I've got this small gray box on the top-left corner that stays above all windows. Right-clicking etc on it does nothing.    You can see it on top of the recycle bin icon in the pic above. What is that? I checked the Users tab on task manager and I was the only user running, I tried closing a bunch of running apps in system tray, etc.

Periodically when I select a menu command, the label or selected option gets "stuck" on screen and won't go away. I can close all open applications, including whichever one I was using when it got stuck, but it still won't go away.   In the screenshot below, I opened an new instance of IE just to show how the label stays on top. The label was not created by this instance of IE.    (I added the circle in MS Paint. That part isn't stuck.)  The label that gets stuck is the first menu command I select in IE. If a label is already stuck, a new one does not get stuck (regardless of which instance(s) of IE are involved). Based on this knowledge, I now just open IE on my secondary monitor, carefully open the context menu so the Properties command is in the bottom corner, and click it. This is not a solution.  The floating label never moves and is transparent to mouse input (if I click it, it's as if I clicked the item behind it).  The label does not go away if I close all running applications. I haven't tried stopping services or closing system tray items like Live Mesh.  The label does go away if I change the screen resolution and then change it back.  Any ideas how I can stop this from happening? It's happened a half dozen times and it's becoming quite disrupting to my work.


So I wanted to make a Blender game and I've been working on the exterior now suddenly after about three days of working on it, Blender will no longer call the textures I need it to and I wind up with this, which is completely undesirable. The textures for some reason show in the materials tab but not in the textures tab nor in the Materials viewing pane. Is there a way to fix this? Preferably permanently so that it doesn't happen again?

I made a character, and its one of my first times texturing, and I saved my character into a new folder, and when I came back to the model ALL the textures were pink, I used to know what to do, but I stopped texturing, how do I bring my textures back?


Consider a situation where a meeting is scheduled to start at 12:00 pm but one of the participants happens to appear at 12:15.   Did that individual come "in time" or "on time"? What's the difference between "in time" and "on time" as applied to this situation?

Which one is correct:        Submit your work in time.   Submit your work on time.


I'm facing a strange problem. When I try to backup or restore any database using a SQL Server user (not sa) that belongs only to "public" server role, i have the following error when i click the browse button on the "Select backup destination" window:  D:\SQLServerData\Backup Cannot access the specified path or file on the server. Verify that you have the necessary security privileges and that the path or file exists. ...  The user is db_owner for the database I try to backup, and SQLServer service is running with administrator account, so it should have no problems with access to the D:\SqlServerData\ folder.  I tried to add the user to any other server role, but none worked except "sysadmin". But having the user in sysadmin server role means that the user can do anything in any database, and I do not want that.  Any idea on what's going on?

I have a .bak file created today by someone else, manually created through SSMS 2008 R2. I'm trying to manually restore the database, unfortunately the file isn't appearing when I go to browse it.  I can script the restore process, but I've seen this problem before and I'm not sure what could cause the .bak to not appear.


I've noticed some authors of academic pieces tend to put square brackets around a T when starting a quote, I don't understand why.     "[T]he Organization is based on the principle of the   sovereign equality of all its Members."   Thanks!

What does the bracketed capital letter indicate in the revised version below? Is it essential, per the rules of proper punctuation, to do so? Are the ellipsis points (i.e., the spacing of the dots) spot on in that sentence to indicate the omission of one or more sentences?  Original quotation  "It need hardly be said that shortness is a merit in words. There are often reasons why shortness is not possible; much less often there are occasions when length, not shortness, is desirable. But it is a general truth that the short words are not only handier to use, but more possible in effect; extra syllables reduce, not increase, vigor."  Revised quotation  "It need hardly be said that shortness is a merit in words. . . . [S]hort words are not only handier to use, but more possible in effect; extra syllables reduce, not increase, vigor."  Thank you.


I'm trying to extract some information from a text.  The text I currently retrieve is some kind of horoscope, with by example:  Aries Some random text which is on multiple lines and could content one of the word above, as love for example. Love ★★★✩ Job ★★★✩ Energy ★★★✩ Libra Some random text which is on multiple lines and could content one of the word above, as job for example. Love ★★★✩ Job ★★★✩ Energy ★★★✩ Taurus Some random text which is on multiple lines and could content one of the word above, as energy for example. Love ★★★✩ Job ★★★★ Energy ★★★★   I've currently this regex to retrieve the differents values for one given sign:  Aries([\S\s]*)Love\s*([★✩]{1,4})\sJob\s*([★✩]{1,4})\sEnergy\s*([★✩]{1,4})   but the [\S\s]*is basically catching everything it can, and basically this match the whole text I gave in example.  So two possibility:   How to match the "smallest" expression possible? How to get the all the text on multiple lines without ALSO getting the Love/Job/Energy header+stars?   Thank you!!!

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


After commenting I get redirected to a white blank page.   App Version: 1.6.6.2 Device: iPhone 6s OS Version: Version 12.0.1 (Build 16A404)

Since iOS 11.2 all the way through 12.2 beta 4, if you post or discard a comment on any post on any SE community, the screen will turn white. This has been ongoing continuously for a year now, and it affects both the SE app and the SO app.   You can go back to the previous screen and open the question again, and everything appears as normal. You can also rotate the screen to get the text to come back. Using the arrows to navigate between the question and answers updates the HUD, but the screen remains white unless one of the above is done to get the text back.        UPDATE: After posting anything (comment, answer), the screen goes all white except for the sidebar. Perhaps it is intentional, but I prefer last week’s behavior of going back to the content. Not major, since the sidebar icons still work.


I have answered a question on stackoverflow with status of community wiki. Now I want to revert it as a user.   Is there any way to revert this answer to non-community wiki status ?

Possible Duplicates:             I added  and edited it to correct a mistake and add more information. It was made community wiki after 12 edits, but it is a regular answer. How can I undo this?


For the elliptic curve y^2 = x^3+2x+2 mod(23), why is it necessary that 23 is a prime. Why is the elliptic curve y^2 = x^3+2x+2 mod(24) not suitable for elliptic curve cryptography?

I come across this:     Numbers mod composite number does not form a field rather it forms a ring   and     every number has a multiplicative inverse under integer mod prime   Maybe these are the reasons why prime field is preferred? By the first above fact it means that construction of a composite field is not possible. But I have seen some research articles about multiplication algorithm using composite fields…  Why are elliptic curves constructed using prime fields and not composite fields?


I don't mean 1080p, but actual unscaled image size so when I set the wallpaper to an image with that size, it won't ask me to crop. It will fit without scaling.

On an Android phone the wallpaper spans across all of the home screens.  So what size should pictures be to fit properly as custom wallpapers?


What will happen to the force between two charged particles, if only one particle is placed inside the medium ? Like one in air and other one is in water( Or anything.. )

As far as I know, Coulomb's law of electrostatic force is applicable on two different charges situated in same medium. But if two individual charges are in different media (say one charge on a iron surface another on a plastic surface), then how does one calculate the force between them?  And if I have wrong conception , please correct me.


Everywhere I found that the definition of an injection only uses an implication. However, I can't think a case where if $f$ is an injective function, and if $a = b$, then $f(a) \neq f(b)$. Why do we use an implication ?

From wikipedia I obtain the following definition of an injective function :     Let $f$ be a function whose domain is a set $A$. The function $f$ is injective if for all $a$ and $b$ in $A$, if $f(a) = f(b)$, then $a = b$; that is, $f(a) = f(b)$ implies $a = b$.    From this I conclude that a function $f$ is injective if the below statement is true for all $a,b \in A$:  $$f(a)=f(b) \implies a=b$$  My question is: Can I re-formulate the above statement as $f(a)=f(b) \iff a=b$ ?


I have to show that $a_n=\left(1+\frac{1}{n}\right)^n$ is monotonic increasing. I struggle alot and tryng to find a right form to epxress that, $a_n\le a_{n+1}$ a little hint what might help would be great. Im in my first year in the introduction to real analysis, so tipps with derivative or more advanced arent usefull :/ I really only like to get a little hint :)

Show that $U_n:=\left(1+\dfrac{1}{n}\right)^n$, $n\in\Bbb N$, defines a monotonically increasing sequence.   I must show that $U_{n+1}-U_n\geq0$, i.e. $$\left(1+\dfrac{1}{n+1}\right)^{n+1}-\left(1+\dfrac{1}{n}\right)^n\geq0.$$  I am trying to go ahead of this step.


Suppose that $\displaystyle\sum_{n=1}^{\infty}\ a_n$ is absolutely convergent. How can we prove that $\displaystyle\sum_{n=1}^{\infty}\ a_n^2$ is convergent?

Let $\sum_{n=1}^{\infty} a_n$ be a series in R. Prove that if $\sum_{n=1}^{\infty} a_n$ is absolutely convergent, then $\sum_{n=1}^{\infty} (a_n)^2$ is convergent.


I have installed Joomla 3.3.6 on my ubnutu server 15.04 on cloud. I have noticed some script file created automatically which is sending some junk mail randomly. I have installed maldetect to check for malware.   Recent file detect was /var/www/html/joomla-test/libraries/joomla/observable/ini3.php  I have deleted this file now. But this type of script file created frequently. How to find from where this file created and delete permanently.  Do I need to move code to different server to get rid of this?.  Edit:  It is related to Joomla plugins I suspect. If we move our code to new server or install joomla again and install all necessary plugins and theme again same script might be created again.

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


I have alphanumeric numbers. After applying sorting thru SQL Server ORDER BY clause, I get following result  select *  from WO where WOCode = AnyNumber order by [ColumnName]   Result:  39660A1 39660A10 39660A11 39660A2 39660A3 39660A4 39660A5 39660A6 39660A7 39660A8 39660A9   Required result  39660A1 39660A2 39660A3 39660A4 39660A5 39660A6 39660A7 39660A8 39660A9 39660A10 39660A11

We have a large database on which we have DB side pagination. This is quick, returning a page of 50 rows from millions of records in a small fraction of a second.  Users can define their own sort, basically choosing what column to sort by.  Columns are dynamic - some have numeric values, some dates and some text.  While most sort as expected text sorts in a dumb way. Well, I say dumb, it makes sense to computers, but frustrates users.  For instance, sorting by a string record id gives something like:  rec1 rec10 rec14 rec2 rec20 rec3 rec4   ...and so on.  I want this to take account of the number, so:  rec1 rec2 rec3 rec4 rec10 rec14 rec20   I can't control the input (otherwise I'd just format in leading 000s) and I can't rely on a single format - some are things like "{alpha code}-{dept code}-{rec id}".  I know a few ways to do this in C#, but can't pull down all the records to sort them, as that would be to slow.  Does anyone know a way to quickly apply a natural sort in Sql server?    We're using:  ROW_NUMBER() over (order by {field name} asc)   And then we're paging by that.  We can add triggers, although we wouldn't. All their input is parametrised and the like, but I can't change the format - if they put in "rec2" and "rec10" they expect them to be returned just like that, and in natural order.    We have valid user input that follows different formats for different clients.  One might go rec1, rec2, rec3, ... rec100, rec101  While another might go: grp1rec1, grp1rec2, ... grp20rec300, grp20rec301  When I say we can't control the input I mean that we can't force users to change these standards - they have a value like grp1rec1 and I can't reformat it as grp01rec001, as that would be changing something used for lookups and linking to external systems.  These formats vary a lot, but are often mixtures of letters and numbers.  Sorting these in C# is easy - just break it up into { "grp", 20, "rec", 301 } and then compare sequence values in turn.  However there may be millions of records and the data is paged, I need the sort to be done on the SQL server.  SQL server sorts by value, not comparison - in C# I can split the values out to compare, but in SQL I need some logic that (very quickly) gets a single value that consistently sorts.  @moebius - your answer might work, but it does feel like an ugly compromise to add a sort-key for all these text values.


It's hard to explain the situation in title, so here it is:  I'm booking a 2 ways tickets from Singapore to Vietnam (Hanoi). However, i didn't board the trip Sing-Viet. Instead, I purchased another 1 way ticket, from Singapore to Vietnam with different time.  In that case, when I'm back from Vietnam to Singapore, the flight counter said, my tickets is not valid anymore, as i didn't take the 1st board,     Based on International Rules, they said.   So, Is my 2 ways tickets valid?

It seems like one-way tickets are always more expensive than buying round-trip. But what if I have two destinations? For example I would like to go on the following itinerary this March:  London --> Austin --> Rio de Janeiro --> London  At the moment the cheapest way to do this seems to be:  London --> Austin --> Rio de Janeiro --> Austin --> London  but that seems a bit ridiculous. Is there not a way to just buy a series of one way tickets that would follow the first itinerary? Please keep in mind, my main concern is price.


I have objects o1, o2,...,on and for each pair I calculate a value that measures the pair's difference. This is a percentage, so for example o1o2 differ by 56%. Now I want to cluster this data. I can see how a hierarchical clustering analysis would fit e.g. o5o6 are the closest pair, now which of the rest are closest to either o5 or o6, and so on.  My question is: can I apply a k-means analysis as well? It seems to me k-means requires (x,y) type data but I may be wrong. Perhaps k-means requires data with levels of measurement: (ratio, ratio) and hierarchical requires (nominal, nominal, ratio)? Or maybe there is a better technique?

Can anyone point me out a k-means implementation (it would be better if in matlab) that can take the distance matrix in input? The standard matlab implementation needs the observation matrix in input and it is not possible to custom change the similarity measure.


Hi new to python and programming in general  I'm trying to find an element in an array based on user input  here's what i've done   a =[31,41,59,26,41,58] input = input("Enter number : ") for i in range(1,len(a),1) :     if input == a[i] :        print(i)   problem is that it doesn't print out anything. what am I doing wrong here?

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python?


Suppose $G$ is a group. For each $g\in G$  we define the function $\phi_g(x) : G\to G$ as $\phi(x) = g^{-1}xg$. Prove that $\phi_g(x)$ is an automorphism of $G$. This is what I did ( But I don't know if it's right ): The only possibility for me that $\phi$ being an automorphism was if it's an identity function . So: $$\begin{align} \phi_g(g)& = g^{-1}gg\\  \phi_g(g) &= (g^{-1}g)g\\  \phi_g(g) &= eg\\  \phi_g(g)& = g. \end{align}$$ But at the same time this doesn't seem quite right for me...

Let $G$ be a group. By an automorphism of $G$ we mean an isomorphism $f: G\to G$ By an inner automorphism of $G$ we mean any function $\Phi_a$ of the following form: For every $x\in G$, $\Phi_a(x)=a x a^{-1}$. Prove that every inner automorphism of $G$ is an automorphism of $G$ which means I should prove $\Phi_a$ is isomorphism? any suggestion? thanks


I currently having an unused keyboard (a HP's KBRF1921 to be exact). I always need to type some Greek characters such as αβɣ and latin character as abc.   It'd be great if I could use one for latin and map another one for Greek. Having go to charmap or insert symbol everytime i want to type them is somewhat annoying all the times. There's already one asked here:  but the question is not currently answered yet and it's narrow for linux only and usb. My current keyboard uses PS/2 in order to save off some USB ports. And there's another one here:  but their solution is for games.   I'm using both Linux and Windows so what applies for either platform is welcome.

I'd like to use multiple keyboards (all USB or one USB and one PS/2) with a different keyboard layout on each. Is this possible in Windows 7 or XP?   I'd prefer to avoid a hardware-based solution if possible.  My specific issue is that I prefer to use a Dvorak layout, but most of my colleagues use QWERTY. I'd quite like it if they could use my computer with a QWERTY layout by using a second keyboard, without affecting the layout of the primary one.


I bag your pardon but I'm in need of any help. I must check String instance in C#. The String must contains only uppercase and lowercase English letters and '|' characters. How can I do this checking with Regex class in .NET Framework 4.5.? Suppose I got the String from Console:  String _processedString = Console.ReadLine();   How can I check it to according to above mentioned conditions?

I would like to have a regular expression that checks if a string contains only upper and lowercase letters, numbers, and underscores.


A designer did a design for me.  It is in Adobe illustrator.  In order to write my program, I need to export sublayers one by one to .png files.  How can I do that?

The title says it all, I want to know what the simplest way to export the selected objects.  In Inkscape, there is a menu option called export selected which does just this.    The aforementioned option lets you export the selection as a composite image or as a batch of individual images.  Both would be nice, but in this scenario I want to export the selected objects as a single image.  I can already create a new document, and paste in the selected items.  I am looking for a way that is easier than this.  How can I save / output / export only the objects I currently have selected, to an image file, in Adobe Illustrator CS5?


Why the slope will be infinitive if the tangent of curve is verticle ?  Suppose $x^2+2ax+y^2=0$ is a curve and its tangent is verticle to $x$-axis. From what basis we call the slope of this axis will be infinitive? Actually I searched a lot but didn't find any specific answer.  Thanks in advance

Find the slope of tangent line to the curve at the point $(1, \pi/2)$  the equation is  $$\sin(xy) = x$$  The right answer was = Slope is infinite   My answer was taking the derivative and I end up in this equation   $$ (1-y\cos(xy))/ x\cos(xy)  $$  I substitute with the points and the calculator showed an error, Does the error means infinite ?


Can someone just give me a simple example and simple explanation in words about what the difference is between pairwise and mutual independence?   I have this definition:   Three events $A,B,C$ are mutually independence iff the following conditions hold:   1) the events are pairwise independent   2) $P(A\cap B\cap C) = P(A)P(B)P(C)$

Would someone please advance/discuss some real-life situations falsities $1, 2$? I'd like to intuit why these are false. As a neophyte, since I still need to compute the probabilities for the examples in the two answers to apprehend them, I haven't naturalised these concepts yet. Thus, I beg leave to ask about other real-life examples which require less or no computations.  I tried and would appreciate less numerical examples than  and , and  Examples 1.22 and 1.23 on P39 of Introduction to Pr by Bertsekas.  $1.$ Pairwise Independence $\require{cancel} \cancel{\implies}$ (Mutual) Independence.      $2.$ Pairwise Independence $\require{cancel} \cancel{\Longleftarrow}$ (Mutual) Independence.         P38 defines (Mutual) Independence :    For all $S \subseteq \{1, ..., n - 1, n\} $ and events $A_i$, $Pr(\cap_{i \in S} A_i) = \Pi_{i \in S} A_i.$


I am working on proofs right now. I just came across the question stated in the title. The main question I have is, does the number of elements in a set matter for equality if all elements in both sets are equal? Since 2 is a member of both sets A and B, and the only element(s) in both A and B is 2, it seems this definition of set equality would hold. Am I wrong?

Is there any book that explicitly contain the convention that a representation of the set that contain repeated element is the same as the one without repeated elements?  Like $\{1,1,2,3\} = \{1,2,3\}$.  I have looked over a few books and it didn't mention such thing. (Wikipedia has it, but it does not cite source).  In my years learning mathematics in both US and Hungary, this convention is known and applied. However recently I noticed some Chinese students claim they have never seen this before, and I don't remember I saw it in any book either.   I never found a book explicitly says what are the rules in how $\{a_1,a_2,a_3,\ldots,a_n\}$ specify a set. Some people believe it can only specify a set if $a_i\neq a_j \Leftrightarrow i\neq j$. The convention shows that doesn't have to be satisfied.


What is the origin of the Millennium Falcon's name,  within Disney canon?  Obviously the falcon is in reference to the bat-falcon (as per ) but what about the 'millennium' part?

I'm particularly interested in how the "Millennium" part pertains to the ship itself. It wouldn't hurt to explain the "Falcon" part either though.


Prove that for all  $ \epsilon > 0, \epsilon \in \mathbb{R} $ for every $ x, y \in \mathbb{R} $ if $ | x - y | < \epsilon \iff x = y$  (this question has similar ones in, but this one has the full proof, not only the hint).

I have to do this exercise for my math study, and I'm having trouble with doing the second part of it.  Let $x, y, \epsilon \in \mathbb{R}$ and $\epsilon > 0$. Prove: $|x - y| \leqslant \epsilon$ $\forall \epsilon > 0 \Leftrightarrow x = y$  I think I have the left implication $\Leftarrow$:  Assume $x = y \Rightarrow x - y = 0 \Rightarrow|x - y| = 0 = |0| \Rightarrow|x - y| = 0 < \epsilon \Rightarrow |x - y| \leqslant \epsilon$ $\forall \epsilon > 0 \in \mathbb{R}$  Is this argument correct?  For the right implication, I do only have an idea of how to prove it. I think I have to assume first that $x > y$ and then $x < y$ and get a contradiction form both.   Could you please explain me the right implication and tell me if my left implication is correct?  Thanks in advance!


Pattern p = Pattern.compile("^[0-9]{0,3}$"); Matcher m = p.matcher(in); if (m.find()) {     JOptionPane.showMessageDialog(null, " 4 integers please"); }  It is a button that adds numbers Trying to create exception that limits amount of numbers in dialog , it detects if the number is within the limit but does not stop the program.

It is discouraged to simply catch System.Exception. Instead, only the "known" exceptions should be caught. Now, this sometimes leads to unnecessary repetitive code, for example: try {     WebId = new Guid(queryString["web"]); } catch (FormatException) {     WebId = Guid.Empty; } catch (OverflowException) {     WebId = Guid.Empty; }  I wonder: Is there a way to catch both exceptions and only call the WebId = Guid.Empty call once? The given example is rather simple, as it's only a . But imagine code where you modify an object multiple times, and if one of the manipulations fails expectedly, you want to "reset" the object. However, if there is an unexpected exception, I still want to throw that higher.


Is there a way to constraint a generic type to only integral type?  In example, if I have a method  T[] sort<T>(T[] data) where : T ... {}   what would I put as constraint if I wanted to ensure the parameter will be some sort of integral type?  I have tryed looking at  however it does not seem to mention anything about constraining and primitive types.  Thank you for your help.

Can anyone tell me if there is a way with generics to limit a generic type argument T to only:   Int16 Int32 Int64 UInt16 UInt32 UInt64   I'm aware of the where keyword, but can't find an interface for only these types,  Something like:  static bool IntegerFunction<T>(T value) where T : INumeric


Does a Canadian passport holder need a transit visa for a London transit when traveling from Nigeria to Toronto, Canada?

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


I have a 240 GB SSD in which I have already installed Ubuntu. But now I have to dual boot with Windows10. But I'm unable to create a partition.

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


I'm just a layman with no real science background  (a) I'm not really sure what a shadow is. Some people are saying that it's the absence of something (a photon?) and therefore it is not subject to laws of physics. But I know when I'm in a shadow and when in sunlight... that's "information", and I thought that information flow can't break the speed of light limit.  (b) Some others use the laser pointer/flicking wrist example to talk about laser dots moving faster than light speed. But that can't be right, can it? The photons from the laser point have to travel from A to B and (after wrist flick) from A to C ... but the photons are all moving at the speed of light - there's no law-breaking in moving the laser dot from point B to point C because the photons are moving either from A to B or A to C ... the distance from B to C is not material (is it?).  (c) Also, can a shadow be thought of as a gap in a photon flow? E.g. if I interrupt a beam of single photons then can I think of it as e.g. PPPSSSPPPSSSPPPSSSPPP, etc where P = photons and S(shadow) = no photon &, if so, the "SSS" is effectively travelling at the speed of light ... no faster.

I have seen many folks doing this  concluding that shadow from point A on the Moon can travel to point B on the Moon faster than light.  What I fail to understand here (and I am sure I am wrong), is nothing can travel faster than light. I also read about Relativity where Einstein stated that every event happening for you depends on how fast the light gets from where the event is happening to you.  This is my particular problem with this Moon shadow experiment. You cannot make a shadow travel faster than light, because in order for the "disappearance" of light to get to the Moon, it has to travel at light speed.  Here is one way to understand my point. Consider we shine a flashlight on Moon, like the guy in the linked video did, we move the finger across the face of the flashlight, before we moved the finger it was casting the shadow at Point A on Moon, after we finish moving our finger, the shadow is at Point B on the Moon.  When the finger reaches the end of it's moving length, the light waves that have left the flashlight before the finger reached there will have to hit Point B and it will take them a second and a half to get there, and another second and half for us to see that shadow on point B, which makes it 3 seconds + finger moving time for us to actually see the shadow at point B. That means shadow traveled (say) across the diameter of the Moon in 3 seconds.   So. about 3000 Km in ~3 seconds make it 1000 Km per seconds which is very tiny compared to the speed of light. How can these experiments conclude that Shadow could be made to travel faster than light? What is the obvious clue that I am missing here?


I am new to all of this.  I have just bought a new HP Proliant Gen8 G2020T microserver. I want to install Ubuntu 12.04 i386 version on the server. I have downloaded Ubuntu 12.04 on a USB from this link:   Is this the right version?  I have powered the server and I get an option of F9 or F10. Which one do I choose?  Could you please give me step by step instructions?  Your help is appreciated in advance.

I'd like to install Ubuntu server on my machine, is there a step-by-step instructions on how to accomplish that or a guide that will just go through the basic steps of installing Ubuntu Server from beginning to end.  Instructions originally for 13.04.


One of my answers has been deleted, but I'm not able to find which one it is and why.  Is there any way to find to which answer it was, and why it got deleted from my SO account?  I had 187 answers but now it's 186.    I can't see any rep change in the rep history either.

Today, I saw -50rep added to my reputation in my Movies.SE account, as a result of deletion of a user. So definitely one or more answers to his question(s) was/were deleted. So is there a way to see the deleted posts?


How do I see the answers that I gave earlier. This is because I gave an answer to a question long ago but I need to revisit that concept.  Note: user:me technique doesn't work for answers one has given, it only works for questions.

I want to see all my Questions and Answers in a particular SE site -  - profile page through Stack Exchange Android App. How can I see that? When I tried to see that I found only Top Posts(5) and Top Tags.


I've been researching this and attempting for hours. I've taken after this post for an example of how to pass arguments to a fragment:    I'm trying to pass a custom object from an activity, to a fragment. I chose to implement serializable and pass the object using:  bundle.putSerializable("key", Serializable).   I'm getting the error     java.lang.NullPointerException: Attempt to invoke virtual method java.io.Serializable android.os.Bundle.getSerializable(java.lang.String) on a null object reference   when I'm trying to set my object equal to the arguments passed in from the activity.  here is my object  public class Player implements Serializable {     int attack;    private int tempAttack;    int defense;    private int tempDefense;    int pop;    int level;    String t1Evo;    String t2Evo;    String t3Evo;     public Player() {       attack = 0;       tempAttack = 0;       defense = 0;       tempDefense = 0;       pop = 20;       level = 1;       t1Evo = null;       t2Evo = null;       t3Evo = null;    } }   Then here is my activity from which I am passing, I eventually want to pass all four of my objects, but I right now I'm trying to get at least one to successfully pass.  public class GameScreen extends FragmentActivity {  // Anytime you need to grab data from the players, // this screen will hold them.     private Player player1;    private Player player2;    private Player player3;    private Player player4;      @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.activity_game_screen);         // Instantiate the player objects        player1 = new Player();        player2 = new Player();        player3 = new Player();        player4 = new Player();         // put the objects to send to our fragment in a bundle        PlayerInformation newFragment = new PlayerInformation();        Bundle args = new Bundle();        args.putSerializable("Player1", player1);        newFragment.setArguments(args);         // start transaction        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();         // Replace whatever is in the fragment_player_information view with this fragment,        transaction.add(R.id.playerInformation, newFragment);        transaction.commit();    } }   And then the fragment which throws the Null Pointer Exception, I've indicated the line with "-->"     package com.cs246.spencer.naturalselection;  import android.app.Activity;  import android.content.Context; import android.content.Intent; import android.net.Uri; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView;  import java.io.Serializable;   /**  * Fragment that displays the Player information on GameScreen  */ public class PlayerInformation extends Fragment {    Context context;    Player player1;    Player player2;    Player player3;    Player player4;     public PlayerInformation(){        this.context=context;    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                          Bundle savedInstanceState) {        // grab the objects passed from GameScreen        Bundle args = getArguments();    --> player1 = (Player) args.getSerializable("Player1");        player1 = (Player) getArguments().getSerializable("Player1");         // Inflate the layout for this fragment        return inflater.inflate(R.layout.fragment_player_information, container, false);    }     public void Update() {        TextView player1Pop = (TextView) ((Activity)context).findViewById(R.id.player1Pop);        player1Pop.setText(player1.pop);    } }

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


I have searched this problem online but could not resolve it. Excuse my inexperience.  I am trying to run a python script on startup which uses PyQt5 library to create a window. I am using a raspberry pi 3 model b+, and raspbian buster with lxde. I wrote a shell script as follows:  #! /bin/bash sleep 10 python3 /home/pi/Desktop/workfolder/mainwindow.py   Then I have added this into crontab.  @reboot /home/pi/Desktop/workfolder/startup.sh > /home/pi/Documents/error.log 2>&1   When I reboot, error log gives me the following error.  qt.qpa.screen: QXcbConnection: Could not connect to display Could not connect to any X display.   I had some other issues which I was able to solve but I am stuck at this one. When I run my script via terminal, my screen does start. As far as I know, Xorg is installed since lxde is running.  I have also changed sleep 10 to sleep 30 to make sure if script was not running too early. But still gives the same error.

I need to run shell script contains Xdotool codes in /home/z/Desktop/tempo/run.sh. I've tried many ways of DISPLAY=:0 but always not works.  I've tried each of below codes, and not works:  * * * * * export DISPLAY=:0 cd /home/z/Desktop/tempo; ./run.sh * * * * * export DISPLAY=:0; cd /home/z/Desktop/tempo; ./run.sh * * * * * export DISPLAY=:0 && cd /home/z/Desktop/tempo; ./run.sh * * * * * DISPLAY=:0 cd /home/z/Desktop/tempo; ./run.sh * * * * * DISPLAY=:0; cd /home/z/Desktop/tempo; ./run.sh * * * * * DISPLAY=:0 && cd /home/z/Desktop/tempo; ./run.sh   Running directly also not works:  * * * * * export DISPLAY=:0 xdotool mousemove 20 20 * * * * * export DISPLAY=:0; xdotool mousemove 20 20 * * * * * export DISPLAY=:0 && xdotool mousemove 20 20 * * * * * DISPLAY=:0 xdotool mousemove 20 20 * * * * * DISPLAY=:0; xdotool mousemove 20 20 * * * * * DISPLAY=:0 && xdotool mousemove 20 20   I always don't see my mouse moving on each line of codes above.  I've also tested Xdotool codes to make invalid website URI request and see the logs. Sadly the logs still blank.


A pump house is to be placed at some point $X$ along a river, A pipe from point $A$ and a pipe from point $B$ will then be connected to the point $X$. How far should $X$ be away from $M$, so that the total length of the pipes $\overline{AX}$ and $\overline{BX}$ are minimised?    I just need help with setting up the function.

There are two poles (lets say poles A and B) $50$ feet apart and the poles are $15$ and $30$ feet tall. There is a wire which runs from the top of pole A to the ground, and then to the top of pole B so that two triangles are made. What is the minimum length of wire needed to set up this configuration?   I tried finding this by setting up an equation for the length of the wire and taking the first derivative, but I ended up with an ugly polynomial.   I also tried drawing in one more triangle and used the law of cosines, but that didn't turn out too well either.   The most likely source of this problem (altough it had different numbers) is from "Maxima and Minima Witouth Calculus" by Ivan Niven, but I'm not sure.


I noticed that my app only when is closed by system during open there is nullpointexception.  Look I have Activity here I get data form db and create an object. Then I create new Fragment and set before created object to frament by setter.  And use fragment manager to display fragment.  Any here is a problem because in onCreate method field with my object is null.  I am sure I seted object and it wasnt null.   Activity where I get data from db and create Fragment  public class ActivityForSingle extends AppCompatActivity {   Employee emloyee;    protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_for_single);     ...      getEmployee(); // here I get emplyee from db and create employee object      SitePersonFragment f = new SitePersonFragment();             f.setEmpoyee(employee); // here emplyee is not null             getSupportFragmentManager().beginTransaction().add(R.id.frameForFragment, f, "USER_SITE").commit();   }   public class SitePersonFragment extends Fragment implements Update, DatePickerDialog.OnDateSetListener {   Employee employee;    setEmployee(Employee e){       this.emplyee = e;   //here e and employee is not null    }    @Override      public void onViewCreated(View view, Bundle savedInstanceState) {     super.onViewCreated(view, savedInstanceState);    //here employee is null   // why??  }   What happend?  I cannot debug because app is  destroyed.


I am wondering how to spawn an entity behind another one but it does it based on where the entity is facing

I'm trying to create a jetpack with the new elytra by summoning in exploding creepers behind you to boost you, but I can only do it in one direction. I'm using this command:  /execute @e[type=Player,name=CheeseTruffles] ~-4 ~ ~ summon Creeper ~ ~ ~ {Fuse:0}   But it only hits you in one spot. Is there anyway to make the summoning location depend on the place you're looking?


I am writing a Tic Tac Toe game with two files, one for a TTT object, and another for the main method to run the actual game. Everything is working fine except for my win/draw method. I am creating strings out of all the possible winning lines which is also working correctly. However, my logic to return an "X" or an "O" is not functioning properly. In my main method for the game, I can print a win combination and it will successfully print either an "XXX" or an "OOO" but the method isn't correctly recognizing that and using it for the conditions. Pseudo for win/draw method: Create 8 different strings from each winning combination Check if any of them are equal to "XXX" or "OOO" if so, return "X" or "O" public class TicTacToe {  //Enum data type for board states public enum states {      X,     O,     EMPTY;      } //2D Array for board private static states[][] board = new states[3][3];  //Method constructor public TicTacToe() {     for(int i = 0; i < 3; i++) {         for(int j = 0; j < 3; j++) {             board[i][j] = states.EMPTY;         }     }    }  //Method to display the board in console public void displayBoard() {     System.out.printf("%5s  %5s  %5s\n\n%5s  %5s  %5s\n\n%5s  %5s  %5s\n\n",              board[0][0], board[0][1], board[0][2],             board[1][0], board[1][1], board[1][2],             board[2][0], board[2][1], board[2][2]);                                                  }  //Method to set a board position to X or O public void setBoard(int row, int column, states i) {     if (board[row][column] == states.EMPTY) {         board[row][column] = i;     }     else {         throw new RuntimeException();     }   //Method to check for a winner or draw public String winDraw() {     String row1 = board[0][0].toString() + board[0][1].toString() + board[0][2].toString();     String row2 = board[1][0].toString() + board[1][1].toString() + board[1][2].toString();     String row3 = board[2][0].toString() + board[2][1].toString() + board[2][2].toString();     String col1 = board[0][0].toString() + board[1][0].toString() + board[2][0].toString();     String col2 = board[0][1].toString() + board[1][1].toString() + board[2][1].toString();     String col3 = board[0][2].toString() + board[1][2].toString() + board[2][2].toString();     String diag = board[0][0].toString() + board[1][1].toString() + board[2][2].toString();     String antiDiag = board[0][2].toString() + board[1][1].toString() + board[2][0].toString();          if(row1 == "XXX" || row2 == "XXX" || row3 == "XXX" || col1 == "XXX" || col2 == "XXX" || col3 == "XXX" || diag == "XXX" || antiDiag == "XXX") {         return "X";     }     else if(row1 == "OOO" || row2 == "OOO" || row3 == "OOO" || col1 == "OOO" || col2 == "OOO" || col3 == "OOO" || diag == "OOO" || antiDiag == "OOO") {         return "O";     }     else {         return null;     } }  }

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


I flagged , which was marked as helpful. So why does this post still exist?  Someone edited the post a few minutes back, so here's the original revision that I flagged:     Could you try with android:showAsAction="always" for the items in the menu.   I think this should be a comment.   If you are saying that I was wrong to flag this as "not an answer" then why did a moderator mark it as "helpful"?

I flagged a post and (choose one)   my flag was marked as helpful, yet nothing was done my flag was marked as declined, yet the post was deleted/edited/closed   Why?


Interaction causes change and that change can be measured, so shouldn't everything be measured constantly

Let's say we are doing the double slit experiment with electrons. We get an interference pattern, and if we put detectors at slits, then we get two piles pattern because we measure electrons' positions when going through slits. But an electron interacts with other particles in a lot of different ways, e.g. electric field, gravity. Seems like the whole universe is receiving information about the electron's position. Why is it not the case and the electron goes through slits "unmeasured"?  Bonus question: in real experiments do we face the problem of not "shielding" particles from "measurement" good enough and thus getting a mix of both patterns on the screen?


I have a program that reads user input—moves, it's a boardgame—from the user. Like so:  $ game enter your move:  # etcetera   The first N moves I need to repeat each time, so I put them in a text file, one line each. That works:  $ game < moves.txt   This works, but after these N moves, how do I return to input from the command line?  I realize this is probably a duplicate question, but I couldn't find it.

Consider the interactive program interactive. I have to run this program fairly frequently, and each time I run it the first few commands are the same. Obviously, having to type those commands over and over again is a pain. I have collected those command (separated by newlines) in the file cmd. Now I can do cat cmd | interactive to run the commands. The problem is that once cmd has been fully read, interactive recieves EOF and exits.  What I wish to do is first have interactive read from the pipe (obviously interactive < cmd is also acceptable) and when EOF is received, start reading from the keyboard instead.


I read some articles which claim that after each workout, we should have at least one hour's rest before meal; others suggest half an hour. Otherwise, it will do damage to one's stomach. These were in Chinese; I haven't found any English articles talking about this.   Does having a meal shortly after workout cause any harm to one's stomach? If so, what is the time period one should wait before eating?

It is  that, after eating, you should wait 2-3 hours before exercising. It isn't recommended to eat and right afterwards to exercise (or swim).  But I haven't really understood why that is. Does this bad behavior affect me immediately (if I'm in robust health) or does it affect me in the long term? Αnd how?


In a short circuit, the potential difference across the terminals of a battery (consider a single cell with internal resistance)is 0 according to the equation  $$V=E-Ir,$$ where $r$ is internal resistance of the cell,$E$ is the emf of the cell and $V$ is a potential difference across the battery.   If the potential difference across any two points in a circuit is 0, the electric current $I$ doesn't flow right? Then how does current flow in a short circuit (assume 0 resistance for short-circuited wire)?

I know the path of least reisistance has been clarified already However, to derive the equations you need to assume that the voltage of each parallel component is equal. But we know for a short circuit current the voltage is zero (By Ohm's law!) So there is a glaring contradiction!


I have found closely related questions on StackExchange, but (surprisingly) not this exact question.  Seems some answers say individual photons do not have amplitude, only when traveling with other photons, forming a wave.  But even then, can't the amplitude be measured?  If so, what are the range of amplitudes and how do they vary?  Based on the frequencies and energies of the light?  Does higher frequency correspond to lower amplitude?  Moderators: This question is not a duplicate to this question:   That prior question is more about the formula for calculating electromagnetic energy amplitude of a single photon. My question is about an experimental way to MEASURE the positional (x) amplitude of the wave passing through a specific apparatus.  Two very different things.  Thanks.  I have updated my question to a more specific thought experiment:  If you had a vertical slit with a horizontal width that could be varied, and you passed horizontally polarized light through this slit, wouldn't the slit block any photons from passing through it if the width of the slit was smaller than the amplitude of the light waves?  Wouldn't we at least get a predicted or average amplitude, even with uncertainty principle?  Wouldn't the energy/frequency/wavelength of the wave also have some correlation to the amplitude?

Given a light pulse in vacuum containing a single photon with an energy $E=h\nu$, what is the peak value of the electric / magnetic field?


I have very little bluetooth expertize. All I want to do is to occasionally be able to use my computer's speakers and microphone for phone conversations. I don't want to use a bluetooth headset.   All tutorials I can find on the Net are either dated for Ubuntu 12.04 at the very latest, or describe the process of connecting to the bluetooth headset.   I have Ubuntu 14.04 64bit Asus N56VZ notebook with built-in bluetooth device, that works well under Ubuntu.   My phone is Nokia 6310i, and is compatible with bluetooth headsets. I know how to connect this phone to the dedicated headset. I just don't know how to connect it to my notebook for the same purpose.    When I initiate connection from my mobile to the notebook, or initiate connection from my notebook to the mobile or just turn off the bluetooth and the mobile altogether I've got the same, list sources (obtained via pactl list sinks and pactl list sources and filtering out all other fields):  Sink #0     Name: alsa_output.pci-0000_00_1b.0.analog-stereo Source #0     Name: alsa_output.pci-0000_00_1b.0.analog-stereo.monitor Source #1     Name: alsa_input.pci-0000_00_1b.0.analog-stereo   I guess one don't "just connect" to the mobile without some extra preparation. The connection connects, and after a second disconnects. I guess I need to make the computer to advertise itself as a headset, otherwise the phone might think it is something different and it doesn't want to deal with it.   This is my /etc/bluetooth/audio.conf. By manipulating its contents I never saw any effect (and of course I did reboot after each change), so maybe this file is depreciated. Or the effects are too subtle for me to see.   [General] AutoConnect=true Enable = Sink,Source,Gateway  [Headset] HFP=true MaxConnected=1 FastConnectable=false  [A2DP] SBCSources=1 MPEG12Sources=0

I am trying to use a Bluetooth headset on an Ubuntu PC. I am able to connect phone to pc via BT. I can stream music to PC. But cannot hear call audio. I have checked in Android phone logs, and BT sco link is established. But when making a call or virtual call (play audio through sco path in Android phone) the audio is not audible in PC headset. SCO packets are NOT appearing in btmon logs either. Anyone successfully done this?  version- ubuntu 16.04 Installed- bluez, ofono, pulseaudio pactl sink: Name- bluez_sink.22_22_8E_DE_B9_2B,             Name: alsa_output.pci-0000_00_1b.0.iec958-stereo pactl source: Name-bluez_sink.22_22_8E_DE_B9_2B.monitor               Name: alsa_input.pci-0000_00_1b.0.analog-stereo


I am interested in learning Bayesian Statistics related for my CS career. I have a very little background on frequentist statistics, which I know differs from the bayesian approach. The reason of my interest is because I would like to apply some techniques such as mixture of Gaussians, or EM algorithms.  I have seen that before studying Bayesian Statistics it is advisable to learn concepts like probability distributions, pdf, cdf, maximum likelihood, moments, and so on. Does anybody has a recommendation about what topics to read first before doing Bayesian Stat? also what book do you recommend for these preliminars?  PD. Apart of the bayesian stuff, any book that could be good for learning basis statistics and probability that I would need for the bayesian part?

Which is the best introductory textbook for Bayesian statistics?  One book per answer, please.


I am really lost trying to understand the difference between the logical connective "implies", $\to$, and the metalogical symbol (or maybe it's also a connective?) $\vdash$. (This is all focusing on prepositional logic here).  In metalogical terms, for example with modus ponens, it is said that $P, P \to Q \vdash Q$, which means "If we have a proof of $P$, and we have a proof of $P \to Q$, then we can infer / make a proof of $Q$". But I don't understand what the difference is between that and saying something like $P \land (P \to Q) \to Q$ which is similar but uses $\to$ instead of $\vdash$.  For example the $P \to Q$, at least in my experience, means "it is possible to go from $P$ to $Q$" but I don't see how "going to $Q$" is different from "inferring $Q$." Simply telling me that one is metalogical and one is not doesn't really help me understand what's going on.   I've also been given the example of  but I don't understand this, either. It sounds like the tortoise is constantly rejecting implications because "who says I have to accept conclusions just because the premises are true?" but then somehow introducing a metalogical $\vdash$ solves this? "We use the metalogical symbol $\vdash$ to basically force that stubborn tortoise to accept the conclusions and we've now circumvented the issue."  Unless I've grossly misunderstood something I just don't see why that's even a thing. Who says then I have to accept $\vdash$? Is $\vdash$ just a stronger form of $\to$, like a "sudo $\to$" or something (to borrow a Linux term), a form of implies that forces the conclusion to be accepted from the premise(s)?   What's the difference? How are they working here? Why do we need them? Are there any concrete examples showing the difference of both?

In Wikipedia,  in the last axiom of the Natural deduction system, it says "From [accepting $p$ allows a proof of $q$], infer $(p \to q)$." Isn't that a tautology? In the big table "Basic and Derived Argument Forms" that follows, I see it using a new symbol "$\vdash$" to express "therefore". Isn't that something can be done by the symbol "$\to$"? For example, what's the difference between "$(p \land q) \vdash p$" and "$(p \land q) \to p$"?  An interesting symbolic representation of the last axiom of NDS is that $(p \vdash q) \vdash (\vdash p \to q)$. Which I don't understand why is made so complicated.    What also puzzles me is in the  that follows. Since you list "$A$" as a promise, which is basically saying "assuming $A=\text{True}$", then why you have to go around such a big circle, using disjunction, conjunction, and conjunction elimination to prove back that "$A$" is true? If it is me, I would say "assuming $A=\text{True}$, we will know that $A=\text{true}$. Bang! Now we get $A \vdash A$, so we have $\vdash A \to A$." What's wrong in this deduction?


Using Newton's binomial theorem to argue that: $n \ge 1$ $$36^n - 26^n = \sum_{k=1}^{n}\binom{n}{k}10^k \cdot 26^{n-k}$$                               my argument $$(26+10)^n = \sum_{k=1}^{n}\binom{n}{k}10^k \cdot 26^{n-k} +26^n $$ $$(26+10)^n = \sum_{k=0}^{n}\binom{n}{k}10^k \cdot 26^{n-k} +26^n $$  I'm stuck at the part on what to do with the $26^n$ After I moved it over a made the sum $\sum_{k=1}^{n}$ to $\sum_{k=1}^{n}$

Let $ n \ge 1 $ be an integer. Use newton's Binomial Theorem to argue that  $$36^n -26^n = \sum_{k=1}^{n}\binom{n}{k}10^k\cdot26^{n-k}$$  I do not know how to make the LHS = RHS. I have tried $(36^n-26^n) = 10^n $ which is $x$ in the RHS, but I don't know what to do with the $26^{n-k}$ after I have gotten rid of the $26^n$ on the right. I also know I might have to use $\binom{n}{k} = \binom{n-1}{k-1} + \binom{n-1}{k}$ pascal's identity in this question.  Maybe I am approaching it from a completely wrong point of view, If someone can help point me in the right direction. It would be much appreciated!!!


I was trying to create a new Mongodb instance based on my old Mongo Database. In my current DB I have an user and password configured. So, I can access my database using:  $ mongo --host $MONGO_HOST -u $MONGO_USER -p $MONGO_PASSWORD --authenticationDatabase admin   This works perfectly. But accidentally, I typed:   $ mongo --host $MONGO_HOST --authenticationDatabase admin   And this is when the problem came in! The MongoDatabase authorized my connection for the database!  The security.authorization is set as true in my mongod.conf. Is this a weakness in MongoDB? Is there any method to always force the authentication?  EDIT 1: Current configuration for mongo:  {     "config" : "/etc/mongod.conf",     "net" : {         "bindIp" : "0.0.0.0",         "port" : 27017     },     "security" : {         "authorization" : "enabled"     },     "storage" : {         "dbPath" : "/var/lib/mongodb",         "journal" : {             "enabled" : true         }     },     "systemLog" : {         "destination" : "file",         "logAppend" : true,         "path" : "/var/log/mongodb/mongod.log",         "quiet" : true     } }

If to run mongo with authorization (i.e mongod --auth) it still allows to connect using client mongo and get to mongo cli where one will get refused to execute any command.  But I wonder if it is possible to close such connection for the unauthenticated user so one does not see mongo cli at all?


I have someone asking for an integration of $\int \sin^n x$. I have little to no knowledge of integration, so can someone help?  To be clear, I need a solution understandable for a sophomore or thereabout who knows integration.

I am working on trying to solve this problem:     Prove: $\int \sin^n{x} \ dx = -\frac{1}{n} \cos{x} \cdot \sin^{n - 1}{x} + \frac{n - 1}{n} \int \sin^{n - 2}{x} \ dx$   Here are the steps that I follow in the example that I am reading:     $u = \sin^{n - 1}{x}$      $du = (n - 1) \cdot \sin^{n - 2}{x} \cdot \cos{x} \ dx$      $v = -\cos{x}$      $dv = \sin{x} \ dx$            $\int \sin^n{x} \ dx =  \sin^{n - 1}{x} \cdot \sin{x} \ dx$      $\int \sin^n{x} \ dx = \underbrace{\sin^{n - 1}{x}}_{u} \cdot \underbrace{-\cos{x}}_{v} - \int \underbrace{-\cos{x}}_{v} \cdot \underbrace{(n - 1) \cdot \sin^{n - 2}{x} \cdot \cos{x} \ dx}_{du}$      $\int \sin^n{x} \ dx = -\cos{x} \cdot \sin^{n - 1}{x} + (n - 1)\int \sin^{n - 2}{x} \cdot \cos^{2}{x} \ dx$      $\int \sin^n{x} \ dx = -\cos{x} \cdot \sin^{n - 1}{x} + (n - 1)\int \sin^{n - 2}{x} \cdot \left(1 - \sin^{2}{x}\right) \ dx$   Here is where I get lost. How did we go from $\int \sin^{n - 2}{x} \cdot \left(1 - \sin^{2}{x}\right) \ dx$ to $\int \sin^{n - 2}{x} \ dx - (n - 1) \int \sin^{n}{x} \ dx$? Even more specifically, where did $\sin^{n}{x}$ come from?     $\int \sin^n{x} \ dx = -\cos{x} \cdot \sin^{n - 1}{x} + (n - 1)\int \sin^{n - 2}{x} \ dx - (n - 1) \int \sin^{n}{x} \ dx$   I get this part.     $n\int \sin^n{x} \ dx = -\cos{x} \cdot \sin^{n - 1}{x} + (n - 1)\int \sin^{n - 2}{x} \ dx$      $\int \sin^n{x} \ dx = -\frac{1}{n} \cos{x} \cdot x \ \sin^{n - 1}{x} + \frac{n - 1}{n} \int \sin^{n - 2}{x} \ dx$   Could someone please explain what I am missing?  Thank you for your time.


I am using Tasker.  How do i get my phone to turn wifi off when signal is low and turn data back on.  I also want it to check occasionally for a stronger signal.

When the WiFi signal strength is low, the phone switches to a 4G network. When the WiFi signal strength is high, the phone switches to that WiFi network.   This is normal behavior for any Android device and all too familiar to Android users, or to users of any WiFi enabled device in fact. But the problem I often run into is that the WiFi signal is too low to be usable, and too high to switch to 4G automatically.   WiFi signal strength 0 < x < 0.5 marks (bars), the phone switches to a 4G network. WiFi signal strength x > 0.5 marks, the phone switches to that WiFi network.   These values are not real measurements. They are merely my own perceived points at which the phone switches between the two.  TL;DR: Is there a way for me to optimize the auto-switching between WiFi and 4G to my own liking? Is it possible to set that threshold point manually? What I would like is to switch over to 4G as soon as the WiFi signal is below the 2 mark point.    What I am often forced to do, in order to get (usable) Internet access, is to enter the Settings menu on the phone and disable WiFi altogether in order to force my "smart" phone to switch over to 4G!  Would it not be better if the user could control the threshold at which the phone switches between WiFi and 4G? I think the default threshold is too conservative. It's set up to conserve 4G bandwidth by free-riding on available WiFi networks for as long as possible and whenever possible (available).  Devices are optimize to make use of WiFi as much as possible, due to associated data costs on 4G networks. But this is a nuisance! My Internet access is almost completely crippled for many of the WiFi networks I have access to, whenever the signal strength is below the 2 mark point. On the other hand, I have over 4 GB unused bandwidth on my carrier network, for which I have a much stronger signal, but I have to disable WiFi first in order to connect to 4G. That's not convenient when you're on the move a lot.  I have recently started using the 4G network almost exclusively. I have stopped using WiFi because I have had enough with enabling and disabling it back and forth, and having to remember to do it when I'm on the move. So I am looking for a more permanent solution to this.


Let $R$ be the ring of all the real valued continuous functions on the closed unit interval. Show that $ M=\{ f\in R:f(1/3)=0 \} $ is a maximal ideal

I would like to compile all questions I have encountered with Ideals in the ring $\mathcal{C}[0,1]$ of all continuous real valued functions and ask if there are any gaps.  Question is to see if :     the ideal $\mathcal{I}=\{f\in \mathcal{C}[0,1] : f(0)=0\}$ is maximal ideal in the ring $\mathcal{C}[0,1]$ of all continuous real valued functions.   What I have done so far is :  consider $\eta :\mathcal{C}[0,1]\rightarrow \mathbb{R}$ where $f\rightarrow f(0)$   $Ker (\eta) = \{ f\in \mathcal{C}[0,1] : f(0)=0\}$  I could see that for each $r\in \mathbb{R}$, I would set $f$ such that $f(x)=x+r$  So, $\eta$ is surjective.  So, I would get $\mathcal{C}[0,1]/\mathcal{I}\cong \mathbb{R}$  As $\mathbb{R}$ is a field so ia the quotient $\mathcal{C}[0,1]/\mathcal{I}$ which means that $\mathcal{I}$ is an ideal in $\mathcal{C}[0,1]$.    Now Another Question on same idea :  Question is to see if :     the ideal $\mathcal{I}=\{f\in \mathcal{C}[0,1] : f(0)=f(1)=0\}$ is maximal ideal in the ring $\mathcal{C}[0,1]$ of all continuous real valued functions.   I thought of using same ideas as above but i am unable to choose perfect $\eta$  I believe that this is not even a prime ideal..  I set  $f(x)=x$ and $g(x)=x-1$ and consider $f(x)g(x)=(x)(x-1)$ then,   $(fg)(0)=f(0)g(0)=0.(-1)=0$   $(fg)(1)=f(1)g(1)=1.0=0$  So, $fg\in \mathcal{I}=\{f\in \mathcal{C}[0,1] : f(0)=f(1)=0\}$ but the neither $f$ nor $g$ is in $\mathcal{I}$.    I have two questions:   I see that $0$ does not play any role in the question $\mathcal{I}=\{f\in \mathcal{C}[0,1] : f(0)=0\}$ I mean I would have same case if i replace $0$ by any real number.  So, I would like to say that $$\mathcal{I}=\{f\in \mathcal{C}[0,1] : f(r)=0\}$$  is a maximal ideal in the ring $\mathcal{C}[0,1]$ of all continuous real valued functions.  And one more thing I would claim is that      If the collection $\mathcal{I}$ is such that all elements of $\mathcal{I}$ has more than $1$ common zero then $\mathcal{I}$ is not a maximal ideal and not even a prime ideal..   I would like to learn more about this kind of ideals in $\mathcal{C}[0,1]$.  I would be thankful if some one can assure that what  have done is sufficient to conlcude what i have concluded and I would be thankful if some one can suggest some material to read regarding this.  Thank you


Does ubuntu require antivirus? If yes then please tell me what's the difference between windows virus and ubuntu virus?

I thought that there was no need to scan for viruses either in Ubuntu or any Linux distros until I found virus scanner packages clamtk and klamav in Ubuntu software center yesterday.  This leads to the following questions:   How do viruses differ between Linux and Windows? How do the strategies for protection differ between Linux and Windows? Should a virus scanner package be installed on my system? If so, which would be a better option?


Aw, don't be silly. Well, I think so. So we'll say, "There're books in the library." We can also say, "We know there're not lots of foods or drinks in the library, but only books."

Q: "Do you have any juice?"   A: "Yes, there's some in the fridge."   Sounds perfectly fine to me, but:     Q: "Do you have any towels?"   A: "Yes, there's some in the closet."   Does not.  I asked for towels - plural - so wouldn't "Yes, there're some in the closet," in which there are is turned into a contraction be the correct way to say it?  Spellcheck, however, doesn't like "there're", and I think I'm the only person I've ever heard use the word "there're".  Even folks who I know say "there are" shorten it to "there's" when possible.  Am I saying it wrong, or are both forms acceptable?


I want to remove the Windows 10 from my laptop and switch to Ubuntu. But I am not sure which Ubuntu version that support the laptop.  The laptop is HP 14-bw001au.  Thank you.

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


I have a question regarding word usage when using "trio" in a sentence.   Here's an example sentence:     The trio tries to find the way but appear to be lost.   Should "tries" be in the third person, or should it remain "try"? The example will apply to other cases in which another word instead of "try" was used, but an answer to this will help clarify this for me in the future.

According to , a trio is defined as "any group of three persons or things".  trio noun, plural trios. any group of three persons or things.  Trio is a singular noun that refers to a group of people. Is this singular word ambiguous with its plural meaning? This is the sentence that sparked this question:  Without idle chitchat to distract them, the trio was reminded of their missing friend.  The fragment uses the word "them" to refer to the three people. However, should "was" be "were", or is it fine as it is? Since trio means a group of things, yet the word itself is not automatically plural, I find it disconcerting to switch from plural to singular pronouns.


I've been reading up on how to filter out spam from Google Analytics. In this case, I'm trying to filter out the spam that shows up under referrals.  In the Filter Pattern field of Analytics, I have the following:  semalt\.com|buttons-for-website\.com|rank-checker\.online|monetizationking\.net|site-auditor\.online   Yet it makes no difference to my Analytics. I've also clicked the verify link but all I get back is:     This filter would not have changed your data. Either the filter   configuration is incorrect, or the set of sampled data is too small.   Am I doing something wrong?

Last months I have lots of referrer spammers in my GA statistics. Their count is ~10x higher than count of legit visitors (my site is not very popular yet). I've turned on an option to hide known spammers in GA settings, but it didn't help at all. It seems these spammers are using scripts to spam directly to GA (i.e. they are not logged in my IIS).  Is there anything I can do to stop these spammers?    UPD 10 months later, and they started spamming using fake target page names... and Google is still doing nothing about it.


I just picked up the spell  (XGtE, p. 164) and had a chance to try it out last session. The wording has caused some confusion and a disagreement between myself and my DM. The spell states:  When a creature moves into the spell's area for the first time on a turn or starts its turn there, that creature must succeed on a Constitution saving throw or take 4d10 radiant damage [...]  We were fighting multiple vampires. I cast Sickening Radiance on the enemy group. DM immediately rules that due to the language of the spell, they are not affected by it, since they "haven't started their turn in it" and they "didn't move into it". Okay, fair enough. They'll start their turn there, so I'm not concerned. They start their turn within it and are dealt the damage. They then, logically, move out of the spell, but stand five feet out of it. Their turn ends, and my turn begins. I cast Eldritch Blast twice along with the Invocation Repelling Blast to push two of them 10 feet, which shoves them into the spell's effect area. The DM moves onto the next person; I gently remind him that they need to make Constitution saves for Sickening Radiance. He refuses, stating that the language of Sickening Radiance uses "moves", not "pushed", and therefore is only triggered by the target using their movement, not just any movement into it. I obviously disagree, and argue that it just says "moves into", which they did, as a result of my Eldritch Blast. Obviously DM fiat and all that, so if he says it doesn't work, it doesn't work. But I'm still curious about a rules based answer to this, as it seems like a very strict (and likely incorrect) reading. Does Sickening Radiance require the target to use their movement (i.e. not be forcibly moved) for the spell to deal damage?

The description of the moonbeam spell (PHB pg. 261) says:  When a creature enters the spell's area for the first time on a turn or starts its turn there, it is engulfed in ghostly flames that cause searing pain... On each of your turns after you cast this spell, you can use an action to move the beam 60 feet in any direction.  We read this to mean a creature takes damage from moonbeam when any of the following conditions are met:  It begins its turn inside the moonbeam It enters the moonbeam on its turn The creature finds itself inside the beam on another character's turn, no matter how it got there  The creature will not take damage in the following instances:  A creature moves from one part of the beam to another (obviously it had to take damage, but it won't take more damage) A creature is in the beam after having been inside the beam already on that turn.  Following these assumptions, our druid cast a moonbeam and did damage to two enemies, Bob and Frank. On their turn, they took damage again, killing Bob. Frank left the beam. On the druid's next turn, she moved the beam in a circular motion, not exceeding 60 total feet of movement, and in the process the beam came in contact with a dozen enemies and ended on Frank. All dozen enemies received damage, as they were inside the beam at some point during the turn. On Frank's next turn, he again took damage for the fourth time and died. On each of the druid's turns, she moved the moonbeam around like this until the fight ended (it did not exceed the time limit and she made all concentration checks). Is this a legitimate use of moonbeam? It seems awfully powerful for a level 2 spell.


I was wondering if there is a way to get the computer name in Java? I have seen several answers that feature java.net.InetAddress. However I was wondering if there is a way that does not use the network?  (As a side question, is the computer name only a network thing anyway, so therefore has to be done this way??)

Is it possible to get the name of the currently logged in user (Windows/Unix) and the hostname of the machine?  I assume it's just a property of some static environment class.  I've found this for the user name  com.sun.security.auth.module.NTSystem NTSystem = new         com.sun.security.auth.module.NTSystem(); System.out.println(NTSystem.getName());   and this for the machine name:  import java.net.InetAddress; ... String computerName; ... try {     computerName = InetAddress.getLocalHost().getHostName(); }  catch(Exception ex) {     ... }   Is the first one just for Windows?  And what will the second one do, if you don't have a hostname set?


How do I get the position, rather than the value, of the highest one bit in integer? I know I can get the value like this:  // Prints 8; in 1101, the highest bit is the one denoting 8 int f = 13; System.out.println("Highest: " + Integer.highestOneBit(f));   However, I'd like to get position of the highest one bit - in this case, it would be 4 (since 1000 in binary == 8, the highest one bit is the fourth one).

This is probably pretty basic, but to save me an hour or so of grief can anyone tell me how you can work out the number of bits required to represent a given positive integer in Java?  e.g. I get a decimal 11, (1011). I need to get the answer, 4.  I figured if I could work out how to set all the bits other than the most significant bit to 0, and then >>> it, I'd get my answer. But... I can't.


I have been trying to put an image in blender so I can make a 3d model of it but it does not seem to show up. Any good tutorials for blender 2.71 to show me how it is done? Thanks

How do I put a backdrop behind the model that I am creating so that I can compare the picture to the model while editing?


I done my assignment and upload it but in the public test I failed because of this java.lang.NullPointerException error. I searched in the Internet but I don´t know how to use it in my code.  testFilmStartenStoppen(PublicTests) java.lang.NullPointerException  Public Test: public void testFilmStartenStoppen(){         assertTrue(!k.filmStarten(f));         assertTrue(!k.filmStoppen());         Kunde k2 = new Kunde("Little", "Timmy", 9, "Koblenz", Zahlungsmittel.GUTSCHEIN);         Kunde k3 = new Kunde("Big", "Tommy", 200, "Koblenz", Zahlungsmittel.PAYPAL);         k.setPortal(b);         k2.setPortal(b);         k3.setPortal(b);         assertTrue(!k.filmStoppen());         assertTrue(!k.filmStarten(null));         int kap = b.getServer().getKapazitaet();         assertTrue(k.filmStarten(f));         assertEquals(kap-1, b.getServer().getKapazitaet());         assertTrue(k.isSchautFilm());                  kap = b.getServer().getKapazitaet();         assertTrue(k.filmStoppen());         assertEquals(kap+1, b.getServer().getKapazitaet());         assertTrue(!k2.filmStarten(f));         k3.filmStarten(f);         assertTrue(!k.filmStarten(f));         k3.filmStoppen();         assertTrue(k.filmStarten(f));              }  My Code: public boolean filmStarten(Film film) {         try {             boolean result = false;             Film filmExistiert = this.filmSuchen(film.getTitel());             if (null != filmExistiert && this.getPortal().getServer().getKapazitaet() > 0                     && this.getAlter() >= film.getFsk()) {                 this.getPortal().getServer().setKapazitaet(this.getPortal().getServer().getKapazitaet() - 1);                 this.schautFilm = true;                 result = true;             }             return result;         } catch (Exception e) {             return false;         }     }      public boolean filmStoppen() {         try {             boolean result = false;             if (this.isSchautFilm()) {                 this.getPortal().getServer().setKapazitaet(this.getPortal().getServer().getKapazitaet() + 1);                 this.schautFilm = false;                 result = true;             }              return result;         } catch (Exception e) {             return false;         }     }  My question How can I solve this problem?

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


Question: Which of the following intervals contains integers satisfying the following three congruences: $x\equiv 2\pmod 5, x\equiv 3\pmod 7$ and $x\equiv 4\pmod {11}$, (i) $[401,600]$, (ii) $[601,800]$, (iii) $[801,1000]$, and (iv) $[1001,1200]$    After solving I have found $x=2292\equiv 367\pmod {385}$. But this does not belong to any of the above option.  How can I find this solution?

Which of the following intervals contains an integer satisfying following three congruences   $$x=2\pmod5\\ x=3\pmod7\\ x=4\pmod{11}$$   $a) [401,600] \\ b)[601, 800] \\ c)[801,1000] \\ d)[1001,1200]$   (CSIR NET 2015 Dec)  I tried this question and I got answer but it is not in the option. I applied Chinese remainder theorem.  $$x=2\pmod5\\ x=3\pmod7\\ x=4\pmod {11}$$  $$N_1=7\times11=77\\ N_2=5\times11=55\\ N_3=7\times5=35$$  $77x=1\pmod5\implies b_1=3\\ 55x=1\pmod7\implies b_2=6\\ 35x=1\pmod {11} \implies b_3=6$  then, $x=2\times77\times3+3\times55\times6+6\times35\times4=2292$  This answer is not in the option.  If my work is wrong please correct it.


Iam trying to pass model of data from mvc controller to page from a ajax post call. I get data successfullt. But the dates contain in the model are converted like "/Date(1455647400000)/". How can i convert it into "wed feb 03 2013". please help me.   My code:  public JsonResult getHeaderData(string code) {     if (code != "")     {         var userData = (IdentityModel)(Session["DATA"]);         decimal doc_no = Convert.ToDecimal(code);         var data = _transactionHeaderManager.GetHeaderDataByDocNo(userData.CompanyCode, userData.BranchCode, "ASTS", doc_no);         var resultData = Mapper.Map<AssetTransactionHeaderModel, AssetTransactionHeaderViewModel>(data);         return Json(resultData, JsonRequestBehavior.AllowGet);      }     else     {         return null;     } }

I have a controller action that effectively simply returns a JsonResult of my model. So, in my method I have something like the following:  return new JsonResult(myModel);   This works well, except for one problem. There is a date property in the model and this appears to be returned in the Json result like so:  "\/Date(1239018869048)\/"   How should I be dealing with dates so they are returned in the format I require? Or how do I handle this format above in script?


\begin{array}{rcl}  f: R^3 & \to & R \\  (x,y,z) & \to & x + y + z \\  f(x,y,z) & = & x + y + z  \end{array}  I inserted this code to my latex but it won't compile. It gives me following errors:  ! Missing $ inserted.$ \begin{array}{rcl} ! Missing $ inserted.$ ...z \ f(x,y,z) & = & x + y + z \end{array}  I am not sure what I did wrong...

Been trying to this line to parse for a good 20mins, but all attempts have failed:  \beta = $-$0.84, t = $-$2.09, P = 0.04   Could anyone tell me why I'm getting a Missing $ inserted error here?


In Update Manager I try to update the list of packages and I get a window titled synaptic with the following output    Failed to fetch   404  Not Found [IP: 2001:67c:1360:8c01::18 80]  (many more lines like this)  Some index files failed to download. They have been ignored, or old ones used instead.    How do I fix this?  Please answer with complete step by step instructions. Thanks.

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


A rather stupid question, why can we see the moon when it is between the Earth and the Sun?

I know this sounds like (and probably is) a stupid question, but I can't figure it out.  As far as I know, the crescent shape of the moon is when the moon is on the sunny side of the Earth, but that wouldn't explain how it can be seen from the night.  Horrible, not-to-scale and probably completely wrong diagram of what I think :    How is it that we can see clear to the other side of the Earth?


Give an example of a non-linear mapping from $\mathbb R$ onto $\mathbb R$ whose graph is closed although it is not continuous.

I tried looking up a question regarding graphs of continuous functions on this site, but all the ones I found consider functions from $\mathbb{R}$ into $\mathbb{R}$. I have been pondering the following question: given a general topological spaces $X, Y$, and a function $f: X\to Y$, when does $Graph(f)$ closed in $X\times Y$ imply that $f$ is continuous. By the closed graph theorem, this is true whenever $X$ and $Y$ are both Banach spaces.   Also, it is fairly easy to prove that whenever $Y$ is a Hausdorff space and $f$ is continuous, then $Graph(f)$ is closed, but I do not think that the converse is true, so I am trying to find an example where $X$ is some topological space, $Y$ a Hausdorff space, $f: X\to Y$ a function with a closed graph in $X\times Y$, but who fails to be continuous. As of yet I have not been able to find such a counterexample, partially because I have no clue where to look for such a counterexample. I would really appreciate getting some directions to go in.


I am getting a wrong result when I perform the following operation  $n1 = 178.200; $n2 = 89.100; $n3 = 178.199; $n4 = 89.101; $n5 = 170.999; $grandTotal = $n1+$n2+$n3+$n4+$n5; $discount = 700.000; $netTotal = $grandTotal - $discount; echo "Grand Total:".$grandTotal."
"; echo "Discount:".$discount."
"; echo "Net Total:".$netTotal."
";    Output:  Grand Total: 705.599 Discount: 700.000 Net Total: 5.5989999999999   But 705.599-700.000 = 5.599 right ?   Why Im getting this 5.5989999999999 ?

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


In my attempt to set up a dual boot system, by installing Ubuntu 14.04 onto my system with Windows 7, I have encountered a pretty stubborn problem.  I have loaded ubuntu into a bootable USB device.  When installing Ubuntu, whether through "try ubuntu w/o installing" or the other "install Ubuntu" option, Ubuntu never presents the "install alongside windows option".  The only two options that I have are the 1. erase all data and install ubuntu on drive and 2. do other stuff (display partitions)    Looking at posts by folks who have encountered this issue in the past, I have attempted some of the various suggested solutions.. without avail.  fixparts remove dmraid   I have a boot repair log up:   Any help would be greatly appreciated!

Whenever I startup from the LinuxLive USB, and try to install Ubuntu 12.04, it only gives me two options instead of the usual 3 or 4. My options are "Replace Windows 7 with Ubuntu" and "Something Else". Whenever I go into "Something else", it looks extremely confusing. How do I install it side-by-side while using the "Something else" section? These are my partitions.   /dev/sda /dev/sda1 ntfs (104Mb, System Required Partition) /dev/sda2 ntfs (1000097Mb, Windows 7 Partition)   Or should I try reinstalling my installer on a CD rather than USB and maybe then it will have the "Install alongside" function?


Problem statement (and solution):     Let p be a prime satisfying $p \equiv 3 \pmod{4}$. Show that if the equation $x^2\equiv a \pmod{p}$ is soluble, then its solution is given by (1):   $$x \equiv \pm a^{\frac{p+1}{4}} \pmod{p}$$    Solution: $x^2 \equiv a \pmod{p}$ implies that $(a\mid p) = 1$ So by Euler's criterion: $a^{\frac{p-1}{2}} \equiv 1 \pmod{p}$  if (1) holds, we have: $x^2 \equiv a^{\frac{p+1}{2}} \equiv a^{\frac{p+1}{2}} * a^{\frac{p-1}{2}} \equiv a^p \pmod{p}$  By Fermat's Little Theorem, $a^p \equiv a \pmod{p}$  This quite obviously also works in the other direction. My only real question is, why does the problem statement limit the space to primes congruent to 3 mod 4? Why would this exact proof not work for primes congruent 1 mod 4? What am I missing?

Let $p$ be a prime satisfying $p\equiv 3 \mod 4$. Let $a$ be a quadratic residue modulo $p$. Prove that the number $$b\equiv a^\frac{p+1}{4} \mod p$$ has the property that $b^2\equiv a \mod p$. (Hint: Write $\frac{p+1}{2}$ as $1+\frac{p-1}{2}$.) This gives an easy way to take square roots modulo $p$ for primes that are congruent to $3$ modulo $p$. \textit{Hint:} Write $\frac{p+1}{2}$ as $1+\frac{p-1}{2}$ and use Exercise $3.36$.) This gives an easy way to take square roots modulo $p$ for primes that are congruent to $3$ modulo $p$.  I assume that the proof comes directly from the proof of quadratic residues but I am not sure how.


I'd like to watch youtube videos with a small video down in the corner without a lot of wasted space on the screen such as title bars, address bar, bookmarks bar, scroll bar, etc.

I am looking for an application or a GNOME Shell extension which I can use to easily and non-intrusively monitor other windows without having to have them on top in any way.  So I would like it to have the following features:   The ability to show window previews of windows without having them on top and even showing minimized windows Allow showing the window preview in any corners of the screen Allow one with ease to view what is behind the window preview on screen and click on what is behind it Allow windows from different workspaces to be accessible Allow the resizing of the window preview Allow the switching on and off of the window preview with ease Allow the viewing of workspaces in the preview   I am running Ubuntu GNOME 17.04 with GNOME 3.24.1, is there such an extension?  This would be really useful for when I need to be monitoring a system application or I want to watch a film or a video call while doing work or other stuff and don't want to either have two windows taking up either half of the screen or to have to keep switching between them.


I've been stuck on the following problem for several days: Let $(M,d)$ be an arbitrary metric space and $S, T$ be subsets of $M$.  If $S$ is closed and $T$ is compact, then $S \cap T$ is compact.  I know that if $T$ is compact, $T$ is  closed and bounded. That would imply that $S \cap T$ is also closed and bounded since $(S \cap T) \subseteq T$. Also since $S$ is closed, $S$ contains all its accumulation points.  Other than writing down the definitions, I really don't know how to proceed. Could someone give me a hint?

I am going through Rudin's Principles of Mathematical Analysis in preparation for the masters exam, and I am seeking clarification on a corollary.  Theorem 2.34 states that compact sets in metric spaces are closed. Theorem 2.35 states that closed subsets of compact spaces are compact. As a corollary, Rudin then states that if $L$ is closed and $K$ is compact, then their intersection $L \cap K$ is compact, citing 2.34 and 2.24(b) (intersections of closed sets are closed) to argue that $L \cap K$ is closed, and then using 2.35 to show that $L \cap K$ is compact as a closed subset of a compact set.  Am I correct in believing that this corollary holds for metric spaces, and not in general topological spaces?


While working on , the joys of TDD helped me stumble upon a really strange (at least as i occurs to me) behaviour exposed in the javascript engines.  No matter if entered into the console or performed inside a script, this is what happens:  -1 + 0.85     --> -0.85               ✓   -1 + 1        --> 0                   ✓    -1 + 1 + -.15 --> 0.15                ✓ -1 + 1.15     --> 0.1499999999999999  ?!?   This is tested and reproduced exactly under following Browsers / OS's:   FF 24.0 (Debian 3.10)  Chrome 30.0.1599.114 (Debian 3.10)  Chrome 30.0.1599.101m (Win7SP1) Internet Explorer 10.0.9200.16721 (Win7SP1)   As this is consistent throughout different vendors, i assume there must be a specific reason for this, so:   What is the reason for this? What is the best practice to circumvent this behaviour, as it poses a problem for exact calculations with JS     Update: Best lay-comprehensible explanation incl. answers and workarounds for multiple programming languages so far found at   (thanx @RocketHazmat)


I need to prove that $P(A \cup B) = P(A) + P(B) - P(A \cap B)$.   How do you prove this with the help of axioms?  Also, can anyone suggest books where I could look through proofs of axioms and proofs of properties derived from axioms.

I'm taking my first course in Probability and one of my homework problems is to prove that for any two sets:  $$P(A \cup B) = P(A) + P(B) - P(A \cap B) $$  Note that the function $P$ is the probability of an event happening.  From the third axiom, we are given that for any two disjoint sets, that is $ A \cap B = \emptyset$:  $$P(A \cup B) = P(A) + P(B)$$    My thought process follows from this third axiom, but I run into a problem near the end:  Since $A$ and $B$ are disjoint sets, $P(A)=P(A-B)$ and $P(B)=P(B-A)$, so  $$P(A \cup B) = P(A) + P(B)=P(A-B)+P(B-A)$$  From this, it appears that we are essentially taking the symmetric difference of A and B.  This, to me, seems to be equivalent to:  $$P(A-B)+P(B-A)=P(A)+P(B)-P(A \cap B)$$  Hence, by my logic:  $$P(A \cup B) = P(A)+P(B)-P(A \cap B)$$  Which, in essence, doesn't care whether two sets are disjoint or not as we are subtracting the intersection of them.  If the sets are disjoint, then the intersection is merely null.  If they intersect, then we are removing the "extra pieces".  I feel like this is inadequate proof despite my ability to convince myself that it is true..  Where, if anywhere, did I go wrong?  Thanks!


I'm trying to determine whether this statement is true or false. However I only understand that every finite extension of a finite field is separable from another solution. ()  So what difference is finite or not with regards to the finite extension being separable or not?  Thank you

My class notes has as theorem (without proof): "Let $K/F$ be finite field extension, with $K=F(\alpha_1,\ldots,\alpha_n)$ and $\alpha_k$ is separable for all $k$. Then $K/F$ is separable".  My question is: in either finite field, or field characteristic $0$, will the $\alpha_k$ always be separable? (by "$\alpha_k$ separable" I mean that its minimal polynomial is separable). Also, could somebody give me an example for which an $\alpha_k$ is not separable?


I can generate a list of accordions after an AJAX call in this way:  data.items.forEach(function(item,index) {                 if(item.desciption != "") {                     $('#accordionList').append(                         templateAccordion(item, index)                 );           } });   where templateAccordion is:  var templateAccordion = function(item, index) {         return '
' +         '
' +         '
'+           '<button class="btn btn-link collapsed">'+             item.desciption +            '</button>'+         '
'+       '
'+        '
'+         '
' +          '
'+       '
'+     '
'     }   Problem:  I need to call another service when I click over the header of each accordion to get other data about that element. To do this, I thought 2 possible ways.   The first one is the onclick="" function on the header of the element (like in my example). But this solution doesn't work because I get a Uncaught ReferenceError: test is not defined (and the function exists in my javascript).   The second is trigger the click function using the id of the header. But it's dynamic as you can see. So I don't have it because it could be 1,2,3 and so on.   I can't loop over the whole list and try to get the correct id. It is unthinkable.   Is there any onther way? Maybe just understand why it gets me Uncaught ReferenceError: test is not defined?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I have a question about fermi level (chemical potential). It is stated that the fermi level is the thermodynamic work required to add one electron to the body of a material. How is it possible that, regardles of temperature, fermi level is in the band gap? Since those energies aren't allowed, how can they be the work required to add one electron to the body of a semiconductor. I now there are other definitons, but how is this problem explained?

What does it mean that the  for some semiconductors lie in the band gap?  Is Fermi level definition different from what is know as usual?  We define the Fermi level as the highest level of energy which is occupied by electrons.  Then what is missing here?


I search the Laurent series of $\sin(\frac{z}{z+1})$ in the point $z_0=-1$. What I did is write the taylor expansion   $$\sin\Big(\frac{z}{z+1}\Big)=\sum_{n=0}^\infty(-1)^n\frac{\Big(\frac{z}{z+1}\Big)^{2n+1}}{(2n+1)!}$$  But this can't be right, since I didn't take $z_0$ into account. How can I do the Laurent expansion in this case?

I'm trying to find the Laurent Series for $\sin\left(\frac{z}{1+z}\right)$ centered around $z = -1.$ It seems to me that I should be considering the typical power series expansion of $\sin$, i.e.  $$\sin(w) = \sum_{k = 0}^{\infty} (-1)^k \frac{w^{2k+1}}{(2k+1)!}.$$  However, when I perform this with our current function, I see that  $$\sin\left(\frac{z}{1+z}\right) = \sum_{k = 0}^{\infty} (-1)^k \frac{z^{2k+1}}{(1+z)^{2k+1}(2k+1)!}.$$  I am not entirely sure what to do with $z^{k+1}.$ Are there some other things that I should be doing with this series to account for the singularity of $\frac{z}{1+z}$ at $z = -1$?


I want to copy the bones on one side symmetrically.  I selected the bone to be symmetrized and armature-> symmetrize, but nothing happened.  How can I symmetrize the bones?

I need to mirror the half part of the rigging of my character, I remember it was something with the scale or rotation.. does anyone know which was the right solution step-to-step?