sympy/sympy — pull request #1577 by zanzibar7 (2012-10-13 19:56:02+00:00)
Title: changed tan and cot expansion, eval, and rewrite

* added expand(trig=True) for tan(x+y), tan(n*x), cot(x+y), cot(n*x)
* call sin and cos now to eval tan,cot at rational multiples of pi
* provide .rewrite(pow) and .rewrite(sqrt) for tan and cot
* added tests for tan and cot expansions
* added tests for rewrite(pow) and rewrite(sqrt)
* fixed tests in geometry to avoid eval of tan
* fixed a test in pretty printing to avoid eval of tan(pi/5)

This is an extension of my previous contributions to the trig functions