sympy/sympy — pull request #8351 by skirpichev (2014-10-29 22:18:55+00:00)
Title: Improve _eval_is_algebraic helper for trigonometric numbers

Now for sin(pi*rational) or cos(pi*rational) - is_algebraic is True,
see: http://mathworld.wolfram.com/TrigonometryAngles.html

fixes #8349