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 Apr 5 awarded Yearling Feb 29 comment Newton's Law of Cooling and General advice on modeling with ODE Ok, I think I understand now. I'm not feeling well now, but I'll circle back and try to provide an answer in a couple of days. Feb 29 comment Newton's Law of Cooling and General advice on modeling with ODE What do you mean by "I know the question for this answer "? I'd like to give some advice, but I'm not sure exactly what you're asking. Feb 29 comment How to rotate the positions of a matrix by 90 degrees @mvw, ok I've removed the downvote for now. When I evaluated the answer I thought it was complete. Feb 29 comment How to rotate the positions of a matrix by 90 degrees @mvw, is your answer unfinished? Feb 29 comment How to rotate the positions of a matrix by 90 degrees I downvoted because I agree with Théophile. If the answer changes to answer the OP's question I will remove the downvote. Feb 28 comment Fundamental Theorem of Line Integrals Semi Proof This link also math.stackexchange.com/questions/1674064/… Feb 28 comment Fundamental Theorem of Line Integrals Semi Proof Hope that helps. Feb 28 answered Fundamental Theorem of Line Integrals Semi Proof Feb 28 comment Fundamental Theorem of Line Integrals Semi Proof $\nabla f = \vec{r}$ in this case to answer your question. Feb 28 comment Fundamental Theorem of Line Integrals Semi Proof math.stackexchange.com/questions/1674044/… Feb 28 comment Fundamental Theorem of Line Integrals Semi Proof This question was asked yesterday, by someone who was using multiple accounts to post related questions. Was that also you? Feb 27 revised Why isn't there a formula for $\zeta(k)=\sum_{n=1}^\infty\frac{1}{n^k}$ involving $\pi$ when $k$ is odd? deleted 2 characters in body Feb 27 revised Why isn't there a formula for $\zeta(k)=\sum_{n=1}^\infty\frac{1}{n^k}$ involving $\pi$ when $k$ is odd? added 5 characters in body Feb 27 revised Why isn't there a formula for $\zeta(k)=\sum_{n=1}^\infty\frac{1}{n^k}$ involving $\pi$ when $k$ is odd? Forgot some factors of $\pi$ Feb 27 answered Why isn't there a formula for $\zeta(k)=\sum_{n=1}^\infty\frac{1}{n^k}$ involving $\pi$ when $k$ is odd? Feb 27 answered Show that $\int_{c}{\textbf{r}\cdot d\textbf{r}} = \frac{1}{2}[||\textbf{r}(b)||^2 - ||\textbf{r}(a)||^2]$ Feb 27 comment Show that $\int_{c}{\textbf{r}\cdot d\textbf{r}} = \frac{1}{2}[||\textbf{r}(b)||^2 - ||\textbf{r}(a)||^2]$ To elaborate on T.Bongers' statement, in the line he is referring to the partial derivative operator appears out of nowhere. What would be correct is $\nabla \frac12 \| x \|^2 = x$. Feb 20 comment Fourier Transform Basics In general the statement is not true. $e^{i 3.1\xi}$ has a norm of $1$ but when expanded in an infinite Fourier series it has more than two nonzero coefficients. Are there any special conditions on the sequence $f(n)$? Feb 20 comment Fourier Transform Basics To answer your question the fact you observed can be shown formally for any finite sequence. Just use the distributive property.