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bio website silvia-hi.me
location China
age
visits member for 3 years, 1 month
seen 2 days ago

I'm interested in data visualization, image processing, ODE/PDE, natural language processing, etc.

I'm currently a freelancer of Mathematica programming / Mandarin teaching / logo design.

Email addr: aquilaabz AT gmail.com; or:

1:eJztk8ENwzAIRUkHyA5ZqdfeMkC6/605Vl8Gg8EykUD6imMb8/hxjvP7vl5EtN/63NpKpVIpqSgBg4XzKbwzvP6PJ/Baa2BvxMxzea1caV2al3zQnId7pHqS1yPsEkPPa8/Yk4c8MzmwjuSNtydp3DsHg/PMwov7o74/ntni4f6nSAbuXcPK8YzyYqy+16u8tnrmYYnq07LOee3pKcJrzX3XrHPnjdaz/if47NVqsWl4tBrJmalsPJF9ZegNYzVPKZ9+c/YGIg==


Aug
23
comment Simplify $\tan^{-1}[(\cos x - \sin x)/(\cos x + \sin x)]$
define simplest please.
Jul
21
comment Method for variable substitution in multiple summation
Yes they are:( I used one of the explicit sum formulas of Chebyshev polynomial (mathworld.wolfram.com/ChebyshevPolynomialoftheFirstKind.html eq.15), which introduces those floor functions.
Jul
21
comment Method for variable substitution in multiple summation
@ Christian Blatter: Thanks very much for your answer. I understand the difficulties of counting lattice points in disk, but if considering the summation region bounded only by integer coefficients planes (like $\sum_k A_k x_k=B$ where $A_k, B\in \mathbb{Z}$), the problem might be much simpler and there might even exist a systematical technique for it. Besides, I'm thinking of using Iverson's bracket to avoid dealing with those tricky boundary conditions.
Jul
21
comment Method for variable substitution in multiple summation
@Patrick Da Silva: Yes I draw 2-dim or 3-dim axes too when I do the transformation by hand :D But if I have many levels of sum, this will be inefficient cause it's hard to draw high dimension, and those floor and ceiling functions and steps$\neq 1$ are bothering. I think I need to treat the whole summation region as a high dimension polyhedron and find a systematical routine to deal with it.