implement trigonometric symmetry simplifications

[rwst]

This will bring Sage to its knees:

assert sin(104*pi/105) == sin(pi/105)

because sin symmetry is not implemented and so the __nonzero__ proof machinery is started which uses QQbar on algebraic numbers of high degree.

Sympy immediately verifies the equation because it does:

>>> sin(104*pi/105)
   ⎛ π ⎞
sin⎜───⎟
   ⎝105⎠

The fix will be made in Pynac and this ticket should doctest it.

Component: symbolics

Issue created by migration from https://trac.sagemath.org/ticket/20139

[rwst]

comment:2

This works in develop and is tested in Function_sin so can be closed.

[embray]

comment:4

Determined to be invalid/duplicate/wontfix (closing as "wontfix" as a catch-all resolution).