Problem:
Find the fourth order expansion about $x = 0$ of the composition $f(g(x))$ for $f(x) = \log (x)$ and $g(x) = $\tanh (x)$
from sympy import *
from sympy.abc import x

f = log(x)
g = tanh(x)
series = f.subs(x, g).series(x, 0, 4)
print(series)
