Negation operator logic not making sense
What do the plus and minus signs mean in Objective-C next to a method?
Compile error: package javax.servlet does not exist How to select lines between two marker patterns which may occur multiple times with awk/sed if $x+2y+z=4$ and $x,y,z$ are real number. then find maximum value of $xy+yz+zx$  putting $x+z=4-2z$ in $y(x+z)+zx = y(4-2z)+zx = 4y-2yz+zx$  i wan,t be able to  go further,could some help me with this To prove $ \tan(A) + 2 \tan(2A) +4\tan4A + 8 \cot8A =\cot(A) $ lsusb relevant output Bus 001 Device 006: ID 0bda:8812 Realtek Semiconductor Corp. RTL8812AU 802.11a/b/g/n/ac WLAN Adapter  Upon plugging the device it is recognized by lsusb, however when I go to wireless settings no adapter is recognized. The driver is installed (by going to software and updates -> addition drivers and selecting the open source driver). I have a file with the lines like below.  title1:A1 title2:A2 title3:A3 title4:A4 title5:A5  title1:B1 title2:B2 title3:B3 title4:B4 title5:B5  title1:C1 title2:C2 title3:C3 title4:C4 title5:C5  title1:D1 title2:D2 title3:D3 title4:D4 title5:D5  How can I achieve this?   title1    title2     title3    title4 A1         A2         A3         A4 B1         B2         B3         B4 C1         C2         C3         C4 D1         D2         D3         D4 If I use the starting wealth rolls of my class, do I keep any remaining money left over? If I use the starting wealth rolls of my class, do I keep any remaining money left over after I buy equipment?  In D&amp;D 5e you can roll the 4d4 &times; 10 to determine starting gold, forgoing any equipment your class and background  gets.  This is not up for question.  What is up for question is whether or not the PC keeps any remaining gold that they don't spend on equipment.   As far as I have been able to tell, this is not explicitly stated in the PHB nor in the Basic Rules documents. Can you cast a spell at a higher level, even if it doesn't have an "At higher levels" entry? Many spells have "At higher levels" that provides for more targets or more damage.  For example Magic Missile can be cast as a second level spell and shoot 4 missiles instead of it's 3 as a first level spell.  Can a spell without that verbiage, such as Firestorm be cast in higher level slots for the same effect as the lower level spell? How do I decompile a .NET EXE into readable C# source code? I wrote a C# application for a client a couple of years ago, but I no longer have the source code.  All I have is the EXE that I deployed on the client's PC.  Is there a way I can generate C# source code from the EXE? What is the difference between topological and metric spaces? What is the difference between a topological and a metric space? Passing Javascript variable to Can I use grep matches to execute command? I need to upgrade php from 5.3 to 5.4. I've installed it with rpm. I want clean install: delete all 5.3 packages, and install all necessary 5.4. Here is the command to see all installed packages:  rpm -qa |grep php   It prints out a list of packages, and I want to remove all them with:  rpm -e *pakage.name*   Can I iterate over all matches in grep results and use each match in:   rpm -e *grep.match* Security importance of Key Schedule in Block Cipher How can I limit ssh *remote* port forwarding? I need to limit which ports can be remotely 'ssh -R' forwarded by an user.  I know about permitopen option on authorized_keys, but as it says on man page it only limits local 'ssh -L' port forwarding  As discussed  a user would get the same with netcat or similar, but in this case user has no shell access  I also found  that talks about using selinux or LD_PRELOAD, but I never configured selinux before and can't find info on how to do that with LD_PRELOAD.  maybe someone have made a patch for openssh to implement that?  EDIT: I've found  so I guess it's not yet implemented How to make putty to not break my session after some time? Each time putty is closing the session after some time if it is idle.  There is no time parameter on putty, so how can I keep my putty ssh session always Alive? I've recently been learning about differential equations, and my teacher has been giving some particularly difficult examples out for those of us who finish early. He gave us the following differential equation: $$x=y\frac{dy}{dx}-\left(\frac{dy}{dx}\right)^{2}$$ With the hint "Differentiate with respect to $y$, then let $\frac{dy}{dx}=p$". I've solved it after the lesson and would like someone to check whether or not I've done so correctly.    Following the hint, $$\frac{dx}{dy}=\frac{1}{p}=p+y\frac{dp}{dy}-2p\frac{dp}{dy}$$ Which rearranges to $$p-\frac{1}{p}+y\frac{dp}{dy}=2p\frac{dp}{dy}$$ Multiplying through by $\frac{dy}{dp}$, $$\left(p-\frac{1}{p}\right)\frac{dy}{dp}+y=2p$$ Rearranging into the form $\frac{dy}{dp}+f(p)y=g(p)$, and writing $p-\frac{1}{p}=\frac{p^{2}-1}{p}$ $$\frac{dy}{dp}+\frac{p}{p^{2}-1}y=\frac{2p^{2}}{p^{2}-1}$$ Our integrating factor is $$e^{\int\frac{p}{p^{2}-1}dp}=e^{\frac{1}{2}\ln(p^{2}-1)}=\sqrt{p^{2}-1}$$ So we have $$\sqrt{p^{2}-1}\frac{dy}{dp}+\frac{p}{\sqrt{p^{2}-1}}y=\frac{2p^{2}}{\sqrt{p^{2}-1}}$$ The left hand side is, by design, $\frac{d}{dp}(y\sqrt{p^{2}-1})$, and the right hand side can be integrated as follows: $$\int \frac{2p^{2}}{\sqrt{p^{2}-1}}dp=\int\frac{2(p^{2}-1)+2}{\sqrt{p^{2}-1}}dp=\int 2\sqrt{p^{2}-1}dp+\int \frac{2}{\sqrt{p^{2}-1}} dp$$ These can both be solved using the substitution $p=\cosh(u)$, and gives $$y\sqrt{p^{2}-1}=p\sqrt{p^{2}+1}-\cosh^{-1}(p)+\alpha$$ Where $\alpha$ is an arbitrary constant. Dividing, we finally have $$y=p+\frac{\cosh^{-1}(p)+\alpha}{\sqrt{p^{2}-1}}$$  Here I was stuck for a long time, until I realised that we also have the equation we began with: $x=py-p^{2}$, which we can solve as a quadratic in $p$ to also get $$p=\frac{y\pm \sqrt{y^{2}-4x}}{2} \implies p^{2}=\frac{y^{2}+y^{2}-4x \pm 2y\sqrt{y^{2}-4x}}{4}$$  Thus, $$y=\frac{y\pm \sqrt{y^{2}-4x}}{2}+\frac{\cosh^{-1}\left(\frac{y\pm \sqrt{y^{2}-4x}}{2}\right)+\alpha}{\sqrt{\frac{y^{2}-2x \pm y\sqrt{y^{2}-4x}}{2}-1}}$$  This is as good as I can do - we have a relation between $y$ and $x$ - am I done? Is this the correct answer? Is there an easier way?     Thank you for your time.    Following the suggestion by @Valentin $$\frac{dy}{dp}=1+\frac{\frac{1}{\sqrt{p^{2}-1}}\sqrt{p^{2}-1}-p\frac{\cosh^{-1}(p)+\alpha}{\sqrt{p^{2}-1}}}{p^{2}-1}=1+p\frac{1-\frac{\cosh^{-1}(p)+\alpha}{\sqrt{p^{2}-1}}}{p^{2}-1}$$ Hence, $$dx=\frac{dy}{p}=dp\left(\frac{1}{p}+\frac{1-\frac{\cosh^{-1}(p)+\alpha}{\sqrt{p^{2}-1}}}{p^{2}-1}\right)$$ Probability that a quadratic polynomial with random coefficients has real roots The following is a homework question for which I am asking guidance.     Let $A$, $B$, $C$ be independent random variables uniformly distributed between $(0,1)$. What is the probability that the polynomial $Ax^2 + Bx + C$ has real roots?   That means I need $P(B^2 -4AC \geq 0$). I've tried calling $X=B^2 -4AC$ and finding $1-F_X(0)$, where $F$ is the cumulative distribution function.  I have two problems with this approach. First, I'm having trouble determining the product of two uniform random variables. We haven't been taught anything like this in class, and couldn't find anything like it on Sheldon Ross' Introduction to Probability Models.  Second, this strategy just seems wrong, because it involves so many steps and subjects we haven't seen in class. Even if I calculate the product of $A$ and $C$, I'll still have to square $B$, multiply $AC$ by four and then subtract those results. It's too much for a homework question. I'm hoping there might be an easier way. Is there a "theirs" version of "git merge -s ours"? When merging topic branch "B" into "A" using git merge, I get some conflicts. I know all the conflicts can be solved using the version in "B".  I am aware of git merge -s ours. But what I want is something like git merge -s theirs.   Why doesn't it exist? How can I achieve the same result after the conflicting merge with existing git commands? (git checkout every unmerged file from B)  UPDATE: The "solution" of just discarding anything from branch A (the merge commit point to B version of the tree) is not what I am looking for. Curve Object Deformed by Curve - Distortions (Artefacts) Shaping curve object by curve (modifier) results in a terrible shape with cracked surface. Here is an extreme situation, but good visible issue.  Perspective   Top   How can I curve it smootly without adding more control points or remeshing? Possible Duplicate:          On Wikipedia, it says that:     Matrix representation of complex numbers   Complex numbers $z=a+ib$ can also be represented by $2\times2$ matrices that have the following form: $$\pmatrix{a&amp;-b\\b&amp;a}$$   I don't understand why they can be represented by these matrices or where these matrices come from.