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21h
comment What interpretation of the Lie braket is this?
What is $\partial/\partial x$? What is curly-$X$? I also doubt that $[\ ,\ ]$ is the Lie bracket since otherwise bilinearity gives you $X=2X$.
21h
comment Need some help understanding this exercise about injective plane curve
Why do you say $\gamma$ is a diffeomorphism? It's not even a homeomorphism (for one thing, the dimensions of the domain and range don't match.)
21h
comment What interpretation of the Lie braket is this?
The link doesn't show the page for me. Could you reproduce the definitions and exercise?
22h
awarded  Revival
1d
revised Is there a closed-form solution to the following equation?
added 4 characters in body
1d
answered Is there a closed-form solution to the following equation?
1d
answered derivative of gradient involving inverse of matrices
2d
comment If $\det A=1$ and the matrices $A^{2015}$ and $A^{2017}$ are integer, is $A$ an integer matrix?
This is a nice problem. I'm tempted to obfuscate it even further by replacing $\mathbb{Z}$ with a ring like $\mathbb{Z}/2^{64}\mathbb{Z}$ ("matrices using computer integer arithmetic") and 1 with a different unit.
2d
answered Determinant of symplectic matrix
2d
answered Values of $a$ for which $ f(x)=8 a x-a \sin6x -7x - \sin 5x $ increases
2d
comment Regarding functions from R² to R: continuity and differentiability
@SantiagoCanez Quite right; fixed.
2d
revised Regarding functions from R² to R: continuity and differentiability
deleted 5 characters in body
2d
answered Regarding functions from R² to R: continuity and differentiability
May
26
comment Applying orthogonality of Sines to this question.
What is a "driven function"?
May
26
comment Any program that turns vectors to orthogonal?
I suppose the tricky part is not checking orthogonality, but rather checking that the vectors still span the right space.
May
26
comment relation between trace of product and sum of matrices?
@GerryMyerson Tightened the inequality appropriately.
May
26
revised relation between trace of product and sum of matrices?
added 168 characters in body
May
26
comment relation between trace of product and sum of matrices?
@GerryMyerson Right, I think that 2 can be made a 4 as well in this case.
May
26
revised relation between trace of product and sum of matrices?
added 26 characters in body
May
26
answered relation between trace of product and sum of matrices?