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Martin Cohen is a retired computer programmer who loves dancing (favorites are West Coast Swing, Waltz, Foxtrot, and Salsa), writing (but not revising) poems, and solving math problems (that's why I'm here). He is currently trying to learn improv at the Westside Comedy Theater (westsidecomedy.com) in Santa Monica, CA.

He can also be reached at mjcohen@acm.org.


1d
comment Finding relationship between two numbers directly that were changed cumulatively
What does the documentation say?
1d
answered Solve for x when x is on both sides of modular equation
1d
comment Search for summation formula
I think these are related to the Stirling numbers, but, upon looking them up, the relation is not clear to me. Thought I'd mention it anyway.
1d
answered Finding relationship between two numbers directly that were changed cumulatively
1d
comment tests for convergence of cos(pi/2n-1)-cos(pi/n)
As to $\sum (-1)^{n+1} \cos(\pi/n)$ diverging, it does but in an interesting way: Just like 1-1+1-1+1... it has only two limit points.
1d
comment Limit by L'hospital's rule
That is certainly the long way around. I am impressed that your result agrees with the other two.
1d
answered Derivative of $y=\tan(3)e^x$,
1d
answered how can i change specifically the intervals of a double integral?
2d
comment How do I prove that $\sum_{k=1}^{b-1} [k \frac{a}{b}] = \frac{(a-1)(b-1)}{2}$?
I looked at the link again and it seems to match OP's result. Have you checked it?
Oct
22
comment Proof of Descartes' theorem
Good old sci.math. I used to spend a lot of time there. Wonder if Archimedes Plutonium is still there with his disproof of Fermat's last theorem and other stuff.
Oct
22
answered Android application like mathjax
Oct
22
comment Proof of Descartes' theorem
Very nice proof - probably not written off the top of your head.
Oct
22
answered How do I prove that $\sum_{k=1}^{b-1} [k \frac{a}{b}] = \frac{(a-1)(b-1)}{2}$?
Oct
22
revised Solve recurrence relation problem
made the expressions look nice
Oct
22
answered Proving a set is a basis for a subspace
Oct
22
answered Prove that sequences $\frac{a_n}{b_n} = 0$
Oct
21
answered Prove the implication $[\exists\,x\;(\,p(x) \land q(x))] \implies[(\exists\,x\;p(x)) \land (\exists\,x\;q(x))]$ is a tautology.
Oct
21
comment If $f(x) = \sum \limits_{n=0}^{\infty} \frac{x^n}{2^{n(n-1)/2} n!}$ then $f^{-1}(f(x)-f(x-1))-\frac{x}{2}$ is bounded
Why do you think this is true?
Oct
20
comment Find asymptotics in a given form $n=(e+o(1))^{f(s)}$
I don't recall that. A reference would be nice. Also, what is the range of $k$ for which the approximation holds?
Oct
20
answered Prove that $\sqrt[4]{1+y^4} \leq 1+|y|$