trigsimp and expand_trig rewrite identities.

Goal

Simplify sin^2+cos^2 and expand sin(2x).

import sympy as sp
x = sp.symbols('x')
print(sp.trigsimp(sp.sin(x) ** 2 + sp.cos(x) ** 2))

import sympy as sp
x = sp.symbols('x')
print(sp.expand_trig(sp.sin(2 * x)))

import sympy as sp
x = sp.symbols('x')
print(sp.simplify(sp.sin(x) / sp.cos(x)))

import sympy as sp
print(sp.sin(sp.pi / 6))