  private void setHeadToTail(String head, ABC object)  {     List<Mixture> values=object.getValues();     if (values!=null)      {         for (Mixture Values1 : values)          {             if (Values1 instanceof NumMixture)              {                 ((NumMixture) Values1 ).setTail(head);             }         }      }   }  I want to write unit test for ConvertString method to check weather the value 'head' converted is equal to the value 'head' being passed in setHeadToTail(). Can anyone help in this?  @Test public void test_ConvertedValue() throws Exception {      ABC obj1=methodToSetSomeValues();     Method method=Project.class.getDeclaredMethod("ConvertString", ABC.class);     method.setAccessible(true);     method.invoke(new Project(), obj1);     String expectedVal= "1234";      ArgumentCaptor<String> argumentCaptor=ArgumentCaptor.forClass(String.class);      verifyPrivate(new Project()).invoke("setHeadToTail", argumentCaptor.capture(), obj1);     assertEquals(expectedVal,argumentCaptor.getValue());   }   In this test case I want to check the value of 'head' converted is equal to parameter passed in setHeadToTail() i.e. head but this is not working.

How do I unit test (using xUnit) a class that has internal private methods, fields or nested classes? Or a function that is made private by having  (static in C/C++) or is in a private () namespace?  It seems bad to change the access modifier for a method or function just to be able to run a test.


class Outer {         class Inner {             }     }  public class Demo {     public static void main(String args[]) {          Outer o = new Outer();         Outer.Inner inner = o.new Inner();          }     }   the way I create a reference for Inner class object is something like accessing static member in Outer class ? could you please explain the mechanism behind this ?

What is the main difference between an inner class and a static nested class in Java? Does design / implementation play a role in choosing one of these?


Is there a word out there describing an overly caring parent? E.g. a mother who is constantly calling her daughter, asking where she is, etc.

I have just finished watching the 3rd season of .  I am wonder whether there is a word for somebody who cares for his/her son/daughter/child too much, like Dr. Cal Lightman?


I try to join my friends server, it says outdated server, got answers? V.1.9

Similar to  on the bugs in Minecraft, I would like a complete list of what error codes exist in Minecraft and how they occur, as well as how they can be resolved.


Greetings Fellow Designers  I want to print a vivid Cyan for a Business Card. Its hex code is #04f1d7. It was sent by my client to me and it was designed in RGB. Now the client is stuck on this option to print, while after converting to CMYK it becomes dull.   But I am getting as image below. Can anyone help me to solve this problem?      but I am looking to catch a straw.

I have a logo that was done with RGB colors, now I have to work with this logo to do something for printing purpuses, the problem is that in the RGB version of the logo I have a shade of green I cannot reproduce with CMYK... How do I do it?   I googled up a bit and found some CMYK values that would create a simmilar green, close enough, the problem is when I put those values in Illustratot(%C %M %Y %K) I don't get the color I am supposed to... what am I missing ?  I have an image to illustrate my problem :    The green I want to create in CMYK is the first green, when I put those values there I get the second green you see there, when I print this image will I get something close to the first green ? ...And this is simply how you view it on screen, a bit darked and washed up ? pom pomm pom pommmmmm  EDIT:  If I open up my logo in Photoshop and go to View > Gamut Warning the green part of my logo shows up in grey, to ged rid of the grey I lower the saturation, the problem is lowering the saturation ruins my nice bright neon green...    EDIT2:  If anyone around here printed neon green, how did you do it ?  I found on some forum someone saying that Pantone 802 C will print neon green, I looked it up, selected it and on screen it looks worse than my second green in the sample image... and anyway, putting a pantone color in a PDF that will be printed on a regular simple printer is any good  ?  [The material the logo will be printed on will be downloaded by various users over the internet in PDF format and will be printed by various home normal hobby printers, so I will not have the control over that at all, I just want a green that will print neon/led green or something closer on a regular hobby printer, not in some fancy color lab/printer. Its imposible isn't it ?]


I wanted to use ffmpeg  ffmpeg -i file.cda file.m4a   but I get the error  Invalid data found when processing input   So how can I convert lots of cda files on macOS?

I have a mac without a disc drive on it, I also have some CDA files on my computer that need to be interpreted into an audio format that is more compatible with modern music programs so that I'm actually able to use them     iTunes is an amazing program to do this with, but it's not letting me import the files into it.  I've tried:   Double-clicking on the files Right-clicking on the files and choosing iTunes to open them with Dragging and dropping the files into iTunes (Even though I was pretty sure that wouldn't work because of the way drag and drop works) Importing the CDA files into Audacity   Also, I'm having some trouble finding another converter online, and since I love the simple design of iTunes, I would much rather prefer to convert the files on there.


In Doctor Who they have said the Master has used up regenerations and started stealing bodies but the only Masters we see on screen are       How many Masters have we not seen? Are theses the only and true Masters in a regenerative cycle and are these the confirmed incarnations of the master?

In the Doctor Who universe, the Master, like the Doctor, is a Time Lord with regeneration capabilities. I know he's been played by several different actors, ranging from Roger Delgado in Old Who to Derek Jacobi in New Who and most recently      Michelle Gomez as Missy   in series 8-9. We have also seen him regenerate on screen at least once (Jacobi -> Simm) and probably more times. But what about regenerations before the first shown in the show, or in between?  In-universe, do we know how many regenerations he has used throughout his life? And therefore how many he has remaining before he finally dies for good the showrunners come up with a way to keep him as a feature of the show (you can't keep a good Who villain down!)      Apologies for the masculine gender. It was partly to avoid spoilers for those who haven't seen Missy yet, and partly because "he/she" sounds clumsy and he has been male almost every time.


What would the best section (if there is one) to ask this question?

I am a college student looking for a mentor and I am not sure how I should go about doing it. I want to post this question but I do not know where to post it or even if this is the right forum for this question.


Let A be a real $ n \times n$ positive definite symmetric matrix.Show that $A=B^2$ for some positive definite symmetric matrix $B$.   So we can try and diagonalize $A$ such that $A=SJS^{-1}$then let $B=S^{-1}\sqrt{J}S $.  But what if one of the eigenvalues of $A$ is "missing" an eigenvector? Our $J$ and $B$ will no longer be positive definite, right?  This addresses an issue that the following answer: , does not address.

Let $A$ be an $n\times n$ positive definite matrix. Show that there exists a unique positive definite matrix $B$ such that $B^2=A$.  I do know the existence. But what about the uniqueness? Would you help me out? Thank you.


How can I construct pairs between elements of a list with no repetition and no omission?   Say I have a list:  tickers = ['SPY','GLD','OIL'].   How can I form an array of pairs?  I want this output:  [('SPY, 'GLD'),('SPY','OIL'), ("GLD','OIL)]

I have a list with 15 numbers in, and I need to write some code that produces all 32,768 combinations of those numbers.   I've found  (by Googling) that apparently does what I'm looking for, but I found the code fairly opaque and am wary of using it. Plus I have a feeling there must be a more elegant solution.  The only thing that occurs to me would be to just loop through the decimal integers 1–32768 and convert those to binary, and use the binary representation as a filter to pick out the appropriate numbers.   Does anyone know of a better way? Using map(), maybe?


In Windows 7, how to make two windows from the same application to be separated in the task bar ?  So when i drag one the other stay in place. For example, opening two windows in Firefox, I want to drag the first to change its position so the second stays in place.  By the way, we didn't have that behavior in Windows Xp !

I mostly like the improvements in Windows 7, but am pretty annoyed with the new Taskbar... particularly its habit of always keeping items grouped.  Is there any way to ungroup the taskbar items in Windows?  And just for the record, "Never combine" does not work.  True, setting this option creates a separate button for each instance of an application... but it still groups all the running instances together.  For instance, all Explorer Windows are grouped together beside each other, and they can only be dragged around as a group---not as individual items.


My Grandad was having trouble logging into his Gmail account yesterday. He managed to find and call the "Google tech support helpline", who claimed to be from Google and claimed that his account has been hacked several times and they needed to remote access into his computer to "clean out the viruses". They also told him to leave his machine on for the rest of the day while they were connected through remote access so they could continue their work.  They said they would call again today to continue the "work" and sort out his issues with logging in to his account and provide him with a bill for their services. I'm surprised they didn't try and bill him yesterday, which makes me think they won't call today and their aim was simply to infect his machine.  Luckily, he contacted me about this and I've told him to leave his computer off for now and not to get in touch with them again.  The question is, what would be the best way to secure his computer now? I expect a simple "Reset Windows" from within his computer won't be enough to ensure that there is nothing malicious remaining on his machine - considering the attackers had remote access.  I believe he upgraded to Windows 10 from a previous version so he doesn't have a licence key - if I reinstall from a clean Windows 10 installer made from another machine, will it recognise his hardware and automatically activate Windows?  There's also the files - he has a large amount of music and photos which would need to be recovered (no backups available). Would an antivirus scan from a Linux machine suffice?

I've been using Windows 10 for a couple of month now (joined the Insider Preview).  Now my hard drive started ticking so I've bought a new SSD and I want to move the windows installation to the new hard drive, which has been connected to the computer (unpartitioned). I don't mind and I even prefer reinstalling it over again.   Since I have the free version of Windows 10 pro, can I still reinstall it anew? Does the windows 10 installation offer disk management and partition like the older Windows installations used to? How should I reinstall Winodws 10 x64 the easiest but still remain on free mode?


I've been trying to find a book I read as a kid. Its about 2 teens (boy and girl) who live on a world where tech is outlawed by a god the people worship called overseer or overwatcher or overthought I can't remember. But they discover that the god is actually an ancient satellite that effects peoples thoughts. They eventually find and board a spaceship and travel to another planet later turning out to be earth way in the future and they were desendant from the humans that left thousands of years ago. They meet two new species of intelligent creatures. One evolved from rats and the other from bats. That's all I can remember. If anyone knows the book please help. Thank you

I'm trying to find a series of stories (a trilogy, I think) with a slew of distinctive features. I can't remember when the books were written (I read them about a year and a half ago), but I can remember several points about the story:  1: It begins in a peaceful city controlled by a matriarchy.  2: Young men and women are tutored in the ways of the world by 'Aunts' and 'Uncles' (who have no actual familial connection).  3: The whole world is actually a colony whose inhabitants are being prevented from developing scientifically by a highly complex mind controlling satellite.  4: The satellite starts to break down, allowing some (including one particularly successful warlord) to fight it's control and develop destructive technologies.  5: The satellite loads itself up with some people (the protagonists) and heads back to Earth for repair.  6: Earth has changed and is now home to two sentient species, one avian ('angels', I seem to recall) and the other subterranean (and fond of sculpture).   7: These two species are in conflict, but are also intricately linked with each other's breeding behaviour.  8: The humans, returned from the colony by the mind controlling satellite, create peace between the two civilisations.  There are so many disparate elements here that I'm beginning to wonder if I just made the whole thing up in a fever dream. Anybody got any ideas?


The code at the end gives    As you can see, \widehat and \widetilde give good result, but \overline looks bad on some characters, especially for A, I and J. What commands or workarounds can solve this problem, please.  \documentclass[10pt, a4paper]{article}  \begin{document}  \noindent $ \overline{A} \ \overline{I} \ \overline{J} $ \\ $ \widetilde{A} \ \widetilde{I} \ \widetilde{J} $ \\ $ \widehat{A} \ \widehat{I} \ \widehat{J} $ \\  \end{document}

One can use \bar to put a bar over a letter in math mode, but often the bar isn't wide enough. An alternative is \overline, but this isn't an accent, so it doesn't take into account the skew of the letter. In the following example, the bar extends too far to the left:    Now the mathabx package offers a \widebar accent, but this has several drawbacks:   mathabx changes a lot of other things, The \widebar sits slightly higher than \bar and \overline, In previewers (checked with kpdf and acroread), the \widebar appears fuzzy, which \bar and \overline don't.   So my question is: How can I put a wide bar over a letter in math mode without the above drawbacks?


I got a PM from a guy on Steam asking personal information. I told him no. He then sent me some code and asked me to "redeem"" the game (represented by the code?).  Is it potentially dangerous if I redeem that code? Will it reveal my personal information?

A user named 'steamfairy1' gifted me a game on Steam. I don't know this user, their profile shows no games, no friends and zero hours played. The profile of 'steamfairy1' was created the day I received the gift.  It very much looks like a scam, but I can't figure out how the scam is supposed to work. What's the worst thing that could happen if I accept the gift? Any idea what the trick here is? It could be just a random act of kindness and I'm just paranoid…  I contacted the Steam support, but they were unhelpful as usual: responding in the wrong language and with a canned one-liner that didn't make a whole lot of sense or had much to do with my question.  Keywords (not really tags, but I want this to be searchable): steamfairy, steam fairy


Will we be able to use python, ruby or other languages to develop apps for Ubuntu tablets and phones?

wrote in  to a question I posted that:      ...the recommended way to develop apps for Ubuntu is the Ubuntu SDK.   So I installed it, but looks like the supported programming language is C++. Does it mean I will need to know C++ to develop a new application for Ubuntu? Is C++ the recommended programming language for Ubuntu application now?  What about Python, I started learning it hoping to develop applications for Ubuntu.


So how far do you need to be to make the mobs despawn?

I understand monsters only spawn in a 9 x 9 grid of chunks centered on the player, and I assume they stay around while they remain within that distance of you. But do they despawn as soon as you move away from them? Or do they remain? If so what (if anything) causes them to despawn? Are the rules any different for passive mobs?  Will running far away from an area and then coming right back clear it of monsters?


I have $A\in \mathbb{R}^{3\times 2}, \ B\in \mathbb{R}^{2\times 3}\;$ such that $AB=\begin{bmatrix} 8 & 2 & -2\\ 2 & 5 & 4\\ -2 & 4 & 5 \end{bmatrix}$ How can I show that $BA=\begin{bmatrix} 9 & 0\\ 0 & 9 \end{bmatrix}$? I tried by bruteforcing systems of linear equations, but it seems too complex.

Let $A∈\mathscr{M}_{3×2}(\mathbb{R})$ and $B∈\mathscr{M}_{2\times3}(\mathbb{R})$ be matrices satisfying   $AB =\begin{bmatrix} 8 &2 &−2\\ 2 &5 &4\\ −2 &4& 5 \end{bmatrix}$. Calculate $BA$. (Golan, The Linear Algebra a Beginning Graduate Student Ought to Know, Exercise 426.)   Maybe it can be solved by solving a system of equations, but I think there is a shorter way since this problem was in my exam.  Thanks.


Prove that $\lfloor 2x \rfloor + \lfloor 2y \rfloor \geq \lfloor x \rfloor + \lfloor y \rfloor + \lfloor x+y \rfloor$ for all real $x$ and $y$.   If anybody could post a simple solution (no complicated abstract theories or calc :D) to the above question, I would greatly appreciate it. Thanks!  Also, if possible, the solution shouldn't wander too much away from floor, ceiling, fraction functions, and other related functions.

Prove that $[2x]+[2y] \geq [x]+[y]+[x+y]$ whenever $x$ and $y$ are real numbers.  The $[]$ symbol is the greatest integer or floor function.  I have proved this fact by cases, but I stumbled upon what I believe to be another way to prove the above inequality, and I was wondering if my sequence of statements are legitimate.  I make use of two lemmas that I have proved  Lemma 1.   If $x$ is a real number and m is an integer, then $[x+m] = [x]+m$.  Lemma 2.   $\displaystyle [x]+\left[x+\frac{1}{2} \right] = [2x]$.  My proof begins with an "obvious" statement   $$x+y \leq x+y+1$$  I then take the floor of the inequality to get  $$[x+y] \leq [x+y]+1$$             (1)  which is true in virtue of lemma 1.   Furthermore, if I add the following statements   $$[x+1/2] \leq x + 1/2$$ $$[y+1/2] \leq y + 1/2$$  I procure  $$\left[x+\frac{1}{2} \right]+\left[y+\frac{1}{2}\right] \leq x+y+1$$  which by definition of the floor function renders the equation  $$[x+y]+1 = \left[x+\frac{1}{2} \right]+\left[y+\frac{1}{2} \right]$$        (2)  Substituting (2) for (1), I have   $$[x+y] \leq \left[x+\frac{1}{2} \right]+\left[y+\frac{1}{2} \right]$$  I then add $[x]$ and $[y]$ to the above inequality to produce  $$[x]+[y]+[x+y] \leq [x]+\left[x+\frac{1}{2} \right]+[y]+\left[y+\frac{1}{2} \right]$$  And in virtue of Lemma 2, the right hand side of the inequality becomes  $$[x]+[y]+[x+y] \leq [2x]+[2y].$$  I personally don't see anything wrong, except maybe for the implication made to establish (2).   Solving these kinds of problems is solely for personal gratification, so I will greatly appreciate feedback.  Thanx.


Trying to update Sharepoint 2013 Visual Studio Workflow with feature upgarde process. Feature upgarde goes well, but no changes are apllied. I can still deploy WF from Vusual Studio 2013 and it redeploys new version without error. But I need to update WF by feature so all running workflows keep going. Any ideas?

I have a question concerning how to manage installation of new versions of workflow features, in case when there are already running instances. It seems on my development machine that after installing new package all running workflows are automatically stopped. It is not a problem now, but how this is going to be handled after deploying to production? Stopping everything after update will surely be problematic.  [EDIT]  I see year ago someone had similar problem, no one knew the solution. Maybe this time it's a bit better?


what is a person called who is always nosing on other people's business - like having a neighbor always outside on the balcony or window to check the neighborhood out.

which adjective can I use to describe my neighbor, who is always trying to keep eye on my personal matters like what am I bringing from market or what am I cooking etc?  Regards,


I would to prove that  $$1+\cos \theta+\cos 2\theta+\ldots+\cos n\theta =\displaystyle\frac{1}{2}+  \frac{\sin\left[(2n+1)\frac{\theta}{2}\right]}{2\sin\left(\frac{\theta}{2}\right)}$$ given that  $$1+z+z^2+z^3+\ldots+z^n=\displaystyle\frac {1-z^{n+1}}{1-z}$$ where $z\neq 1$.  I put $z=e^{i\theta}$. I already got in left hand side cos exp in real part, but there is a problem in the right hand side, I can't split imaginary part and real part. Please help me. Thanks in advance.

I am being asked to prove that $$\sum\limits_{k=0}^{n}\cos(kx)=\frac{1}{2}+\frac{\sin(\frac{2n+1}{2}x)}{2\sin(x/2)}$$ I have some progress made, but I am stuck and could use some help. What I did: It holds that $$\sum\limits_{k=0}^{n}\cos(kx)=\sum\limits_{k=0}^{n}Re(\cos(kx))=\sum\limits_{k=0}^{n}Re(\cos(x)^{k})=Re(\sum\limits_{k=0}^{n}\cos(x)^{k})=Re\left(\cos(0)\cdot\frac{\cos(x)^{n}-1}{\cos(x)-1}\right)=Re\left(\frac{\cos(x)^{n}-1}{\cos(x)-1}\right) $$ For any $z_{1},z_{2}\in\mathbb{C}$ we have it that if $z_{1}=a+bi,z_{2}=c+di$ then $$\frac{z_{1}}{z_{2}}=\frac{z_{1}\overline{z2}}{|z_{2}|^{2}}=\frac{(a+bi)(c-di)}{|z_{2}|^{2}}=\frac{ac-bd+i(bc-ad)}{|z_{2}|^{2}}$$ hence $$Re\left(\frac{z_{1}}{z_{2}}\right)=\frac{Re(z_{1})Re(z_{2})-Im(z_{1})Im(z_{2})}{|z_{2}|^{2}}$$ Thus, $$Re\left(\frac{\cos(x)^{n}-1}{\cos(x)-1}\right)=\frac{(\cos(nx)-1)(\cos(x)-1)-\sin(nx)\sin(x)}{(\cos(x)-1)^{2}+\sin^{2}(x)}=\frac{\cos(nx)\cos(x)-\cos(nx)-\cos(x)+1-\sin(nx)\sin(x)}{\cos^{2}(x)-2\cos(x)+1+\sin^{2}(x)}=\frac{\cos(nx)\cos(x)-\cos(nx)-\cos(x)+1-\sin(nx)\sin(x)}{-2\cos(x)+2}=\frac{\cos(nx)\cos(x)-\cos(nx)-\cos(x)+1-\sin(nx)\sin(x)}{-2(\cos(x)-1)}= \frac{=\cos(nx)\cos(x)-\cos(nx)-\cos(x)+1-\sin(nx)\sin(x)}{-2(-2\cdot\sin^{2}(x/2))}=\frac{\cos(nx)\cos(x)-\cos(nx)-\cos(x)+1-\sin(nx)\sin(x)}{4\sin^{2}(x/2)}=\frac{\cos(nx)\cos(x)-\cos(nx)-\cos(x)+1-\sin(nx)\sin(x)}{4\sin^{2}(x/2)}=\frac{\cos(x(n+1))-\cos(nx)-\cos(x)+1}{4\sin^{2}(x/2)} $$ This is the part where I am stuck, I would appriciate any help or hint on how to continue. Edit: Given the corrections by André I get: $$(\cos(nx+x)-1)(\cos(x)-1)+\sin(nx+x)\sin(x)=\cos(nx+x)\cos(x)-\cos(nx)-\cos(x)+1+\sin(nx+x)\sin(x)$$ so $$\cos(nx+x)\cos(x)+\sin(nx+x)\sin(x)=\cos(xn+x-x)-\cos(nx)=0$$ Edit 2: I found anoter mistake in the above, I will try to correct Edit 3: When multiplying correctly the above it works out :-)


I was reading this  which has the following question,     Linda is 31 years old, single, outspoken, and very bright. She majored   in philosophy. As a student, she was deeply concerned with issues of   discrimination and social justice, and also participated in   anti-nuclear demonstrations.      Which is more probable?      Linda is a bank teller.   Linda is a bank teller and is active in the   feminist movement.   I chose the second option but according to a set theorem the choice was wrong. Why is not possible that linda can be both a bank teller and feminist? What is the simple explanation to this with example?

My professor assigned a completely random question on our problem set. Basically, it goes:  Sophie is 30 years old and majored in philosophy. As a student, she participated in anti-nuclear demonstrations and was deeply concerned with social justice. Which is more probable?  1. Sophie is a bank teller. 2. Sophie is a bank teller and is active in the feminist movement.  I'm guessing the point the prof was trying to get across is that assuming you have two different events $A$ and $B$,  $A\cap B$ would always have a smaller probability than either. Is this correct?


Say you and your friend play a coin toss game where the coin is fair and there is 1/2 chance of winning for each player. What your probability of winning the next game if you have won 5 games and your friend has won 7? What if you have won just 2 games and they have won 9? Note that the first person to win 10 games wins the set.  Please explain in simple terms (like to a five year-old) or to someone with a limited math background how you got your answer.

I'm in a computer algorithms course and have a question about basic probability. My math background includes no more than discrete math and a little calculus, so this probability question left me completely stumped. I checked for similar questions but didn't see any. If this question has been answered already I apologize in advance but I don't even know the correct terms to search to find an answer.  The question goes like this:   Suppose you're playing a set of games and the first to win 10 games  wins the set. Each player has an even chance (1/2) of winning a  game. What is the probability that the first player will win if she  has already won i games and the second player has already won j  games? How do you calculate this for different values of i and j?    Please word the explanation for a non-maths student. I need to provide a recursive formulation for a function that computes this probability then solve it using dynamic programming. No worries on recursion or dynamic programming. I can solve that once I understand how to solve for probability.


The specific situation is the troll is targeted by psychic scream and has his head blown up. So would he somehow regenerate a new head or would this manage to kill him or would he survive but lose all personality and memories? I need to know!

It's a pretty well known fact that trolls can regenerate  lost body parts, provided it wasn't removed by  fire or acid, but can a troll really survive having it's head cut off? I know the rules say any body part, but i think having your brain separated from you and hoping to survive is just pushing your luck. Obviously hydra's and so forth can survive, as they have multiple heads and brains ready to back things up, but a troll normally only has one head.


I am given an old Ubuntu working system and the previous user had everything on his name so started turning it to my name as typing his name everywhere was bugging me. I tried:   $ usermod -l hussain darhamid   This turned the darhamid@darhamid:$ into hussain@darhamid:$  But I want hussain@darhamid:$ also changed to hussain@hussain. What should I do?   I am using ubuntu 12.04

When I connect to my server (ubuntu server 10.10), I get this:  name@server-name.belkin ~>   How can I remove ".belkin"?


E.g.:     "... with all the sustainability considerations that that entails."   If I'm correct, the above example is relative pronoun followed by pronoun - it just happens to be the same word for both grammatically legitimate, albeit adjacent words.  Or, even an example with three that's in a row:     "It wasn't that that that was referring to."   The above sentence may even sound natural in common speech if delivered fluently and in a context in which it was fully understood.  So if one accepts grammatical correctness and one is being clear in it being known what the examples of that are adjuncts for, are repeated that's acceptable after all?

Have you ever had a case where you felt compelled to include strange things like a double that in a sentence? If so, then what did you do to resolve this?  For me, I never knew whether it was acceptable grammar. However, what I did learn was that it was a logic distractor, could lead to confusion, and therefore should be reworded to avoid this.


Where I live, there are hardly any beggars. But wherever I travel (big cities, small cities -- really anywhere) I keep occasionally running into beggars. Now, I do sympathise with these people, but I still feel terribly uncomfortable when I'm approached by one.   What is the best way to "get rid" of a beggar without being outright disrespectful to them? Often I just awkwardly ignore them or tell them I don't have any money with me, but sometimes they are way more persistent than what I'm comfortable with.

I have heard that it is unsafe to show money or help someone in India.  Are there any rules I should respect in order to avoid getting into trouble?  How should I deal with these beggars?


I saw this series incidentally: $$\sum_{n=1}^\infty (\sin n)^n $$ Result from WolframAlpha seems to say the series diverges but I don't know how to prove it. Thanks for any help!

Does the sequence $\{\sin^n(n)\}$ converge?   Does the series $\sum\limits_{n=1}^\infty \sin^n(n)$ converge?


Why is the following wrong?  $ cd "~/my data" bash: cd: ~/my data: No such file or directory  $ cd ~"/my data" bash: cd: ~/my data: No such file or directory  $ cd ~/"my data" # works

According to  and my own understanding, the tilde expands to the home directory:  $ echo ~ /home/braiam   Now, whenever I want the shell expansion to work, i. e. using variable names such $FOO, and do not break due unexpected characters, such spaces, etc. one should use double quotes ":  $ FOO="some string with spaces" $ BAR="echo $FOO" $ echo $BAR echo some string with spaces   Why doesn't this expansion works with the tilde?  $ echo ~/some/path /home/braiam/some/path $ echo "~/some/path" ~/some/path