How to invoke generic Action?
How do I use reflection to call a generic method?
The question is from Axler's "Linear Algebra Done Right", which I'm using for self-study.  We are given a linear operator $T$ over a finite dimensional vector space $V$. We have to show that $T$ is a scalar multiple of the identity iff $\forall S \in {\cal L}(V), TS = ST$. Here, ${\cal L}(V)$ denotes the set of all linear operators over $V$.  One direction is easy to prove. If $T$ is a scalar multiple of the identity, then there exists a scalar $a$ such that $Tv = av$, $\forall v \in V$. Hence, given an arbitrary vector $w$, $$TS(w) = T(Sw) = a(Sw) = S(aw) = S(Tw) = ST(w)$$ where the third equality is possible because $S$ is a linear operator. Then, it follows that $TS = ST$, as required.  I am, however, at a loss as to how to tackle the other direction. I thought that a proof by contradiction,  ultimately constructing a linear operator $S$ for which $TS \neq ST$, might be the way to go, but haven't made much progress.   Thanks in advance! I'm trying to figure out the best way to model the sphere-spiral here:    Is it possible to make this shape directly? Or do you have to make it as a cylinder and wrap it to a sphere? The use of nominative "whom" (as in “persons whom it is foreseeable are likely to...”) Please make the multiple comment timer less annoying (non-resetting etc.) As a little feature to prevent comment spam, you can only enter one comment every 15 seconds. That's a very reasonable limitation, since you very rarely have a good reason to write comments that quickly. I've only seen it twice at all, I think, but both times it was extremely annoying.     Only 1 comment allowed per 15 seconds; timer reset.   The reason is that every time you hit the limit, the 15 seconds begin anew. You have no indicator that tells you when you are allowed to comment again, and if you hit enter after just 14 seconds, you're back to zero. Yesterday, I went through four cycles of not quite 15 seconds, counting in my head, before I got a myself a coffee and tried again afterwards.  I suggest that you do one or more of the following (in decreasing order):   Make the counter non-restarting Add a visible countdown Make it clearly visible that you can't comment right now You can actually increase the waiting time, if it is clearly visible and there is no unnerving invisible countdown. Actually, just remove all comment fields after one comment, and tell the user to reload the page. Just please don't have UI elements that look like they would work, but feel like they are trolling you. Find the value of : $\cos x \cos 2x...\cos 999x$ given that $x=\frac {2\pi}{1999}$ story on forest timescale I'm looking for the title of a short story by Ursula Le Guin about a scientist (?) who is given a drug that slows the timescale of his perception enormously, so that he can perceive that an alien (?) forest is actually behaving as a sentient being, reacting to current events, but at an enormously slow (from a normal human point of view) timescale. It might be in , but I don't remember the title (and it doesn't jump out at me from the list of titles) and don't have access to that collection right now. It is not &quot;The Word for World is Forest&quot;, nor &quot;Direction of the Road&quot; (from ), nor &quot;Vaster than Empires and More Slow&quot;, the latter two of which look at similar plant perception/time-scale issues. Update: it turns out that the description was right, but I had most of the details wrong: not Le Guin, not alien, not a scientist ... I'm trying to prove that $(ma, mb) = $|$m$|$(a, b)$ , where $(ma, mb)$ is the greatest common divisor between $ma$ and $mb$. My thoughts: If $(ma, mb) = d$ , then $d$|$ma$ and $d$|$mb$ → $d$|$max + mby$ → $d$|$m(ax+by)$. This implies that $d$|$m$ or $d$|$(ax+by)$. This is the same as  $d$|$m$ or $d$|$a$ and $d$|$b$, so $d$|$m$ or $d$|$(a,b)$. This is the same as $d$|$m|$ or $d|(a,b)$, so $d$|$|m|(a,b)$. I don't know what to do. Why is there "Germany National Team", not "German National Team"? Why is the team from Germany called "Germany National Team", not "German National Team"? On official Internet sites, it is the same for every official national team; Germany National, France National, Poland National, Russia National etc. etc. What truthfully bothers me is why not German, French, Polish, Russian etc? Prove that $a^2 + b^2 \geq 8$ if $ x^4 + ax^3 + 2x^2 + bx + 1 = 0 $ has at least one real root. If it is known that the equation $$ x^4 + ax^3 + 2x^2 + bx + 1 = 0 $$ has a (real) root, prove the inequality $$ a^2 + b^2 \geq 8. $$  I am stuck on this problem, though, it is a very easy problem for my math teacher. Anyway, I can't figure out. The various modern revolutions in physics, in psychology, in politics, even in literary style, have not escaped his intelligent notice, but they can scarcely be said to have influenced him deeply.    Could you please explain the following?  They can scarcely be said to have influenced him deeply.  Or, I can not understand such a structure like the following:  In contrast, prices set by a central planner are necessarily arbitrary, since there is no standard against which they can be said to be correct or incorrect. d'oh! What does Minecraft's scary music mean? Apparently it means there is a dungeon around but I can never find any?  If it does mean dungeons how far away will it trigger? Why do some Unicode text messages crash the iPhone OS? Amy: What day is it today?    Tom: It's Monday. Hmm... I like Monday.   Amy: What do you have today?   Tom: We have math, science and art.What about you?   Amy: We have English and P.E. What do you have tomorrow?    Tom: We have art and P.E.tomorrow.    Amy: Oh, great.      I can understand that "What about you" means "What do you have today?"  But I wonder whether "What about you" is an elliptical sentence. If it is, what is the full sentence? If it isn't, how to parse this structure? I'm printing a tradeshow flyer and was wondering what type of paper I should print it on. I don't want anything glossy so I'm trying to decide on the following:   100# text weight matte 80# cover 80# matte   What is the difference between the types above? And how can I make a decision? I want to give a client access to my server, but I want to limit those users to their home directories. I will bind-mount in any files I want them to be able to see.  I've created a user called bob and added him to a new group called sftponly. They have a home directory at /home/bob. I've changed their shell to /bin/false to stop SSH logins. Here is their /etc/passwd line:  bob:x:1001:1002::/home/bob:/bin/false   I've also changed the /etc/ssh/sshd_config to include the following:  Match Group sftponly         ChrootDirectory /home/%u         ForceCommand internal-sftp         AllowTcpForwarding no   When I try to log in as them, here's what I see   $ sftp bob@server bob@server's password:  Write failed: Broken pipe Couldn't read packet: Connection reset by peer   If I comment out the ChrootDirectory line I can SFTP in but then they have free rein over the server. I have found that ChrootDirectory /home works, but it still gives them access to any home directory. I have explicitly tried ChrootDirectory /home/bob but that doesn't work either.  What am I doing wrong? How can I limit bob to /home/bob/?  ----EDIT-----  Okay so I just had a look at /var/log/auth.log and saw this:  May  9 14:45:48 nj sshd[5074]: pam_unix(sshd:session): session opened for user bob by (uid=0) May  9 14:45:48 nj sshd[5091]: fatal: bad ownership or modes for chroot directory component "/home/bob/" May  9 14:45:48 nj sshd[5074]: pam_unix(sshd:session): session closed for user bob   I'm not entirely sure what's going on there,  but it suggests something is wrong with the user directory. Here is the ls -h /home output:  drwxr-xr-x 26 oli      oli      4096 2012-01-19 17:19 oli drwxr-xr-x  3 bob      bob      4096 2012-05-09 14:11 bob The result set has no current row while using JDBC I am using the following code in selenium, but I am not able to retrieve data from database. I am getting the errors "The result set has no current row"  My code is   public class Auto {      public static void main(String[] args) throws InterruptedException, SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException     {           Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");         System.out.println("Driver loaded");           Connection con=DriverManager.getConnection("jdbc:sqlserver://192.168.*****\\SQLEXPRESS/*****_DW/EPS:****;user=******;password=******; ");          System.out.println("Driver loadedd");       java.sql.Statement stmt= con.createStatement();     ResultSet rs=stmt.executeQuery("select * from [*****_DW].[dbo].dim_grantee ");      System.out.println("Query executed");      while (rs.next());     {         String Name=rs.getString("NAME");          System.out.println("Name is");     }   } I have the following sequences $(a_n)$, $(b_n)=(a_{2n})$, and $(c_n) = (a_{2n-1})$.  I have to show that:   if $(b_n)$ and $(c_n)$ both convergence to $a$, then $(a_n)$ also converges to $a$; if $(a_n)$ converges then $(b_n)$ and $(c_n)$ also converge; there exist $(a_n)$ not converging but with $(b_n)$ and $(c_n)$ converging.   I am not sure how to solve this since I only know that $(b_n)$ > $(c_n)$ > $(a_n)$ on the terms how the sequences are defined. Titles of articles I'm about to cite contain upper case letters and when using BibTeX it converts them to lower case ones. This happens only in the title and only the first letter conserves its case. For example, when I cite an article about HF, the reader won't know if it is about Hafnium (Hf) or fluorine acid (HF).  I know that I can fix it manually in the .bbl file but I would like to avoid it, or fix it automatically. Convergence of $\int_0^\infty \sin(t)/t^\gamma \mathrm{d}t$ For what values of $\gamma\geq 0$ does the improper integral $$\int_0^\infty \frac{\sin(t)}{t^\gamma} \mathrm{d}t$$ converge?   In order to avoid two "critical points" $0$ and $+\infty$ I've thought that it would be easier to test the convergence of the sum (is this coherent?): $$ \int_0^1 \frac{\sin(t)}{t^\gamma}\mathrm{d}t + \int_1^\infty \frac{\sin(t)}{t^\gamma}\mathrm{d}t. $$ For the second integral, it converges if $\gamma &gt; 1$ (comparision) and also converges if $0 &lt;\gamma \leq 1$. I'm stuck on proving the last part and the fact that the first integral converges for $\gamma &lt; 2$. Any help would be appreciated. Thanks in advance.  PD: I've checked the answers for  but I would not like to solve this integral using $(n\pi,(n+1)\pi)$ intervals. How do I reset proxy in terminal to automatic if not connected via proxy I tried to reset proxy of the terminal by some commands but it doesn't happen and automatically switches back to this proxy 172.16.0.16 (which apparently was my college proxy).   I checked in my system settings.I don't understand why this is recurring. Please be comprehensive.Also I further would like to know how to bypass proxy server since I couldn't access any of the ubuntu repositories as they were blocked in my college's proxy settings as is Ubuntu's homepage.  Thanks for your time.    For sudo ls /etc/apt/apt.conf.d/        It displays a different set of options where proxy is not listed.I am on 12.10,if this should help any.I put a snap of the terminal after the above command has been entered.