sympy/sympy — pull request #1258 by ness01 (2012-04-21 21:10:08+00:00)
Title: Trigsimp using groebner bases

So, after spamming the list long enough, here is the pull request, finally. This is essentially a proof of concept implementation of trigsimp using ratsimpmodprime, implemented by Jerryy.

It can do some fun stuff, but gets slow quickly as the complexity of the input increases. I don't know if a "real-world" trigsimp based on this can ever work.