I have the following code in sympy
from sympy import *
x,y,G=symbols('x y G')
G=x**(3./2.) - y
g_inv=solve(G, x)
if len(g_inv)>1: g_inv=g_inv[-1]
dginvdy=diff(g_inv, y)
The problem is that this gives me
____
3 ╱ 2
2⋅╲╱ y
─────────
3⋅y
and not 2*y**(-1./3)/3 as I expected. I have tried simplify() and even cancel() but no luck. Also, if I define the variables with real=True I can't invert it with solvefor some reason. If I define only yas being real I get
2⋅sign(y)
─────────
3 _____
3⋅╲╱ │y│
which is closer (?) but still not what I want. Defining y as positive also didn't do the trick.
This may seem like something silly but it tremendously complicates the calculations I do from then on.
Any ideas?
I think you need to use sympy.factor here rather than simplify:
In [2]: dginvdy
Out[2]: 2*(y**2)**(1/3)/(3*y)
In [3]: factor(dginvdy)
Out[3]: 2/(3*y**(1/3))
The sympy docs go into some detail about this.