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Dec
16
answered Why does the determinant $D$, have to be $0$ for equation to have a solution?
Dec
15
awarded  Tenacious
Dec
12
comment Boundary conditions Legendre equation
In your definition of $G$; do you mean to have a factor of $\frac{1}{\sqrt{\sin \theta}}$? You seem to be missing your argument.
Dec
11
comment Green's theorem vector form interal
You're welcome, Nick.
Dec
11
comment Differentiation under the integral sign, please help
Here, you are differentiating w.r.t $x$ and so you treat $y$ constant. If you are implying that there would be a "higher dimensions" issue then you can differentiate under the integral sign in higher dimesions, see en.wikipedia.org/wiki/…
Dec
11
comment Differentiation under the integral sign, please help
Consider it done :-)
Dec
11
revised Differentiation under the integral sign, please help
Included reference to Wolfram.
Dec
11
answered Differentiation under the integral sign, please help
Dec
11
comment Computing the infinite sum, $\sum_{n=0}^\infty \frac {5^n}{25^n + 1} $
Many thanks, that's great!
Dec
11
answered Green's theorem vector form interal
Dec
11
answered How to get matrix $A$ from $A^\top A=B$ with given symmetric matrix $b$?
Dec
11
comment Computing the infinite sum, $\sum_{n=0}^\infty \frac {5^n}{25^n + 1} $
Love this way of approaching it; one question though, why have you chosen to write $2 \cosh(-\ln(5)n)$ instead of noting that $\cosh$ is even? Is it something to do with the fact that the argument is a $\ln$?
Dec
11
comment Solve laplace equation inside a rectangular
Ah gosh, didn't read that far down; I'm working on it...
Dec
11
comment Solve laplace equation inside a rectangular
Why not find the general 2D solution to Laplace's equation, using separation of variables (i.e. $u(x,y)≡X(x)Y(y)$) and then substitute your boundary conditions to find the particular solution?
Dec
11
revised Is $(-\infty, \infty)$ an interval?
Just added a little latex to the question.
Dec
11
suggested approved edit on Is $(-\infty, \infty)$ an interval?
Dec
9
comment Laplace transform of piecewise function
Check your first limit where $t=1$, you should end with $-s^{-2}(se^{-s}+2e^{-s})$
Dec
9
awarded  Caucus
Dec
9
comment Finitely generated modules
Hi there, intended to do that but deleted part of it that wasn't relevant. I deleted the comment I wrote about it being somebody else's answer, I perhaps should've just posted a link to the other question. Many thanks.
Dec
5
answered general idempotent matrix possible values of the determinant