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Jul
28
awarded  Popular Question
Jul
19
revised Bound the pseudo-inverse matrix of a product
Typo
Jul
18
comment Proof by Induction $n^2+n$ is even
You know you don't need induction, do you?
Jul
18
asked Bound the pseudo-inverse matrix of a product
Jul
7
answered How to use Galerkin approximation to find the existence of weak solution.
Jul
6
accepted The Betti numbers of a triangulated ball relative to a disk in its boundary
Jul
6
revised The Betti numbers of a triangulated ball relative to a disk in its boundary
clarification
Jul
6
asked The Betti numbers of a triangulated ball relative to a disk in its boundary
Jun
20
asked Slobodeckij and Bessel definitions of fractional Sobolev spaces on Lipschitz domains
May
24
asked Example for $\Omega$ so that $\partial\Omega \neq \partial\bar{\Omega}$
Apr
30
accepted Cyclic containment of sets
Apr
22
awarded  Nice Question
Apr
7
comment Antisymmetric functions in higher dimensions
Okay, maybe a nice definition of signed permuation of coordinates is a permuation matrix times a ${-1,1}$-diagonal matrix, and the signum is the determinant of that transform.
Apr
7
comment Antisymmetric functions in higher dimensions
That's interesting. Your functions are smooth, are they? And could you please define what a signed permuation and its signum mean?
Apr
2
asked Cyclic containment of sets
Mar
18
comment How should I understand “$A$ unless $B$”?
That post is nicely written. Thanks!
Mar
13
comment Derivative in complex analysis
@anon: I am curious and my complex analysis is rusty, too. Why is $f$ constant?
Mar
13
answered I have to show that the matrix $M^TM$ is SPD if and only if the columns of the matrix M are linearly independent
Mar
7
awarded  Tumbleweed
Mar
7
comment Which formula do I use to integrate $ \int {\sqrt{x^2 + 81} \over 2} \,dx $
In your final expression, the variable $x$ appears outside the integral, without any proper definition there. You should change this notation.