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 Aug15 comment Why does $\frac{\partial^2f}{\partial x \partial y} = \frac{\partial^2f}{\partial y \partial x}$ You need $f$ to be $C^2$, I believe. Aug13 comment Are electrodynamic problems in the complex plane relevant to real life? Maybe you should ask this in Physics.SE? Aug10 comment Is my proof correct about limit of $\sin\left(\frac{1}{x}\right)$? It's not a big deal, but you should mention what happens when $|A| > 1$. Aug7 comment Differentiate $\ln(\cos2x)$ With respect to $x$. @Amzoti: Please, there's no need to be like that. I understand what you wrote, and the asker of the question does too. But if you read my comment, you'll see that not only did I not even begin to imply that something was offensive, but also that I think that writing things like $\ln u =\frac1{u}$ only helps further the confusion of students who write that when asked to differentiate $\ln u$. Aug7 comment Differentiate $\ln(\cos2x)$ With respect to $x$. Yes, please don't write things like $\ln u = \frac1{u}$. Students are confused enough already. Either say $(\ln u)'$, or $\frac{d}{du}\ln u$, or else "the derivative of $\ln u$ is $\frac1{u}$". Aug6 comment Are parallel vectors always scalar multiple of each others? @AmitTomar: So really any lines that don't intersect? Because that's not the definition of parallel. Aug6 comment Are parallel vectors always scalar multiple of each others? Could you clarify what you mean by parallel lines that are not in the same direction? Do you mean parallel lines that don't touch, or do you mean lines that have different direction vectors and don't intersect? The latter are called skew lines. Aug6 comment Are parallel vectors always scalar multiple of each others? @Kaster: I think I may be misunderstanding the OP's question. Let me ask. Aug6 comment Are parallel vectors always scalar multiple of each others? @user142526: I din't word that very well. Let me fix it. Aug5 comment Explain this step in logarithms Your answer seems fine. Aug3 comment Trying to reverse an equation and solve for a different variable Well, technically you can't reverse it, since because of the floor function many different xps will give the same level. But you can find out the minimum xp required to reach each level (I'm assuming this is for a game). Jul31 comment Prove: $\int_0^{\infty}\left(\frac{\sin x}{x}\right)^2dx=\pi/2$ Presumably you mean $|x| \le \delta$ instead of $x \le |\delta|$ in the definition of $f$? Jul27 comment Dot Product/ Cross Product Proof You're using the same $\theta$ for everything. That's not correct. Jul21 comment How can the graph of a complex function be embedded in three dimensional space? @JoeHobbit: What do you mean? Could you give an example? Jul18 comment is this the right truth table? Small nitpick: the fifth row is correct too. Jul14 comment Unique root to a function Words?${}{}{}{}{}{}$ Jul9 comment Evaluate $\int \limits_{0}^{\infty} \frac{x}{1+x^2} dx$ If you could overcome lack of convergence, no one would bother with convergence tests. Jul8 comment Incorrect notation in math? Isn't it $-3/2$ in the exponent? Jul8 comment Incorrect notation in math? All those notation are correct, if a bit confusing. But there exist incorrect notations, of course. Jul7 comment Complex integral $\frac {1}{1+z}$ I'm not sure I understand what path you're supposed to integrate on.