I tried to do that, but I found some problems, because eval is a @classmethod so the mechanism has to be different than for the other methods implemented in ReciprocalTrigonometricFunction. eval() follows a different pattern than the other methods rewrite, is,**, etc. would be nice if mechanism was homogenouse.

I will anyway keep playing around a bit with python to see if I manage to reuse the reciprocal class (sin/cos) implementation.