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"I would never die for my beliefs because I might be wrong."

-- Bertrand Russell


12h
comment Transforming a PDE given basis vectors
That's a gradient, it's $\frac{\partial u^i}{\partial x^k}e^k$.
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comment Transforming a PDE given basis vectors
Now, it would be neat if you gave me the example you want to do in detail so that I can see if it works out.
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14
comment Transforming a PDE given basis vectors
Don't worry, I'll continue. I just need some more time to work it out.
Dec
14
answered Transforming a PDE given basis vectors
Dec
14
comment Vector question involving an operator!
Compute the scalar product of both with $\mathbf n$ and compare.
Dec
13
revised Vector question involving an operator!
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Dec
13
answered Vector question involving an operator!
Dec
12
comment Transforming a PDE given basis vectors
How do you define $n$? Just because you've written $\mathbf g_n=\mathbf g_r\times \mathbf g_{\beta}$ does not mean that you have defined an $n$. I suppose you want to somehow define $n(r,\beta,z)$ such that $\partial \mathbf x/\partial n = \mathbf g_n$.
Dec
10
revised Could someone check my work on this exercise
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Dec
10
answered Could someone check my work on this exercise
Dec
10
comment Could someone check my work on this exercise
Well, it's just a matter of wording, technically a subgroup of a group of permutations is still a group of permutations. But your statement that every finite group is isomorphic to the alternating group is obviously false. What do you do about the group $S_4$ how do you map odd permutations on even permutations?
Dec
9
awarded  Caucus
Dec
9
comment Could someone check my work on this exercise
No, Cayley's theorem states that every group is isomorphic to a subgroup of a group of permutations. Also note that Cayley's theorem also includes infinite groups.
Dec
8
comment How many triangles in the picture?
Formula maybe not, but there definitely is an algorithm. Just start in one point, then form all triangles you can with that point as a corner, count them. Then remove that point from the diagram and choose a new point. Rinse, repeat.
Dec
8
comment Could someone check my work on this exercise
You mean $H \cap SO(n)$ is? Then yes, I think that's correct.
Dec
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comment Prove that $X_1 + … + X_r \sim NB(r,p)$
It lacks a sum over the different possible values of $j_2,j_3,\ldots,j_r$.