Question about the relationship between the variance of residuals and variances of the data points

I was reading about regression. I understand one of the how the variance of each $x_i$ needs to be normal distributed, but why doesn't that related to the $s_b$? It seems like it should. I was reading the AP College Board paper about Inference.      Two more assumptions are that the errors are normally distributed and that they have   the same standard deviation for all x values. Although it is not at all obvious, this is   not the same as saying that the residuals are normally distributed and all have the same   standard deviation. The difference is that the “errors” are the deviations between the   response variables and the “actual” underlying (invisible) linear phenomenon, whereas   the “residuals” are the deviations between the response variables and the least-squares   regression line, which is only an estimate of the “actual” line.   I understand (I think) that just because the error of the regression is normal doesn't mean that the variance of $x_i$ is normal because the sample could just randomly follow normality.  (don't know if I said that statistically correct), but if all the $x_i$ are normal and the variance are equal, then why doesn't that variance equal the variance that one would get for the $\beta$  I have gotten some great answers here that are very clear and I am hoping that I could get another answer to help clear up my confusion.    The kernel of my question is What exactly is the relationship between the variance of the residuals and the $x_i$ and is there any connection to the error, variance of $\beta$


Calculate integral using the method of parameter derivation or integration

$$F( \alpha ) = \int^{ \pi }_{ 0} \ln  ( 1 - 2 \alpha \cos x + \alpha^{2} ) dx$$  Should I derive the inner function? But I can't process the derived outcome.


\documentclass[12pt]{report} \usepackage{amsfonts,amsmath,mathtools} \begin{document} \begin{align*} 0\longrightarrow S \xrightarrow{ \begin{array}{c} xyz\\ \end{array} \left[\begin{array}{rrr} 1 \\-1 \\1 \\ \end{array}  \right]  \begin{matrix} \\yz\\xz\\xy  \end{matrix} }S^3 \xrightarrow{ \begin{array}{rrr} yz&xz&xy\\ \left[\begin{array}{rrr} 0&1&1\\ 1&0&-1\\ -1&-1&0\\ \end{array} \right] \end{array} }S^3 \end{align*} \end{document}   I want to align the row yz xz xy with the top row of the 3 by 3 matrix given in the code


I have problem when I implemented this command  sudo apt-get install tcl8.5-dev tk8.5-dev   And I get this:   fawaz@fawaz-Lenovo-B590:~$ sudo apt-get install tcl8.5-dev tk8.5-dev Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  tcl8.5-dev : Depends: tcl8.5 (= 8.5.11-1ubuntu1) but it is not going to be installed  tk8.5-dev : Depends: libx11-dev but it is not going to be installed              Depends: libxss-dev but it is not going to be installed              Depends: libxext-dev but it is not going to be installed              Depends: libxft-dev but it is not going to be installed              Depends: tk8.5 (= 8.5.11-1) but it is not going to be installed E: Unable to correct problems, you have held broken packages. fawaz@fawaz-Lenovo-B590:~$    PLZ help me


How can I make LightDM the default display manager?

I have LightDM installed and can start it with sudo start lightdm. But at boot, GDM is still the default. How can change this so LightDM is loaded automatically at boot instead of GDM?


how to make it to start up like this 'john@john:~/Desktop$ blah blah blah

When I start the Terminal I want it to start up like this john@john:~/Desktop$ blah blah blah without executing the command so I tried to do this sh -c "cd ~/Desktop;blah blah blah; exec bash" but it executed the command.


Indefinite INTEGRAL fraction ( irrational )

$$\int \frac{x-1} {1 + \sqrt{x^2+2x-3}}dx$$ The teacher advised me to calculate through Euler's substitution. Please help me to find the integral  (similar topic was created earlier but now I need Euler's substitution using)


Whitespace Problems With Script and Variables

I'm trying to beat my head against the syntax of this. I'm getting problems with whitespaces and I can't see if there's a better way to do this.  vardir=/home/user cd $vardir for i in $(ls "$vardir") ; do timestamp="$(stat -c %Y $i)" echo "$i" echo "$timestamp"  done   Result is similar no matter where I quote and I'm not sure what I'm doing wrong:  stat: cannot stat ‘Temporary’: No such file or directory Temporary  stat: cannot stat ‘Items’: No such file or directory Items   My goal is I want to grab the timestamps off of backup directories and touch the current ones to restore the original modified dates.


Overflow not beeing recognized, p is not printing warning

I'm having a problem with my little c program.  I'm trying to print out a warning if an overflow occurs, I'm using the limits.h library to recognise an overflow with INT_MAX. I guess the problem is in my if loop, but I can't really find the problem...  #include<stdio.h> #include<limits.h>  int main() {     int x = 1627964;     int y = 9;      for(int i=1; i<y; ++i){         x*= i; // x= x * i         printf("%d * %d \n",x , i+1);         if(x >= INT_MAX){             printf("An Overflow has occured!\n");             return 0;             break;         }     } }   I think the overflow occurs after multiplying with 7:  1627964 * 2 3255928 * 3 9767784 * 4 39071136 * 5 195355680 * 6 1172134080 * 7 -384996032 * 8 1214999040 * 9   I can't really tell why the warning is not printed out...  Some help would be really appreciated, thanks :)


I have initialized an array of size 10 but on printing the sizof array shows  40 . The code is as follows  ,   #include <iostream>  using namespace std;  int main() {     int  arr[10] =  {2,4,5,6,7,8,9,6,90};          printf("%d \n" , sizeof(arr));  }   Output :  /Users/venkat/Library/Caches/CLion2016.1/cmake/generated/InsertionSort-e101b03d/e101b03d/Debug/InsertionSort 40   Process finished with exit code 0   What does C prints 40 here ?


Get Values Using SQL Query Comma Seprated

I have two table like by following   #Table1 Vid  Sid 1     1 1     2 2     3 2     4 3     5 4     6   and  #Table2 Sid  SValue 1    Value1 2    Value2 3    Value3 4    Value4 5    Value5 6    Value6   And I need the output by following like this..  #Output Vid SValue 1   Value1,Value2 2   Value3,Value4 3   Value5 4   Value6   Need SQL Query for the above ouput..


When casting scorching ray must the caster choose his targets first and then roll each ray to determine if they hit?  Or, can they choose one target at a time and see the results of the attack and damage before choosing the next target and ray attack?     Example: Wizard casts scorching ray and there are 3 skeletons.  If the first ray kills the first skeleton can he then aim the other 2 rays at the next one, or does it need to be pre-determined where each ray is going to go?


I am confused with the definition of a primary ideal. The definition states that if $R$ is a commutative ring then $I$ is called a primary ideal of $R$ is the following condition holds. If $xy\in I$ then either $x\in I$ or $y^n\in I$ for some $n$. My confusion lies in the following case. Suppose we have that $xy\in I$ but both $x$ and $y$ are not in $I$ and further $y^n \notin R\  \forall n$. Then by definition we have that $I$ is not primary. However if there exists $k$ such that $x^k\in R$ then the element $yx$ does not lead us to a contradiction. But since our ring is commutative $yx=xy$. So what I don't understand is the following this definition might show me that an ideal turns out to be primary depending on how I write the elements (i.e $xy$ or $yx$) which simply doesn't make sense. So what am I saying wrong here?  Thanks in advance.


"customisation" vs "customization" Which is correct?  As per MS Word, customization is correct but Google Chrome correct it to "customisation"  Thanks in advance.


return statement in finally block good or bad idea

I have write a code here and want to know that, is it good idea to put the return in finally statement? I have put the return statement in finally block because if exception occurred then also it will send the message. So, is this right approach to send the exception message to jsp page or Is their any another way to do it.  public JSONObject SetKeyFunctionDAO(JSONObject obj) throws SQLException      {         DatabaseConnection dc = new DatabaseConnection();         Connection con = dc.openConnection();         JSONObject res = null;         int n ;          String sql = " update data_table set mkey = ? where unique_user = ? and website_name = ? ;";         try          {             PreparedStatement ps = con.prepareStatement(sql);             ps.setString(1, obj.getString("key"));             ps.setString(2, obj.getString("uniqueID"));             ps.setString(3, obj.getString("account"));              n = ps.executeUpdate();             res = new JSONObject();             if(n != 0)             {                 res.put("status", "success");             }             else             {                 res.put("status", "failed");             }         }         catch (SQLException ex)         {            res = new JSONObject();            res.put("status", "failed");            res.put("exception", ex);         }          catch (JSONException ex)          {             res = new JSONObject();             res.put("status", "failed");             res.put("exception", ex);         }         finally         {             dc.closeConnection();             con.close();             return res;         }     }   Thanks in Advance!!


Every time I boot into Windows 10, my network mappings are disconnected

I don't think it's ever not happened.  I'll start an application that depends on the drive being mapped, and it will fail. I'll open windows explorer and see the drive there with the typical red X. It then is clever enough to load the free space on the share - but it still won't actually work until I go into the share in explorer. Then it is mapped correctly.  Is there a way I can either automate that process every startup, or even better, actually have my drives map properly?


How do you use /title? I used it like this   /title @a title {text:"you're fighting the castle",bold:true,italic:true,color:red}"    and it gave me this error      [10:51:17] Invalid json: malformed JSON at line 1 column 3    I'm trying to make something and I've been stuck for a while so if anyone knows please help me!!!


Is $f(x,y)=\frac{xy^3}{x^2+y^6}$ differentiable at $(0,0)$?

Is the following function differentiable at $(0,0)$? $$ \  f(x,y) =   \begin{cases}    \frac{xy^3}{x^2+y^6} & \text{if } (x,y) \ne (0,0), \\    0       & \text{if } (x,y) = (0,0).   \end{cases} $$ I found that both of the partial derivatives are $0$, and then tried to calculate the following limit: $$\lim_{(x,y) \to (0,0)} \frac{\frac{xy^3}{x^2+y^6}}{\sqrt{x^2+y^2}} = \lim_{(x,y) \to (0,0)} \frac{xy^3}{(x^2+y^6) \sqrt{x^2+y^2}}$$ And then I got stuck. I tried the squeeze theorem, but I still couldn't calculate it. How can I calculate this limit?


Unable to enter new commands in terminal -- stuck with ">"

No matter what I do I'm stuck with >. How can I enter a new command?  $ chmod -R 600 `/ .ssh >  > chmod > id_rsa.pub >  > sudo chmod 600 ~/ssh/id_rsa     I was trying to sync the master and slave by following a youtube video when I encountered the "permission denied" issue. While trying to resolve it I got stuck with >. Now I can't enter any new command.   Please guide me. I'm a Linux/AWS newbie.


3 years ago I went volunteering and brought back this weird USB cable and in those 3 years i never could figure out how to use this USB cable and what is the purpose of its disposition. So... what do you use this cable for (I think those are 3 USB 2.0 connectors - I don't know how to differenciate USB 2.0 and older USB's...) ?


un-installing a microwave that does not have any visible top cabinet attachment

I want to uninstall a Hotpoint model RVM1335 over-the-range microwave.  I thought I'd take it easy; so, I purchased installation and cart-away.  When the Home Depot delivered the replacement, they didn't know how to uninstall the old microwave; so now, the new one sits on my living room floor.  I found the installation instructions online for the existing oven. There is a paragraph on uninstalling it; but, they assume that the microwave was attached to both the back wall and the upper cabinet [like most.]  There are no [visible] screws or bolts either to the upper cabinet or to the cabinets on each side; only a hole for the power cord.  I "inherited" this in a home purchase; so, there's no one to ask.   Has anybody seen this before?


Every which way I try to correct unmet dependencies it gives me some long error. Trying to install packages I get   evas-loaders : Depends: libefl (>= 201312241217) but it is not going to be installed libedbus1 : Depends: libefl (>= 201312241217) but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   If I try to open software-proporties-gtk its a grey icon that cannot be opened. Trying Synaptic package manager to fix broken packages evas-loaders/libedbus1 it says   Failed to fetch http://packages.enlightenment.org/ubuntu/dists/jaunty/Release.gpg Something wicked happened resolving 'packages.enlightenment.**org:http' (-5 - No address associated with hostname)   and another thirty something like that.


Find uninstalled aptitude package which provides command

What's the best way to find the uninstalled aptitude package associated with a command? I'm aware of apt-file but it's output is usually hard to parse.  For example, apt-file search ifconfig outputs 45 results. I could probably use some regex to reduce that even more, but that's far from ideal.  I'd like to be able to do something like findpkg ifconfig and see net-tools without clutter.


Are commuting endomorphisms polynomials of a same (third) endomorphism?

Let $E$ be a finite dimensional $k$-vector space ($k$ may be assumed algebraically closed if needed) and $u,v \in \mathcal L(E)$ be two endomorphisms that commute ($u\circ v=v \circ  u$).  Does there exist a third endomorphism $w$ and two polynomials $P,Q\in k[X]$ such that $u=P(w)$ and $v=Q(w)$?  I think the heart of the problem is to deal with the nilpotent subcase (where u and v are supposed to be both nilpotent). If $u$ (or $v$) is cyclic (ie only one Jordan block) this is classical, but I am not sure how to deal with the general case...


Show that exists $m, n \in \mathbb{Z}$ such that $|m+n \sqrt{2}|<\frac{1}{10}$.

Show that there exists $m, n \in \mathbb{Z}$ such that $$|m+n \sqrt{2}|<\frac{1}{10}$$. Try assuming that there are no $m$ and $n$ that satisfy the inequality Then, $|m+n \sqrt{2}|\geq \frac{1}{10} \forall m,n \in \mathbb{Z}$ Then $\frac{1}{10}$ is a lower bound of  {$|m+n \sqrt{2}|$ for $m,n \in \mathbb{Z}$} but here I'm stuck and I don't know what to do next!


EDIT: Why is $\sum_{k=1}^n \frac{1}{\sqrt{k}}>\sqrt{n}$?

Having problems with another inductive proof.. again with the algebra  $$\sum_{k=1}^n \frac{1}{\sqrt{k}}>\sqrt{n} :\ \forall n\in\mathbb{N}, n>1$$  What I've done:   Proved for n=1 Showed I need to prove $$\sum_{k=1}^{n+1} \frac{1}{\sqrt{k}}>\sqrt{n+1}$$ Attempt: $$\sum_{k=1}^{n} \frac{1}{\sqrt{k}}+\frac{1}{\sqrt{n+1}}>\sqrt{n}+\frac{1}{\sqrt{n+1}}$$ $$\iff \sum_{k=1}^{n+1} \frac{1}{\sqrt{k}}>\sqrt{n}+\frac{1}{\sqrt{n+1}} $$   Again, I come no futher than this. I assume its something I don't know or can't see.  Cheers!  Andy  Edit: After being referred to another similar question, what I don't understand is why  $$\sqrt{n}+\frac{1}{\sqrt{n+1}}>\sqrt{n+1}$$ which it obviously must be.  In the same vein, during my proof I didn't know (algebraically) to prove  $$\sum_{k=1}^n \frac{1}{\sqrt{k}}>\sqrt{n}$$   If I put numbers in I can see that it is trivially true but not why it is generally true..


Ubuntu based distro with slim storage footprint

I am looking to install Linux on a new laptop I have, with only 64gb of storage.  I am curious if there are any sources that compare the base install size of various distros.  I am not looking to go off the beaten path, so I am really only considering maybe Lubuntu, Xubuntu, or Ubuntu Mate. I might consider Ubuntu 18.04 with minimal install, but I only have 4gb ram as well, so I rather avoid gnome.  Is there any hard data (besides recommended storage size) that I can look into?


Evalute the definite integral: $\int_{0}^{3} (x^2+1) d[x]$

Evalute  the definite integral:     $$\int_{0}^{3} (x^2+1) d[x]$$   $[x] -$ is integer part of the $x$.  Is the solution correct?


Is it possible to run two windows sessions from the same computer at the same time?

A friend asked me if it is possible to have two screen/keyboards/mouse connected to one computer, and allowing two users to use the computer as if they where using two different computers (one sessions for each input/output)  Is it possible?


Kessel Run in 12 parsecs: screenplay error, or part of the movie?

I know this has been a long debated question among Star Wars enthusiasts, but when Han Solo said that he made the Kessel Run in 12 parsecs did he actually know what he was talking about?  During the scene Han really does seem to be talking about the time it took him to make the run.  When he is talking to Obi Wan he is trying to persuade him that the Falcon is the fastest ship in the Galaxy, but if he were truly referring to the distance he made the run in, it would be more referring to his pilot skills, not the ship's speed.  Could it have been that he just misspoke, or was his "I made it in 12 parsecs" really referring to the distance of the run.  This  agrees with the latter of the two:     Solo was not referring directly to his ship's speed when he made this claim. Instead, he was referring to the shorter route he was able to travel by skirting the nearby Maw black hole cluster, thus making the run in under the standard distance.   All of the contradicting pieces of evidence have made me wonder:   Did Han know what a parsec was? Was he just trying to impress Obi Wan with big words, not knowing who he was talking to? Was it an error in the screen play?


I receive a date that i want to check if it is not in the right format (dd/MM/YYYY), I add an error to display, knowing my date is of type localDate. I found a lot of code to how to validate string dates but not localdate, if any one has an idea: Here is what I did for the moment and It is returning all dates even in the right format LocalDate mydate; final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/YYYY");  try {           String date = myDate.format(formatter);         LocalDate.parse(date, formatter); }  catch (Exception e) {       errors.add(....)); }       Thank you


How does google maps know that I've taken pictures?

Yesterday I've visited a restaurant. The restaurant had a beautiful garden and colorful plants. So I took several pictures there. Today, Google Maps sent me a notification and offered me to share those pictures as I've taken for that restaurant.  How does Google Maps know that I've taken pictures there? Does the app regularly check(while the app is running) my pictures and their location without my knowledge? If so, then Google Maps can also upload those pictures to somewhere without even asking me? So if I allow access to my photos for an app, does that mean the app can access my photos without showing a "BROWSE" or something like that and upload to somewhere? I though iOS API needs photos to be picked by user to be shared by an app. Otherwise any app that has proper access permissions can access to all of my photos and then may upload all of them to cloud, whithout my knowledge, right?  Edit: Ok, I'm having hard time to explain myself. I know if Google Maps has access permissions to photos, then it can access photos. That's not the issue here. The problem is that: My phone is locked and sitting on the table. Then I get a notification from Google Maps, asking to share the photos I've taken yesterday at the restaurant I've visited! Not only that, when I click the notification, Google Maps opens up with a view with already selected photos which all taken at the specified location. This is only possible if I opened the Google Maps app, after taking photos, which I did for getting back to home. The problem is, when I open the Google Maps or any other app that has access permission to photos, does this mean all those app can access all of my photos, any time(if app is running in foreground)? I thought apps need to call some iOS APIs to show me the thumbnails, then only the photos I've checked will be delivered to app. That is, I thought apps can only access the photos I've picked from the thumbnail view and the thumbnail view is mandatory and handled by iOS, just like passcode and touchID(apps can't read users' fingerprint or passcode, it's all handled by iOS).


Is "recommend deletion" secretly a vote to delete?

There's a  (attributed to Shog9 but not verifiable by me) that     If six users without the ability to delete "recommend deletion", the post will also be automatically deleted.   If this is true, I find it worrisome. It creates a parallel vote-to-delete that users between 2000 and 20,000 rep can vote in, even if some of these users are not even trusted to vote to close.  What's more, these users are presented with the choice in a way that stongly encourages them to vote for deletion, in that the only alternatives (apart from "don't know") is "looks good" and "edit it to look good". This suggests to users that if they understand the question and the answer (and so "don't know" is not right), there is no middle ground between answers that "look good" (or can be made to do so) and answers that ought to be deleted. In effect the UI is suggesting that unless the user would upvote the answer, he should vote for deletion -- even though the vote is presented to him as a "recommendation".  It feels very backwards to encourage users to vote to delete by making it free, whereas merely downvoting an answer costs 1 rep.  At least at Math.SE we have a significant population of answers that are not good answers, but nevertheless shouldn't be deleted -- downvotes are the right way to deal with them. These answers are often short enough to trigger the low-quality filter. Their major characteristic is that they often embody the first instinctive reaction of somebody looking at the question, but are actually wrong for subtle reasons explained in comments or other answers. Having them stay visible but downvoted conveys valuable information to the reader, namely that this intuitively "obvious" answer is in fact wrong. Deleting them would entail a loss in usefulness.  If the secret parallel deletion vote is real, I think that   It should be made much more obvious to the user casting the "recommendation" that such a recommendation is in fact a vote that will cause automatic deletion without being reviewed by a moderator or high-rep user. The review interface really should provide a middle way between "looks good, I will upvote" and "burn it with fire!", such as "no action is needed" or "downvoting is good enough for this".


Workspace stays fixed on external monitor when switching workspace

Im using ubuntu 11.10, running, and loving, the gnome3 interface.  I am running an optimus enabled laptop with bumblebee.   i just figured out how to put the top panel on my external monitor (connected via VGA), which therefore makes my external my 'primary' monitor (a.k.a thats where all the action happens). However now i notice that when i switch workspaces, only the external monitor switches, my laptop screen remains in a fixed workspace.  It should be noted that if move the top panel back to my laptop screen, the problem reverses in that the workspace on my external monitor remains fixed when switching workspaces, i just didn't notice this before.  Is there any way to get my laptop screen to switch as well?  Thank you


I can't use any GRASS tool, I get the error "The following layers were not correctly generated"

I've been trying to use GRASS r.fill.dir to get a filled DEM but I get the error:  The following layers were not correctly generated.   I tried using SAGA Fill Sinks, that worked. I get the same error on every GRASS tool I use.  QGIS version 3.12.0-București


Are there any ways to embed LaTeX source code from a PDF file

I want to the tex files from PDF files.  I have the PDF files that I get in Internet and have a lot of mathematics,  so I want to convert PDF files into tex files.  I researched in these forum, and  following links may be related ,but I couldnt understand clearly.    Please teach me are there any ways, or teach me how to use.  Thank you.  January,3rd i added. What i want is OCR,not embedded. i want pdf or images to detect the text words into tex.


ExecuteError: Failed to execute. Parameters are not valid error when SelectLayerByAttribute run in Python 2.7

I am running a line of code in a Python 2.7 environment using arcpy.SelectLayerByAttribute_management:  fl_haz_selects = arcpy.SelectLayerByAttribute_management(S_Fld_Haz_Ar, "NEW_SELECTION", "\"DFIRM_ID\" = '{}'".format(fipC))   It runs perfectly fine in Python 3.6. Now I am getting the following errors. What am I doing incorrectly here? Note: S_FLD_Haz_Ar is a shapefile. Do I just need to make it into a layer? I am trying to avoid making a physical layer.     Traceback (most recent call last):   File "", line   3, in    File "C:\Program Files   (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\management.py", line 7713, in   SelectLayerByAttribute       raise e ExecuteError: Failed to execute. Parameters are not valid. The value cannot be a feature class ERROR 000840: The value is not a   Raster Layer. ERROR 000840: The value is not a Mosaic Layer. Failed to   execute (SelectLayerByAttribute).


Android :how to display all users in firebase database except one

Here is my Model. I want to display all users except "peter". Here is my code:          //iterating through all the values in database             for (DataSnapshot postSnapshot : snapshot.getChildren()) {                 User user= postSnapshot.getValue(User.class);                 if (user.getUsername()!="peter"){                 users.add(user);}             }             //creating adapter             adapter = new MyAdapter(getApplicationContext(), users);              //adding adapter to recyclerview             recyclerView.setAdapter(adapter);   problem: my list still displays the user Peter!!


When are data posted to Stack Exchange Data Explorer? What is the frequency of data being posted to Stack Exchange Data Explorer?


Following Sunday based on date in LibreOffice Calc

I'm looking to create a calculation to display the following Sunday in day-month format based on the current date (=NOW()).  How can I do that?


Prove this function is differentiable at a point but the partial derivatives are not continuous

Let $f:\mathbb{R^2} \rightarrow \mathbb{R}$ be a function defined as \begin{align*} f(x,y) =       \begin{cases}        (x^2+y^2){\sin\left(\frac{1}{\sqrt{x^2+y^2}}\right)} &\quad\text{if } (x,y) \ne(0,0) \\        0 &\quad\text{otherwise.} \\       \end{cases} \end{align*}  Prove that $f$ is differentiable at $(0,0)$ but its partial derivatives aren't continuous at $(0,0)$.    For the first part, I proved it by definition of differentiability at that point. So, I want that  \begin{align*} \lim_{(x,y)\to\ (0,0)} \frac{f(x,y) - f(0,0) - \frac{\partial f}{\partial x}(0,0)x - \frac{\partial f}{\partial y}(0,0)y}{\Vert (x,y) - (0,0)\Vert} = 0 \end{align*}  By definition, $f(0,0) = 0$. Then i calculate $\frac{\partial f}{\partial x}(0,0)$ and $\frac{\partial f}{\partial y}(0,0)$:  \begin{align*} \frac{\partial f}{\partial x}(0,0) = \lim_{h\to\ 0} \frac{f(h,0) - f(0,0)}{h} = \lim_{h\to\ 0} \frac{h^2\sin\left(\frac{1}{\mid h \mid}\right)}{h} \leq\lim_{h\to\ 0} \frac{h^2}{h} = 0 \end{align*}  \begin{align*} \frac{\partial f}{\partial y}(0,0) = \lim_{h\to\ 0} \frac{f(0,h) - f(0,0)}{h} = \lim_{h\to\ 0} \frac{h^2\sin\left(\frac{1}{\mid h \mid}\right)}{h} \leq\lim_{h\to\ 0} \frac{h^2}{h} = 0 \end{align*}  And,  \begin{align*} \lim_{(x,y)\to\ (0,0)} f(x,y) = \lim_{(x,y)\to\ (0,0)} (x^2+y^2)\sin\left(\frac{1}{\sqrt{x^2+y^2}}\right) \leq \lim_{(x,y)\to\ (0,0)} (x^2+y^2) = 0 \end{align*}   Then the limit is 0 so f is differentiable at $(0,0)$. To prove the partials aren't continuous, I calculate $\frac{\partial f}{\partial x}(x,y)$ using derivative rules around $(0,0)$:  \begin{align*} \frac{\partial f}{\partial x}(x,y) =      \begin{cases}        2x\sin\left(\frac{1}{\sqrt{x^2+y^2}}\right)-x\frac{\cos\left(\frac{1}{\sqrt{x^2+y^2}}\right)}{\sqrt{x^2+y^2}} &\quad\text{if } (x,y)\ne(0,0) \\        0 &\quad\text{otherwise.} \\       \end{cases} \end{align*}  Which i have to prove is not continuous but I can't find the right curves to accomplish this. Any suggestions?


how to print values in console using scriplet in javascript while a function is called

How to print values in console (like System.out.println() in java) using scriplet in javascript while a function is called ? if i used System.out.println("test") in scriplet the values is getting printed while a jsp form is loading but i want it to print only when a java script is called.


How do i prove if this is true or false?

Is $\mathcal{P}(A\cup B)=\mathcal{P}(A)\cup\mathcal{P}(B)$ true for all sets $A$ and $B$?  If so, prove it.  If not, give an example of sets $A$ and $B$ for which it is false and show why it is false for these sets.


First x tick tabel is not shown when using xticklabels from tabels


Problem with UV unwrap, collapsing vertices

I am somewhat new to modeling but I have done uv's a few times before, but for some reason, I can't get it to work right this time. I have marked seams and set up a blank texture but when I unwrap (using the basic "unwrap") it comes out really strange, with most of the islands being a diamond shape.(Edit) I have deleted all seams and started from scratch and the same problem persists so it cant be from modifying the mesh after the uv is made. ]


Can a character purposefully delay his position in the initiative order?

Many actions in combat (like making an enemy fall prone), can give an edge to your teammates (in this case, melee advantage) until the enemy's turn (in this case, he would get back up to end the condition). Such actions are the most useful when your turn is right after the enemy's turn, so that all of your teammates can benefit from the edge you give them.  Contrary to the Ready Action (which enables to delay an action to be made after a specified trigger), what I'm seeking here is for a character to delay his entire turn in the initiative order. Is such a thing possible ?  Example 1 : The initial order is Bob, Enemy, Friend 1, Friend 2. Bob wants to delay his turns in the initiative order to do as if his initiative roll had placed him right after "Enemy" in the cycle : Enemy, Bob, Friend 1, Friend 2.  Example 2 : The initial order is Friend 1, Friend 2, Bob, Enemy. Bob wants to delay his turns again, even if, this time, he won't do anything for the first round. The second round's order would then be : Bob, Friend 1, Friend 2, Enemy.


I have asked this on CS subsite but since there was no reply yet and the question is also somewhat related to physics, I think it will be appropriate to post here as well.  Landauer's principle states the minimum possible amount of energy required to erase one bit of information is $k T \ln 2$   How is this formula found? In terms of energy and memory unit, what is the processing cost per bit for normal and reverse operations respectively?


What terminal is this and from where do I get such a beautiful terminal on Ubuntu?


How to raise desktops without clicking on "Activities"

I've searched and not found this question.  Long time Ubuntu user, and the last several years a Gnubuntu user (and happy about the switch to Gnome).  HOWEVER, how in the world do I get Activities to raise the desktops by just sending my mouse pointer to the upper left hand corner of the screen (like I used to do in Gnubuntu)?  Having to click on "Activities" to do this is really slowing me down.  I know, first world problems, but this is driving me batty.  Thanks.  Brand new Ubuntu 18.04 install, not an upgrade over 16.04.


How to check for nulls in a deep lambda expression?

How can I check for nulls in a deep lamda expression?  Say for example I have a class structure that was nested several layers deep, and I wanted to execute the following lambda:  x => x.Two.Three.Four.Foo   I want it to return null if Two, Three, or Four were null, rather than throwing a System.NullReferenceException.  public class Tests {     // This test will succeed     [Fact]     public void ReturnsValueWhenClass2NotNull()     {         var one = new One();         one.Two = new Two();         one.Two.Three = new Three();         one.Two.Three.Four = new Four();         one.Two.Three.Four.Foo = "blah";          var result = GetValue(one, x => x.Two.Three.Four.Foo);          Assert.Equal("blah", result);     }      // This test will fail     [Fact]     public void ReturnsNullWhenClass2IsNull()     {         var one = new One();          var result = GetValue(one, x => x.Two.Three.Four.Foo);          Assert.Equal(null, result);     }      private TResult GetValue<TModel, TResult>(TModel model, Expression<Func<TModel, TResult>> expression)     {         var func = expression.Compile();         var value = func(model);         return value;     }      public class One     {         public Two Two { get; set; }     }      public class Two     {         public Three Three { get; set; }     }      public class Three     {         public Four Four { get; set; }     }      public class Four     {         public string Foo { get; set; }         public string Bar { get; set; }     } }   UPDATE:  One solution would be to catch the NullReferenceException like this:      private TResult GetValue<TModel, TResult>(TModel model, Expression<Func<TModel, TResult>> expression)     {         TResult value;         try         {             var func = expression.Compile();             value = func(model);         }         catch (NullReferenceException)         {             value = default(TResult);         }         return value;     }   But I hate to incur the expense of catching an exception that is not, in my mind, exceptional. I expect this to be the case quite often in my domain.  UPDATE 2:  Another solution would be modify the property getters like this:      public class One     {         private Two two;         public Two Two         {             get             {                 return two ?? new Two();             }             set             {                 two = value;             }         }     }   Which is mostly ok for my domain, but there are times when I really to expect a property to return null. I checked the answer from Josh E as helpful since it comes pretty close to what I need in some cases.


led resistor calculation, and resistor wattage?

I know this has been asked time and time again but bear with me as I am struggling to understand, so say I have this simple circuit here   with 120v (dc for simplicity) as the input voltage and I have an led that runs on 3.4v and max 20ma ohms law states I=V/R so R=V/I, so R=120v/0.02a = 6000 ohms or 6k is this correct? how do I know the voltage drop across the resistor is correct, and what about power dissipated by the resistor? also, Is there an easy way to calculate everything at once?


Can you please tell me how to get the party girl and what she sells for how much?


Today the commands in the terminal start with "public-docking-hg-2434:~ userName$"  What is this public-docking-hg? Why did it suddenly appear?


how can I remove the clear screen before login

On ubuntu server, how can I avoid the screen being cleared just before the login screen pops?  I'm trying to read an error message on one of the services and I get this annoying clear screen and I cannot scroll up with shift-pageUp.


Remove the end time of bounties from question titles?

So today I chimed in on IPS and scrolled a bit. This question caught my eye, because it had a number in it.     Something like that I haven't seen in a long time, if ever. Then I read the title and was confused at first, because it started with      ends in 4 days How do I...   This is obviously not proper English. It took me some time to realize that the text size isn't even the same, because the difference is very little in my opinion.   Also, I don't see any reason why that text is necessary in the title.    It gives no additional incentive to answer the question It seems like it's part of the question title It's already obvious that the question has a bounty The time until a bounty runs out is already visible inside a question   This update looks better or worse depending on the site style, but overall I think that it's not something that is needed and has more drawback than it adds.  So I am wondering why this text has been added in the first place and if it can be removed again? Perhaps a per-site solution is possible. I am open to discussion about it (mostly interested in what that text adds to the user experience).


When a user has one of their questions or answers deleted, why don't you notify them about the deletion, and send the removed content by email?

Some questions or answers can take a while to write.  For example, I had written a question on , and one day it got silently deleted, meaning I cannot access it any more (luckily I had a backup, without all the links that used to be though).   Why don't you notify the author about the deletion, and send the removed content by email? I find that removing content and leaving no access to it without warning is highly disrespectful to the people who took the time to write it.  Here is the question I had asked that got removed. As you can see, it would have been painful for me to re-write the whole question if I hadn't saved it:     Question: Are there any recent results on the performances of head   tracking devices used to move the mouse cursor in comparison with   traditional mice? (e.g. using Fitts's law)      Question's details: As I use a head tracking device to move the mouse   cursor for efficiency purpose, I was curious to know whether the   Fitts's law can be applied to it (i.e. is not restricted to hands).   Fitts's law says "Fitts' law has been shown to apply under a variety   of conditions, with many different limbs (hands, feet, head-mounted   sights, eye gaze)". The wiki entry has some interesting references:      Errol R., Hoffmann (1991) "A comparison of hand and foot movement   times". Ergonomics, Vol. 34, No. 4, pp. 397-406 >A comparison of hand   and foot movement times. (foot vs hand results are clearly presented)      So, R. H. Y. and Griffin, M. J. (2000) "Effects of target movement   direction cue on head-tracking performance". Ergonomics, Vol. 43, No.   3, pp. 360–376. >Effects of a target movement direction cue on hea...   [Ergonomics. 2000] (head moves aren't used to move a cursor)      So, R. H. Y. and Cheung, K. M., (2002) "Combined and interacting   effects of hand and head movement lags on discrete manual performance   in a virtual environment." Ergonomics, 45, 2002, pp. 105–123. >      (head moves aren't used to move a cursor)      So, R. H. Y., Cheung, K. M. and Goonetilleke, R. S. (1999)   "Target-directed head movements in a head-coupled virtual environment:   predicting the effects of lags using Fitts' law". Human Factors, Vol.   41, No. 3, 1999, pp. 474–486. > Target-directed head movements in a   head-coupled... [Hum Factors. 1999] (head moves are used to move a   cursor but a lag is introduced and there is no direct comparison with   hands. Also I don't have access to the full article.)      I skimmed through them but it seems like none of them address the   performances of a head tracking device to move the mouse cursor.   Furthermore they are pretty old and I don't know to what extent those   results can be extended for hands-free mouse performances. Lastly for   whatever reason most of them seem to focus on lag / delay. Are there   any recent results on the performances of head tracking devices used   to move the mouse cursor in comparison with traditional mice?      The best I have found so far is Ashdown, Mark, Kenji Oka, and Yoichi   Sato. "Combining head tracking and mouse input for a GUI on multiple   monitors." CHI'05 extended abstracts on Human factors in computing   systems. ACM, 2005. Combining head tracking and mouse input for a GUI   on multiple monitors, but results seem preliminary, don't use Fitts's   law, and anyway just use head tracking to switch between different   monitors.      I'm also interested in eye tracking as a mouse and foot mice   performances (Errol R., Hoffmann (1991) gives hints for the latter).   Ideally I would like to have table comparing all these ways to control   the mouse ( hand / head / foot / eye).


A difficult integral: $\int_0^{\pi/2} (\log \sin x)^2 \ dx $

$$ \int_{0}^{\frac{\pi}{2}} (\log \sin x)^2 \, dx = \int_{0}^{\frac{\pi}{2}} (\log \cos x)^2 \, dx = \frac{\pi}{2}\left\{ \frac{\pi^2}{12} + (\log 2)^2 \right\} $$ I tried integration by parts, but I ended up with $$ \int_{0}^{\frac{\pi}{2}} (\log \sin x)(\log \cos x) \, dx. $$ I tried to use exponential form for integration but I couldn't integrate further.   Original image:


Suppose $E = \mathbb{Q}(\alpha_1,\alpha_2,...,\alpha_n)$ where $\alpha_i^2\in \mathbb{Q}$ for $i=1,2,...,n.$ Prove that $2^{1/3} \not\in E$.  I thought I could prove it by contradiction but I have made no progress. Can someone share some insights? Thanks a lot!


Package {embrac} seems not to work with math mode in TexLive 2020 on Windows

This MWE \documentclass{article}  \usepackage{embrac}  \begin{document} \textit{some $f(x)$ function} \end{document}  gives me the output below on my two local PCs even after I reinstalled TexLive2020/TexStudio from the scratch on them (Windows 10 user). As we can see it prints some em distances instead of brackets while the package is supposed to print brackets in non-italics inside \textit{} and similar environments.  While same code seems working fine in overleaf.com documents:  I know it is a bit weird to ask people online about what's wrong with my local PCs but maybe somebody knows/can advice/can guess something or check MWE on their windows texlive installations. So what might be wrong there with math mode and package embrac on my installation ? iircembrac shouldn't even touch math mode which makes this issue even weirder. Edit adressing @campa comment: with \listfiles enabled log file shows this:  *File List*  article.cls    2019/12/20 v1.4l Standard LaTeX document class   size10.clo    2019/12/20 v1.4l Standard LaTeX file (size option)   embrac.sty    2019/12/31 v0.9 Upright Brackets in Emphasized Text    expl3.sty    2020-08-07 L3 programming layer (loader)  l3backend-pdfmode.def    2020-08-07 L3 backend support: PDF mode   xparse.sty    2020-05-15 L3 Experimental document command parser xparse-generic.tex l3keys2e.sty    2020-05-15 LaTeX2e option processing using LaTeX3 keys  ***********


Solve the Sturm-Louiville boundary value Problem $u_t(x,t)=u_{xx}(x,t)-bu(x,t)+q(t)$, where $b$ is a constant. Boundary conditions are $u(x,0)=0$ and $u(0,t)=0=u(\pi,t)$, with $0<x<\pi$ and $t>0$.  Following the only example in the textbook, I get:  Assume $u(x,t)$ is of the form $u(x,t)=\sum\limits_{n=1}^\infty B_ne^{-n^2t}\sin(nx)$. But that's for a heat equation: $u_t(x,t)=ku_{xx}(x,t)+q(t)$, boundary conditions $u(x,0)=f(x)$, $u(0,t)=0=u(\pi,t)$.  I don't know what I'm doing and the book and professor are incomprehensible. I really need help.


Philippine passport w/ U.S. Permanent Resident Card (GreenCard) - need Visa to travel to Canada?

Thinking of going on cruise with stops in Canada. I have Philippine passport w/ U.S. Permanent Resident Card (GreenCard). Do i need to get a canadian Visa?  Info on Canada website is a little confusing.


How to do single list to nested list using python

I am newer to python. how do i form the single list to nested list using python. Any one please help me.  content = ['a', 29, 'male', 'cs', 'cs', 'b', 29, 'male', 'cs','cs']   into:  content = [['a', 29, 'male', 'cs', 'cs'],             ['b', 29, 'male', 'cs', 'cs']]


Is there a way to know which route Flixbus will follow to go from A to B?

So the question is pretty straightforward. Is there a way to know which is the route followed by a Flixbus bus from city A to city B, before buying the ticket?


Batch Script for Concatenate multiple raw/binary files - Windows command line < reads from a filtered file and pass it to another cmd

I have different types of file in the same folder, which I have filtered and redirected to a list.txt file, using a separate script.  List.txt has the name of the binary files , which I need to combine together into one binary file.  >type list.txt a.raw b.raw c.raw   Concatenate all the files present in the list.txt to a final.raw file.  >type < list.txt > final.raw  The syntax of the command is incorrect.   Please let me know if there is any option to achieve this on windows cmdline or through some script file.   Note : manually both type and copy cmd is working properly for concatenation. need a script or cmd to do the same.


Blender 2.9 - script how to add a material shader nodes tree?

In blender 2.9, I got a selected object and need to add a new material in a new slot with a script addon. I need some examples for doing a material shader nodes tree in 2.9 Ex: How to adding some nodes like diffuse - glossy mix shader, doing the links setting parameters etc.. may there are some web link to help with that  for 2.9?


Where extra stored energy of Capacitor go ?

Suppose We have a capacitor with capacitance $\ C $  and charge $\ Q $ . So total stored energy is $$ E=\frac{Q^2}{2C} $$ Now if I connect a capacitor with same capacitance parallel with it then current will flow until voltage across both capacitor  become same and this case charges among them will be same . So each capacitor will contain $\ Q/2 $ charges. So energy stored in each capacitor will be $$ E'=\frac{Q^2}{8C}$$ . So total energy in 2 capacitor is $$E_{tot}=\frac{Q^2}{4C}$$ which is not clearly equals to $\ E$ . Where does the remaining stored energy goes ?? When does the loss occur ?


Is there any counterexample to show that $X,Y$ are two random variables and $E(X\mid Y)=E(X)$, but $X$ and $Y$ are not independent.   I already know that if $X,Y$ are independent, then $E(X\mid Y)=E(X)$.


I am looking for an example such that in a pre-Hilbert space $H$ we have for a subspace $U$ that  (i) $\bar{U} \oplus U^\perp \neq H$  (ii) $ \bar{U} \neq U^{\perp \perp}$  Since finite and closed subspaces will probably not do it, I am not good at inventing nice examples. Does anybody here have a few at hand?


Custom keyboard shortcut to lauch a terminal and run a command without exit in the end

I want to create a shortcut to run a command with keyboard shortcut But when I press "alt+ctrl+a" terminal open and immediately close.  Please help me to edit below command for prevent from close after ran it.  gnome-terminal  -e "vnstat -ru -i wlan0 -h"


Etiquette for awarding bounty if none of the answers address the question completely but found to be equally useful

This may be a too-localized question but I still request an answer.    I offered a bounty on the question  worth 100 points. There are three points in the question which needs to be answered. In my bounty note, I explicitly mentioned that "Point 1 and 2 specifically needs to be addressed in detail.".  So far, I've received two good answers, one dealing with point 3 in detail and the other with point 2 and partially with point 1. None of the answers covers all the three points at a time.  My question is, do we have or what should be the etiquette for awarding bounty in cases where all the answers addresses the question equally or not completely?  I already upvoted both the answers;  and   is already .  I'm confused, that's why I asked the question here.


Writing a function with variable number of input arguments

I have a javascript function whose number of input arguments is not known ( has variable number of arguments) and it has also an input dictionary argument called "kwargs" argument which can have some other arguments as (key,value) , like this: function plot( data, kwargs={}){ }  I want to get both the "name" and "value" of the arguments in the body of the function when I call the function with a number of arguments. Suppose that I want to have a function call like this: plot(lines, xlabel="Project",          ylabel="Investor",          xfmt="%", xscale=100, yfmt="%.", yscale=100)  I want to gain "xlable", "Project", "ylabel", "Investor", "xfmt","%" and so on(maybe more arguments) in the function definition. How can I write 'plot' function def?


I just got myself a MBA and I am wondering how do I install Xcode 6 on my MBA?  In the Mac App Store I can see Xcode 5.1.1 so I have started installing that on the MBA. But, I want to install Xcode 6 and more specifically Swift. How do I do that?


Getting Python console in QGIS to do tab completion of file system?

I am trying to have the Python 3 console tab of QGIS 3 complete my file system.   I've tried import sys but this does not allow me to do it.


Help me proving this please. Let $(V,\langle,\rangle)$ be a finite dimensional vector space. Let $T$ be a linear operator on V. Show that $\operatorname{Im}T=(\ker T^*)^\perp$


What is the difference between 'regular' linear regression and deep learning linear regression?

I want to know the difference between linear regression in a regular machine learning analysis and linear regression in "deep learning" setting. What algorithms are used for linear regression in deep learning setting.


When I try to move a model everything in a circle around it moves as well. I was not having this problem and now I am.


Unable to boot after installing systemd-services and changing the init parameter on boot

I tried two different methods but could not install systemd  1st method from , 2nd method from   Confirmation that systemd is not installed:  edward@computer:~$ file /lib/systemd/systemd /lib/systemd/systemd: ERROR: cannot open `/lib/systemd/systemd' (No such file or directory)   Another confirmation:    I'm following the methods proposed in  (against this question was closed as duplicated to), yet for some reason my system doesn't boot.


Getting birth certificate of German born in Romania in 1895

My grandfather was a German born in Romania in 1895. I need to get a copy of his birth certificate to prove he was German, as I need to prove he was German to apply for a German passport for my elderly mom.   How do I go about getting it or proof of his German heritage?


Let $p >3 $ be a prime number and $\Bbb F_p$ denote the ﬁnite ﬁeld of order $p$. Prove that the polynomial $X^2 +X +1$ is reducible in $\Bbb F_p[X]$ if and only if $p ≡ 1\pmod 3.$   Attempt: $X^2 +X +1=\dfrac{X^3-1}{X-1}.$ Now if $x^3=1$ for some $x\in \Bbb F_p$;  $x\in \Bbb F_p^*\implies x^{p-1}=1\implies 3\mid p-1\implies p\equiv 1(\mod 3)$.  How to do the converse?


Does the old Howling Mine have an erratum?

There appears to be two sets of card text on Howling Mine, depending on when it was printed. Do they function exactly the same? Or does the old one not matter if it is tapped or not.


Can anyone provide a simple, inuitive explanation for Noether's Theorem?

I recently came across this theorem for the first time.  As I understand it, what she showed was that conservation 'laws' are often simply an artifact of symmetry or invariance.    For example, the source I read said that conservation of momentum flows naturally if all the physics gives the same answer at all places - e.g., Newton's laws are the same here as they are there.  It also said that conservation of energy derives from the laws of physics being invariant over time.  I sort of see the math in the proof, but don't quite get the intuition.  Can anyone provide a brief explanation?


How has quark electric charge been directly measured?

How has quark electric charge been directly measured when quarks are never directly observed in isolation (due to a phenomenon known as )?


Syntax highlighting and non-ASCII characters

I think Markdown google-code-prettify has some incorrect lexical rules for Java (and possibly other languages).  It correctly identifies this code block from  as being written in Java:  Gl.glLoadIdentity(); float tamaño = texto.Tamaño; double tan = texto.Orientacion.Y / texto.Orientacion.X;   but as you can see, the syntax highlighting of one of the identifiers is messed up.  I am guessing that it does not consider the non-ASCII character 'ñ' to be part of an identifier, whereas Java itself does consider it to be part of the identifier.


Error in loading .mp3 file names in app, showing error I can't find

I am trying to load names of .mp3 files present in download and music directory with void function, it is showing ("getExternalStoragePublicDirectory" is deprecated): private void fillMusicList() {     musicFileList.clear();     addMusicFilesFrom(String.valueOf(Environment.getExternalStoragePublicDirectory             (Environment.DIRECTORY_MUSIC)));     addMusicFilesFrom(String.valueOf(Environment.getExternalStoragePublicDirectory             (Environment.DIRECTORY_DOWNLOADS))); }  Error in LogCat: 2020-06-20 17:57:21.220 8383-8383/? E/m.example.muzi: Unknown bits set in runtime_flags: 0x8000 2020-06-20 17:57:22.084 8383-8383/? E/AndroidRuntime: FATAL EXCEPTION: main  Process: com.example.muzik, PID: 8383  java.lang.RuntimeException: Unable to resume activity  {com.example.muzik/com.example.muzik.MainActivity}: java.lang.NullPointerException: Attempt to get  length of null array     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4205)     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4237)     at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52)     at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)     at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)     at android.os.Handler.dispatchMessage(Handler.java:107)     at android.os.Looper.loop(Looper.java:214)     at android.app.ActivityThread.main(ActivityThread.java:7356)     at java.lang.reflect.Method.invoke(Native Method)     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)  Caused by: java.lang.NullPointerException: Attempt to get length of null array     at com.example.muzik.MainActivity.addMusicFilesFrom(MainActivity.java:77)     at com.example.muzik.MainActivity.fillMusicList(MainActivity.java:89)     at com.example.muzik.MainActivity.onResume(MainActivity.java:109)     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1446)     at android.app.Activity.performResume(Activity.java:7939)     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4195)     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4237)      at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52)      at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)      at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)      at android.os.Handler.dispatchMessage(Handler.java:107)      at android.os.Looper.loop(Looper.java:214)      at android.app.ActivityThread.main(ActivityThread.java:7356)      at java.lang.reflect.Method.invoke(Native Method)      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)


What does circle symbol between two functions means?

I have two function $f$ and $r$, such that: $y = f(x)$, $r(y) = x$. I read that it means that: $f \circ r = I_{U}$, where $x \in U, y \in U$, where $U$ is a finite set. What does $f \circ r = I_{U}$ mean? What does this circle mean and how could i read all this writing $f \circ r = I_{U}$ ?


Describe $\mathbb{R}[x]/(x^{2}+ax+b)$ where $a,b \in \mathbb{R}$

So obviously using quadractic formula, we have three cases for the roots which depends on the discriminant. I am not sure if I am right on this but,  Case 1: $a^{2}-4b>0$.   Then we have two distinct real roots so this factors as $$\mathbb{R}[x]/(x-\alpha) \oplus \mathbb{R}[x]/(x-\beta).$$ (My guess here is since $\alpha$ and $\beta$ are different, these two ideals are comaximal so I can apply the Chinese Remainder Theorem). But this is isomorphic to $$\mathbb{R} \oplus \mathbb{R}.$$  Case 2: $a^{2}-4b < 0$.  In this case, we have a complex root so we have an extension of degree $2$. But obviously whatever root we have, this is contained in $\mathbb{R}[i]\cong \mathbb{C}$ so we must have this is $\mathbb{C}$ by the tower law since $\mathbb{R}[i]$ is also a degree $2$ extension of $\mathbb{R}$.  Case 3: $a^{2}-4b=0$.  Then we have a real root with multiplicity $2$. I am not sure what this is as if we have the root is $\alpha$, we get $$\mathbb{R}[x]/(x-\alpha)^{2}$$ Since these roots are the same, $(x-\alpha)$ and $(x-\alpha)$ are not comaximal I believe so I don't know what this ring is.


Motivating sigmoid output units in neural networks starting with unnormalized log probabilities linear in $z=w^Th+b$ and $\phi(z)$

Background: I'm studying chapter 6 of Deep Learning by Ian Goodfellow and Yoshua Bengio and Aaron Courville. In section 6.2.2.2 (pages 182 of 183 ) the use of sigmoid to output $P(y=1|x)$ is motivated.  To summarize some of the material they let $$z = w^Th+b$$ be an output neuron before an activation is applied where $h$ is the output of the previous hidden layer, $w$ is a vector of weights and $b$ is a scalar bias. The input vector is denoted $x$ (which $h$ is a function of) and the output value is denoted $y=\phi(z)$ where $\phi$ is the sigmoid function. The book wishes to deﬁne a probability distribution over $y$ using the value $z$. From the second paragraph of page 183:     We omit the dependence on $x$ for the moment to discuss how to deﬁne a   probability distribution over $y$ using the value $z$. The sigmoid can be motivated by constructing an unnormalized probability distribution $\tilde P(y)$, which does not sum to 1. We can then divide by an appropriate constant to obtain a valid probability distribution. If we begin with the assumption that the unnormalized log probabilities are linear in $y$ and $z$, we can exponentiate to obtain the unnormalized probabilities. We then normalize to see that this yields a Bernoulli distribution controlled by a sigmoidal transformation of z:   \begin{align} \log\tilde P(y) &= yz \\ \tilde P(y) &= \exp(yz) \\ P(y) &= \frac{\exp(yz)}{\sum_{y'=0}^1 \exp(y'z) } \\ P(y) &= \phi((2y-1)z) \end{align}   Questions: I'm confused about two things, particularly the first:   Where is the initial assumption coming from? Why is the unnormalized log probability linear in $y$ and $z$? Can someone give me some inituition on how the authors started with $\log\tilde P(y) = yz$? How does the last line follow?


When to give more information than what is asked in question?

Something that got me wondering.  I have answered a couple of questions on the sites.  At times giving more information to the question than what was asked for.  This is also information that is readily available if you use some hardy Google skills.  This has led to a couple of comments where, users has stated that "This is not what was asked" or "To much information".  What if the more information enables the OP to make a better decision regarding the question that he had or shows the OP another way of doing something.  Do one give more information or do you stick to the problem at hand?


, it'll "Open with" How could i get the file that was "opened with" my python script. Currently i type the name of the file : zipname = input("Enter .osz file : ") with zf.ZipFile(zipname+".osz","r") as zip:  But i wanted to know if i can speed up the process like this. I already searched the question but i haven't found anything.


How does a rocket obey Newton's third law?

How does a rocket push against its exhaust? Does the reaction come from the rocket nozzle or as a result of the imbalance of forces in the combustion chamber?


Is the distributive law of multiplication valid when the number of terms are variable?

In brief the distributive law for natural numbers states that: Let $a$,$b$,$c$ naturals then $a \cdot (b+c) = a\cdot b + a\cdot c$ And this could be generalized by induction: Let $a, a_1, a_2, \ldots a_n$ naturals then $a\cdot (a_1 + a_2 + \ldots +a_n) = a \cdot a_1 + a\cdot a_2 + \ldots +a\cdot a_n$ Those are valid propierties  with other objects, for example, integers, real numbers, complex numbers, matrices, functions, etc.  because their definition is based on this. But what happens when $n$ is not a fixed natural but a variable? I'm interested in this because I want to know if the following is valid: Let $N$ be a natural number, then: $$ N = \overbrace{1+1+\ldots +1}^{N- times}$$ and multiplying by N on the left in both sides of the equality we get $$ N\cdot N = N \cdot(\overbrace{1+1+\ldots +1}^{N- times}) $$ now the left hand side becomes $N^2$ and until this point I agree this is valid. But I'm not sure that $N \cdot(\overbrace{1+1+\ldots +1}^{N- times}) = \overbrace{N + N + \ldots + N}^{N- times}$ becasue this will bring a contradiction if we think this as a function. $$N^2 = \overbrace{N + N + \ldots + N}^{N- times}$$ and derive both side with respect to N $$ \frac{d}{dN}(N^2) = \frac{d}{dN}\left((\overbrace{N + N + \ldots + N}^{N- times})\right) \\ 2N = \overbrace{1 + 1 + \ldots + 1}^{N-times} = N$$ And clearly the function $N$ is not equal to the function $2N$, hence a contradiction I'm sure that the distributive law is failing with the derivative operator, but I'm not sure with the multiplication operator. Being more specific: if $c$ is a constant and $v$ a variable is the following assertion valid? $$\overbrace{ c + c +c \ldots +c }^{v -\text{times}} =^{?} c \cdot(\overbrace{1+1+\cdot+1}^{ v-\text{times}}) $$ EDIT Because some users identified this as a possible duplicate of: . I want to add more information to explain why that does not answer my question. My current question is not about the derivative or why the proof fails, that is well answered there. My query is, as stated in the title, about the validity of distributive law when the amount of terms are variables.  Another example: Let  $n$ be a constant  thus $$ \sum_{k=0}^{n} 2^k = 2^0+2^1+...+2^n$$ (the upper n-times brace is obviated here) but if $n$ is a variable we could tend to infinity but this may cause trouble when trying to apply the basic arithmetic law: $$\sum_{k=0}^{\infty} 2^k = 2^0+2^1+2^2+... \\  = 1 + 2 \cdot (2^0 + 2^1 + 2^2+ \ldots ) \text{(Distributive law when $n$ variable tend to infinity)} \\ = 1 + 2 \cdot \sum_{k=1}^{n} 2^k   $$ But this is absurd because if the identity holds then: $$\sum_{k=0}^{\infty} 2^k = -1$$ The sum of only positive numbers being a negative number. So we cannot apply freely the basic properties of numbers when they are variable because that variable may behave like infinity. EDIT 2 Well, I will be the most specific I could reach here and if this doesn't have an answer I give up. Let $a$ be a number and $\{a_j\}_{ j\in J}$  an indexed collection of numbers. Then $$ a \cdot \sum_{j\in J}a_j = \sum_{j\in J}a\cdot a_j$$ if $J$ is finite. That's for sure, we begin with the (I think axiom) distributive law for naturals. But what if J is not finite. ie. be infinity but numerable or infinity but not numerable. This property still holds?  If so why? because the generalization of induction uses a set not finite but numerable. So it may not work when the set of index is not finite and not numerable.


Why XML-Serializable class need a parameterless constructor

I'm writing code to do Xml serialization. With below function.  public static string SerializeToXml(object obj) {     XmlSerializer serializer = new XmlSerializer(obj.GetType());     using (StringWriter writer = new StringWriter())     {         serializer.Serialize(writer, obj);         return writer.ToString();     } }   If the argument is a instance of class without parameterless constructor, it will throw a exception.     Unhandled Exception:   System.InvalidOperationException:   CSharpConsole.Foo cannot be serialized   because it does not have a   parameterless constructor.    at   System.Xml.Serialization.TypeDesc.CheckSupported()   at   System.Xml.Serialization.TypeScope.GetTypeDesc(Type   type, MemberInfo sourc e, Boolean   directReference, Boolean throwOnError)   at   System.Xml.Serialization.ModelScope.GetTypeModel(Type   type, Boolean direct Reference)    at   System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping(Type   type , XmlRootAttribute root, String   defaultNamespace)    at   System.Xml.Serialization.XmlSerializer..ctor(Type   type, String defaultName space)    at   System.Xml.Serialization.XmlSerializer..ctor(Type   type)   Why must there be a parameterless constructor in order to allow xml serialization to succeed?  EDIT: thanks for cfeduke's answer. The parameterless constructor can be private or internal.


Are there distributions where no conjugate prior exists? Is there a necessary and/or sufficient condition which guarantees the existence of a conjugate prior? Edit: Why has this question been closed? None of the two questions which are supposed to answer this question actually answers this.


How to create a installation Ubuntu flash drive

I have a smal laptop Acer aspire and I wish to install ubuntu from a flash drive how do I proceed?


what is the difference between “make of” and “make from”?

I want to ask a thing make from/of something but I don't know how.  What are they make from? What are they make of? what do they make from? what do they make of?


For $0 \to N' \to N \to M \to 0 $ with $N$ finitely generated and $M$ finitely presented then $N^{'}$ is also finitely generated.

Let $M$ be a finitely presented $R$ module and $0 \to N' \to N \to M \to 0 $ be an exact sequence with $N$ a finitely generated $R$ module. Prove that $N'$ is also a finitely generated $R$ module.  By $M$ finitely presented $R$ module we mean there is a ses $0 \to K \to F \to M \to 0$ where $F$ is free of finite rank and $K$ is finitely generated $R$ module. I proved the case when $N$ is free of finite rank but can't show it in this case. Any help will be appreciated. Thanks.


Arrangement of integers in a row such that the sum of every two adjacent numbers is a perfect square.

Inspired by this  and in order to solve an old problem, I have the following question:      Can we construct a strictly increasing sequence $(N_i)_{i\in \mathbb{N}}$, such that for every integer $i$, we can arrange all the numbers from 1 to $N_i$, in a row such that the sum of every two adjacent numbers is a perfect square.   The first term of the sequence cannot be less than $14$, so we can take  $N_0=15$: $$8,1,15,10,6,3,13,12,4,5,11,14,2,7,9$$ And we can take also $N_1=16$ because we can add $16$ at the end, and $N_2=17$ by adding $17$ in the beginning (@mathlove). And as pointed by @gnasher729  in his answer we can not take $N_3=18$.  This is related to the connectedness  of a graph, if we consider the graph $G_N = (V, E)$ with $V=\{1,\cdots,N\}$ and $\{i,j\}\in E$ if and only if $i+j$ is a square, The question is equivalent to prove that $G_N$ have a Hamiltonian path for large integers $N$.  Edit I updated the question, I hope it's very clear and more direct.


jQuery how to bind onclick event to dynamically added HTML element

I want to bind an onclick event to an element I insert dynamically with jQuery  But It never runs the binded function. I'd be happy if you can point out why this example is not working and how I can get it to run properly:    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"                     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">                             <title>test of click binding</title>
Test of click binding

problem: to bind a click event to an element I append via JQuery.

The link is created, then added here below:

Another is added here below:

                         EDIT: I edited the example to contain two elements the method is inserted to. In that case, the alert() call is never executed. (thanks to @Daff for pointing that out in a comment)


Indent at paragraph following an equation and a figure

In one section of my document I have several equations. Due to the normal separation of paragraphs trough the equations I do not have any further passages in the text. Somewhere in the middle of the section I want to include a figure. As the section is quite long I don't want to set the \begin{figure} ... \end{figure} at the end of the section as the graphic would not be in the right position.  But if I am entering the graphic as shown in the example I get an indent at the beginning of the next paragraph after the equation.  Is there any way to prevent this?  \documentclass[parskip=full]{scrbook} \usepackage{lipsum} \usepackage{graphicx} \begin{document} \lipsum[1] % \begin{equation} 1+2=3 \end{equation} % \begin{figure} \centering \includegraphics[width=0.4\linewidth]{example-image-a} \end{figure} % \lipsum[2] \end{document}     Solution:  Commenting the line \end{figure}% prevents the extra space at the beginning of the new paragraph.


Found a similar question , but with some minor differences. Is it archaic to use have you in sentences such as this:     John : I think we can see it with a specially crafted telescope.   Mary : Have you such a telescope?   instead of     Mary : Do you have such a telescope?   Is it still used in official and casual conversations?


Water is pouring into a conical tank at a rate of 8 cubic feet per minute.  If the height of the tank is 12ft, and the radius of its circular opening is 6ft, how fast is the water level rising when the water is 4ft deep?   This is an in-class example that my professor used. The work below is how he solved the problem.     Volume of water is $V=V(t)$ Depth of water is $h=h(t)$  The relationship between V and h is:  $$V=\frac 13 \pi r^2h$$  $r=\frac rh$, and $\frac rh=\frac 6{12}=\frac 12$  So, $V=\frac13\pi(\frac h2)^2h=\pi h^3$       How did he get the $\frac h2$?    $\frac {dv}{dt}=\frac {\pi}{12}3h^2(\frac {dh}{dt})= \frac {\pi}4h^2(\frac {dh}{dt})$  When $h=4$, $\frac {dv}{dt}=8$.  $8=\frac {\pi}4(4)^2(\frac {dh}{dt})$  $\frac {dh}{dt}=\frac {\pi}2$      Let's see if I understand this. I've tried a similar problem with different values.  Water is pouring into a conical tank at a rate of 8 cubic feet per minute.  If the height of the tank is 10ft, and the radius of its circular opening is 5ft, how fast is the water level rising when the water is 4ft deep?  Volume of water is $V=V(t)$ Depth of water is $h=h(t)$  The relationship between $V$ and $h$ is$$V=\frac 13\pi r^2 h$$  $h_0=$ the height of the cylinder $=10ft$, $r_0=$ the radius of the opening $=5ft$  $$\frac rh=\frac {r_0}{h_0}=\frac 5{10}=\frac 12$$  $$r=h(\frac 12)=\frac h2$$  so, $$V=\frac 13 \pi (\frac h2)^2h=\frac {\pi}{12}h^3$$  When $h=4ft$ and $\frac {dV}{dt}=8ft^3/min$,  $$\frac {dV}{dt}=\frac {\pi}{12}h^3(\frac {dh}{dt})$$  =$$8ft^3/min=\frac {\pi}{12}(4)^3(\frac {dh}{dt})$$  = $$8=\frac {\pi}{12}(64)(\frac {dh}{dt})$$  = $$\frac {dh}{dt}=\frac 8{\frac {64\pi}{12}}=\frac {96}{64\pi}$$  =$$\frac {dh}{dt}=\frac 3{2\pi}ft^3/min$$


How can I change My monitor Imageing postion to left when i set low resolution?

ITs not a multiple-monitor related question. I have a 3440 * 1440 monitor. Accidently the right side of the panel is broken. So I was trying to project the screen to the left side in 2550 * 1440 resolution. But when scale it as aspect ratio and change the resolution, the projection remains in the center  I was trying to move it to the left side of the monitor to make the monitor usable for a couple of days.


so I attemted to solve the following: planet X of mass $8.8 \times 10^{27}$ kg has a moon of an unknown mass which orbits every 17 days from a distance of approximately one million km ( center to center). What is the approximate mass of moon?  Given: $M = 8.8 \times 10^{27}$kg  m = ?  f (frequency)= 17  $d= r= 10^6$km= $10^9 m$  mechanical system chosen the moon. from newtons 2nd law (sigma) $F = m\times a$ $F(g) = m\times a(c)$ here I assume that the only force applying on the moon is gravity of the planet X, an it has a circular acceleration so I got: $G\times M\times m/r^2 = m\times 4π^2 \times  d \times f^2$  However, the $ m$, mass of moon cancels out, and I'm supposed to find it.  so?


Changing inner nested list changes whole list


Shell's process group ID = foreground job's process group ID?

I decisively conclude that Shell's process group ID = foreground job process group ID from the 2 sources below. When a background job is selected to run in the foreground, is it the shell's process group ID that changes to the foreground job's process group ID or the reverse?  1.     To facilitate the implementation of the user interface to job control, the operating system maintains the notion of a current terminal process group ID. Members of this process group (processes whose process group ID is equal to the current terminal process group ID) receive keyboard-generated signals such as SIGINT. These processes are said to be in the foreground. Background processes are those whose process group ID differs from the terminal’s; such processes are immune to keyboard-generated signals.    2.        Addition:  $sleep 3000 & $sleep 2000 & $ps xao pid,ppid,pgid,sid,tty,comm | grep tty  PID     PPID    PGID    SID     TTY     COMMAND 1153    1135    1153    1153    tty1    bash 1173    1153    1173    1153    tty1    sleep 1189    1153    1189    1153    tty1    sleep 1219    1153    1219    1153    tty1    ps 1220    1153    1219    1153    tty1    grep


Can I clear an area of my prison for everyone BUT max security prisoners?

How can I make sure that only low and medium security inmates are in a specific area? Is it possible to reverse the overlay you can set? It seems like you are only able to clear areas for low OR medium security prisoners, but sharing is not possible. The thing I want here is to make sure that max security prisoners are not in certain areas.


I want to copy all files *.pdf to *_0.pdf  How can I do it?


As I remembered, at the 2 poles of a battery, positive or negative electric charges are gathered. So there'll be electric field existing inside the battery. This filed is neutralized by the chemical power of the battery so the electric charges will stay at the poles.  Since there are electric charges at both poles, there must also be electric fields outside the battery. What happens when we connect a metal wire between the 2 poles of a battery? I vaguely remembered that the wire has the ability to constrain and reshape the electric field and keep it within the wire, maybe like an electric field tube. But is that true?


Identify that text exceeds parbox height

I'm trying to identify through warnings when a text exceeds it's container parbox height with no luck.  Here is my code.  \documentclass{article} \usepackage[english]{babel} \usepackage{blindtext} \usepackage{xcolor}  \begin{document}     \fboxsep0pt      \newlength\myhg     \newsavebox{\testparbox}     \savebox{\testparbox}{\colorbox{red}{\parbox[b][50pt][t]{0.50\textwidth}{\blindtext}}}     \settoheight\myhg{\usebox{\testparbox}}     \usebox{\testparbox}     \the\myhg \end{document}   This generates the following pdf.    Even though the text exceeds the parbox by a considerable amount of space there are no warnings in the log outputs.   How can I identify this and throw a warning when it happens?


Which Lubuntu website is the correct one?

There are two totally different websites offering Lubuntu:      What is their difference?


Apex web service works in Workbench, but tests fail

I'm trying to complete the , but am having some difficulties.  The code I've written appears to function correctly when I access it via Workbench, but I can't persuade my unit tests to pass.  My SUT class is like this:  @RestResource(urlMapping='/Accounts/*/contacts') global class AccountManager {     @HttpGet     global static Account getAccount()     {         RestRequest req = RestContext.request;          String accId = req.requestURI.substringBetween('Accounts/', '/contacts');          system.debug(accId);          return getAccountById(accId);     }      public static Account getAccountById(string account_id)     {         Account acc = [SELECT Id, Name, (SELECT Id, Name FROM Contacts)                         FROM Account WHERE Id = :account_id];          return acc;     } }   When I call this via Workbench, the response looks sane:    My test looks like this:  @isTest static void TestGetAccountById() {     RestRequest request = new RestRequest();     request.requestUri = 'https://playful-raccoon-288300-dev-ed.my.salesforce.com/services/apexrest/Accounts/0011r00001nUpkgAAC/contacts';     request.httpMethod = 'GET';     RestContext.request = request;     // Call the method to test     Account thisAcc = AccountManager.getAccount();      system.debug('here');     // Verify results     System.assert(thisAcc != null);     System.assertEquals('Bluebeards Grog House', thisAcc.Name); }   The exception I'm getting is:     System.QueryException: List has no rows for assignment to SObject   I understand from my research that this means that the query is returning 0 rows. This confuses me because the account ID being passed is the same as the one I'm using in Workbench. I wondered if my logic for extracting the account ID was wonky, but I've been able to verify this using checkpoints.  Am I missing something very obvious?


No such file or directory but I can see it!

I'm trying to run a python script, on a headless Raspberry PI using winSCP and get the following error message:  Command '"./areadetect_movie_21.py"' failed with return code 127 and error message /usr/bin/env: python : No such file or directory.   When I try and run from terminal, I get:  : No such file or directory.   I try a similar python script, in the same directory, with the same python shebang, the same permissions and using the same user pi, and it works.  I also do a ls and I can see the file, so I don't know why it will not run.


How do I determine how much RAM I actually need?

Due to space constraints, I need to purchase a laptop to replace my desktop computer. However I don't know whether I need a laptop with 8GB or 16GB of RAM. My desktop currently has 16GB.  What is the easiest way to run something in the background to determine my typical RAM usage over a period of, say, a month? My goal is to have enough data to base my RAM purchase on real-world usage of my desktop.  I've seen a few articles describing how to use Performance Monitor to do this, but they all seem to suggest different things to monitor. Several of them also talk about measuring my swap, which I don't believe I should be interested in.


Cannot register on commandlinefu with Stack Exchange OpenID

Cannot Complete Login      Detected an attempt to send an assertion when the identifier () is not owned by the logged in user.      If you believe you encountered this message in error, please report it.   Login page:


How do I make an application's user settings persist from one version to the next?

In a Visual C# project's properties, I can go into Assembly Information and change both the assembly version and the file version. I've found that when I change the assembly version, a new folder is created in C:/Users/[username]/AppData to save any changes to user-scoped settings. This means any changes that were made in a previous version are lost and the settings are restored to their defaults. This can especially be a problem if the settings store important information like file paths and the application is shared by multiple users and the new user doesn't know how to change the settings to make it the way it was before the update.  Is there a standard solution to this problem? How do applications normally save a user's settings when the assembly version changes? Do applications normally just not change the assembly version at all unless they want to reset the settings to their defaults? I could just store data in a different file but I want to know if this can be done while still using user.config.  Also, how do I see what an exe's assembly version is? In its properties, the details tab shows "file version" and "product version" but they both reflect the file version that was set in Visual Studio.


In \URL --- \% appears as \% instead of %.  But % itself works as a comment...


Is it possible to use a 32-bit driver on 64-bit Windows 7?

I know it's not possible to install a 32-bit driver in the traditional way, but I really cannot find a 64-bit driver for my memory card reader. Is there anyway I can somehow use this device with a 32-bit driver on a 64-bit Windows 7 installation?  I was thinking there might be a way to run a device in compatibility mode? Possibly even have a 32-bit device layer emulator or something?  I'm interested in any method to get this device up and running.


Slick proof the determinant is an irreducible polynomial

A polynomial $p$ over a field $k$ is called irreducible if $p=fg$ for polynomials $f,g$ implies $f$ or $g$ are constant. One can consider the determinant of an $n\times n$ matrix to be a polynomial in $n^2$ variables. Does anyone know of a slick way to prove this polynomial is irreducible?  It feels like this should follow quite easily from basic properties of the determinant or an induction argument, but I cannot think of a nice proof. One consequence of this fact is that $GL_n$ is the complement of a hypersurface in $M_{n}$. Thanks.


Prove the module of a holomorphic function cannot be $\frac{K}{\cosh x}$

Prove that there does not exist any holomorphic function $f(z)$, such that $|f(z)| =\frac{K}{\cosh x}$ where $K>0$ is a constant, and $x=Re(z)$.   My idea is to use the maximum modulus principle. $|f(z)| =\frac{K}{\cosh x} = \frac{2K}{e^x+e^{-x}} \leq K$. An entire function with bounded modulus must be a constant. This leads to a contradiction.  My question is, in my attempt, I assume $f$ to be holomorphic on $\mathbb{C}$. Is it possible to prove the same result when $f$ is holomorphic on $\Omega$ where $\Omega$ is a domain? And is it possible not to use maximum modulus principle?  Thank you for any help!


How can I verify users the first time they log in?

I was reading  article. I would like to know how logging in with the REST API in Drupal 8 works. By default, when users log in, Drupal will verify username and password. After the login, the browser has a cookie for the created session.        With the REST API, how can Drupal 8 verify users the first time they log in? After the login, how does it check the current login?


What can be used as formal euphemism of "hack"?

I'm writing a technical document, and I need to convey the fact that we had to find a non-optimal, non-orthodox solution that was adopted as the best available alternative (a hack) to solve an otherwise problematic issue.  Please note that I refer to the positive meaning of "hack", and not at the negative one, as clarified in .  To me, "escamotage" doesn't sound really appropriate in a technical document, and "hack" seems a bit informal and not very "technical".  Is there a construction that can help?


I'm trying to change the text in my TextView by using the setText().  When I try to do this I get the following error:  E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{<bla bla bla>}: java.lang.NullPointerException  Caused by: java.lang.NullPointerException             at com.training.mytraining.test.MainActivity.display(MainActivity.java:35)   MainActivity.java  public class MainActivity extends AppCompatActivity { TextView tvCountry; private Server theServer;   @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);      tvCountry = (TextView) findViewById(R.id.countryTextView);       theServer = new Server(this);     theServer.weatherFromYahoo();   }   public void display() {      tvCountry.setText("USA"); }   }   Server.java  public class Server extends AppCompatActivity { MainActivity theMainActivity;  //Constructor public Server (Context context){     this.theMainActivity = new MainActivity(); }  public void weatherFromYahoo() {      theMainActivity.display(); }   }  activity_main.xml  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">  <TextView     android:id="@+id/countryTextView"     android:text="@string/hello_world"     android:layout_width="wrap_content"     android:layout_height="wrap_content" />     This is just an example of my real code. I did'nt want to put all the code, so I made a new code with just that problem I get. I have to set the text by calling my MainActivity from an another class.  Please help me, I have been stuck here for hours.


What is the difference between snaps and Ubuntu Software Center-based apps?

I have my Ubuntu Software Center set up to display available snaps. Some apps have both a snap version and an Ubuntu Software Center version available. However, I don't know what the difference is between them. I've seen rumors that snaps are self-updating, but I don't know if Ubuntu Software Center apps can do that, too. In general, I'm wondering what the differences and pros/cons are between the two.


Is it possible to run networking commands like nmap in WSL?

I recently got the Windows 10 anniversary update and installed bash. I tried installing nmap, but it wouldn't run.  My question: Is there any way for commands like nmap to correctly run in WSL?  Thanks in advance!  Error I get when running sudo nmap -sn 192.168.1.*: route_dst_netlink: cannot bind AF_NETLINK socket: Invalid argument  I remember reading somewhere that WSL doesn't have support for sockets, but can use TCP. Is this possible in this case? Also, will WSL ever have support for sockets?


Ditto has now been released in the latest patch, and I would like to catch one.  What are the conditions to capture a Ditto? Does it show up on the nearby tracker? Or will it transform into something?


Does there exist an answer to the next question: How many groups of order $n$ ($|G|=n$, $n\in \mathbb{N}$) are exist up to isomorphism?  (The groups are not necessarily Abelian) I am curious about this question.  If the answer ($\forall n\in\mathbb{N}$) does not exist,does the answer exist for $n=$? $6$? $10$?  (The question about $n=1,2,3,4$ (and primes or p*q) is easy because the groups are abelian).


A finite field is not algebraically closed.

I was looking at  which explains why finite fields are not algebraically closed. But the comment of Joshua Tilley made me doubt. If $K=\{\alpha_1,\ldots,\alpha_n\}$ is a finite field then the polynomial $p(x)=(x-\alpha_1)\ldots (x-\alpha_n)+1$ is just constant no? But the definition of algebraically closed is that every non-constant polynomial has a root. So how does this prove anything? I know there is something I don't get since it is not the first time I see this proof.


When trying to simplify $\frac{1}{\sqrt{-1}}$, you could rationalize it: $$\frac{1}{\sqrt{-1}}\cdot\frac{\sqrt{-1}}{\sqrt{-1}}=\frac{\sqrt{-1}}{-1}=-\sqrt{-1}$$ Or you could simplify it as one radical: $$\frac{1}{\sqrt{-1}}=\frac{\sqrt{1}}{\sqrt{-1}}=\sqrt{\frac{1}{-1}}=\sqrt{-1}$$ These are obviously different answers. I'm pretty sure the first method is algebraically sound and the second method might not be because of maybe a branch cut. Could someone please explain why the answers are different, and which is correct?


How to include custom non-system folder under This PC in Windows 8.1?

I've recently upgraded from Windows 8 to 8.1 and noticed the restructured This PC folder, formerly Computer.   What I want to achieve is to include custom folder under "This PC".    What I've found after googling is that what is displayed under "This PC" is stored in registries under   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\MyComputer\NameSpace  However those folders (such as Desktop, Documents, etc) are referenced via CLSID and the folder I want to include in the list does not have CLSID.


To which Schengen country should I apply for multiple city travels?

I am traveling to Amsterdam (2 nights), Paris (2 Nights), Rome (3 nights) and Zurich (3 nights). However, I am landing in Brussels and then taking a train on the same day to Amsterdam. To which country should I apply for the visa?


diffirence between "i have no..." and "i've got no..."

Is there a diffirence between 'i have no evidence' and i've got no evidence'?


Why does foam build up when boiling food with the lid closed?

There's a .  When you boil some food like pasta or legumes without the lid, there's almost no foam, but when you put it on, the foam quickly builds up and runs over the edges. When you remove the lid, it disappears almost immediately. Why?


Polynomial irreducible $\implies $ "Reverse" polynomial irreducible

If $$a_nx^n+\cdots +a_0$$ is irreducible over some field, the polynomial $$a_0x^n+\cdots +a_n$$ with the coefficients reversed is irreducible over the same field as well.   Suppose the polynomial can be expressed as product of two polynomial the original polynomial will be reduced. Thats what I want to do but I ran out of idea. can someone help me?


Is there a setting to make the file browser sort by date everytime. I want to see my most recent blend files each time but I always have tell the browser to sort by date


Joomla foreach loop item: How to show just 1 item and stop the loop?

I need to stop the foreach loop which continues will creating items if they are posted. Because my design is small,  I want to show 1 item. The others items, I can show it in a new iframe when they click on the button "Show more", Which I created.  <?php foreach ($this->items as $item) { ?>     <?php if ($item->published == 0) continue;?>       //code   <?php }?>


I have bought a new HP Envy (512 SSD/32 Optane) laptop and dual booted with Ubuntu 19.10 WiFi adaptor not found. I searched a lot and found that issue of iwlwifi driver . its a proprietary driver not working in Ubuntu by default. I tried to download firmware for AC-9560 and modprobe iwlwifi. But no success.  EDIT: Solved using the below code from   sudo apt update sudo apt install git build-essential git clone https://git.kernel.org/pub/scm/linux/kernel/git/iwlwifi/backport-iwlwifi.git cd backport-iwlwifi/ make defconfig-iwlwifi-public sed -i 's/CPTCFG_IWLMVM_VENDOR_CMDS=y/# CPTCFG_IWLMVM_VENDOR_CMDS is not set/' .config make -j4 sudo make install sudo modprobe iwlwifi


My wife uses a Droid (first gen) running v2.2, and in the past month or so she can no longer download or update apps from the Market. We've tried rebooting the phone without any luck. The phone has internal storage available, so I don't believe that's an issue. Please help!


Getting "experimental" true displacement to work

I have been trying to achieve a true mesh displacement on meshes for quite some time, without ever getting it to work.  If I understand it correctly, this experimental feature would allow me to easily displace the vertices of a mesh - or to create new mesh vertexes where needed - to get a displaced mesh in the result, based off an image, but without using a bump map (simpler, faster?).   This all sounds very exciting in theory, but I am having a really hard time finding examples or tutorials that are both recent and whose links function. So I think there is the need for a question here which will call upon detailed and recent answers to bridge that gap.  I'll start with a simple ico sphere:    Then, , I will change the Feature Set to the Experimental one:    I then add a pink granite image to the mesh:    Mark Seams, Unwrap, add image in the UV Editor:      and finally, in the Object Data panel, change the Displacement method from Bump to True as explained :    no result yet:    if I click "Use Subdivision" this is what I get (so I won't click it right now):    Looking into the Node Editor, nothing seems to have changed with the Displacement of the mesh:    so I tried to replicate the node setup seen in  of  (Linear isn't an option, Clip, Single and Repeat are):    ... but the result is a white ICO Sphere, similar to Image 1.  So, can the "Experimental Feature Set" be used to create actual displacement, and modify a mesh?  This is what I'm trying to obtain - but with the image of the texture actually displaying on the mesh (image from ):    .blend file:


Replacing a switch where power comes thru the fan to the timer switch, with only 2-wires?

I can see an answer where it suggests a 3-wire run from the fixture but I'm hoping to use existing wiring and it only has black and white wires coming from the bathroom fan to the old timer switch.   The new modern timer switch has red, white and black wires out (and green of course).  Which wires connect to which wires please?  and thanks Scott


Looking for a short story involving robotic proxy warfare on the moon

War was banished from Earth, and instead operated by proxy on the Moon. Belligerent nations would each send robots (not necessarily androids) to the moon to compete for supremacy in the given conflict.   The short story detailed a "world war" that was something like WW XVII or some other number well beyond II or III. The mechanisms by which they attacked each other were interesting; things like interfering with each others ability to isolate or dissipate waste heat while in vacuum.   I believe I originally read it in an Analog Magazine that would have originally been published in the 1970s or early 1980s.


When you press the windows key, type Chrome, but spell it wrong, IT OPENS EDGE! I had an option configured, that Cortana was completely disabled and I wouldn't get web-results either, after updating to Windows 10 Home 1803 (17134.228), I get the web results again, I've played around in the registry, and the group policy editor, but still, I get these web-results.  I tried this trick I found at , It said to run this registry file:  [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Search] „BingSearchEnabled“=dword:00000000 „AllowSearchToUseLocation“=dword:00000000 „CortanaConsent“=dword:00000000   But as mentioned, this was useless. not even after a restart.


If $n > 2$, show that $$\left(n!\right)^2 > n^n$$  Although the problem is pretty obvious, I couldn't come up with a rigorous proof. I was thinking some sort of AM-GM, but couldn't build anything concrete.  I have a feeling this problem could be a duplicate, I tried to google, and even searched on the stackexchange network, couldn't find it.


If $\sum_{k = 1}^\infty \frac{a_k}{k} < + \infty$, then $\frac{1}{n} \sum_{k = 1}^n a_k \to 0$

I'm currently reading a paper, where they assert that for a nonnegative sequence $a_k$ of real numbers with $\sum_{k = 1}^\infty \frac{a_k}{k} < + \infty$, we have $\lim_{n \to \infty} \frac{1}{n} \sum_{k = 1}^n a_k = 0$.   My attempt to prove this was using the following idea: If $a_k > \varepsilon > 0$ for all $k \geq k_0$, then $$ \sum_{k = 1}^\infty \frac{a_k}{k} > \varepsilon \sum_{k = k_0}^\infty \frac{1}{k} = + \infty.$$   So we should have some decay condition on the $a_k$. However, we could have $a_k$ to be the characteristic function of $\{ n^2 : n \geq 1 \}$ for instance; then we can't compare the series $\sum_{k = 1}^\infty \frac{a_k}{k}$ to the harmonic numbers; but then we can equally deduce the fact since square numbers have density zero.   I know that this is very vague. The reason for this is, that I couldn't get the idea to work.  How can I prove the fact?  Thanks!