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David Z's user avatar
David Z's user avatar
David Z's user avatar
David Z
  • Member for 13 years, 11 months
  • Last seen this week
59 votes
8 answers
17k views

Why doesn't induction extend to infinity? (re: Fourier series)

11 votes
3 answers
6k views

Is any divergence-free curl-free vector field necessarily constant?

11 votes
3 answers
1k views

What's the term for a "physical vector space"?

10 votes
1 answer
362 views

What's the right way to make a change of variables under another integral?

5 votes
2 answers
3k views

How do I write the 2D Dirac delta in a manifestly rotationally invariant form?

5 votes
1 answer
974 views

How can I prove this identity involving the digamma function?

5 votes
1 answer
348 views

Asymptotic behavior of an integral involving the gamma function

4 votes
1 answer
3k views

What kind of quadrilateral is determined by four sides and a diagonal?

4 votes
2 answers
1k views

What does the Fourier transform of $1/x^2$ mean?

3 votes
0 answers
558 views

How can I integrate a Bessel function divided by a "shifted" value?

3 votes
1 answer
843 views

Proving an identity involving the derivative of the Laguerre polynomials with respect to $n$

2 votes
0 answers
213 views

Do the classical Lie algebras all satisfy $XM + MX^T = 0$?

2 votes
1 answer
73 views

Necessary/sufficient conditions to express numbers as differences of other numbers

2 votes
1 answer
117 views

Large-z limit of the *other* second derivative of the Laguerre polynomial

2 votes
1 answer
148 views

Symbolically solving coupled partial differential equations

2 votes
2 answers
365 views

Is it always possible to choose 2-partitions of a set that cover the maximum number of pairs without repeating?

1 vote
1 answer
794 views

Does an inward vector field on a boundary require a zero point or singularity in the interior?

1 vote
1 answer
449 views

Is there a known simple mental approximation to a hypergeometric distribution?

0 votes
2 answers
177 views

Why would the eigenvalues of this type of (stochastic) matrix all be close to 1?

0 votes
1 answer
118 views

Is there a standard name for one period of a triangle function?

0 votes
1 answer
3k views

Solving an equation with a "nested" function: $f(t_1 + t_2, K) = f\bigl(t_2, f(t_1, K)\bigr)$