### How to simplify complicated expressions

Hello,

This complicated expression would be a zero function, but I can't achive to simplify it. I think I've run into lots of expressions like this one, but I've never come up with a solution.

This is mi code:

```
var('R d',domain='positive')
var('p',domain='real')
```~~var('t',domain='real',latex_name="\theta")~~var('t',domain='real',latex_name="\\theta")
~~ ~~f=(R*cos(t) f=(R*cos(t) - *~~d)~~p/(-2*R*d*cos(t) d)*p/(-2*R*d*cos(t) + R^2 + d^2)^(3/2) + *~~(R~~cos(t) -R^2/d)*R^3*p/((-2*R^3*cos(t)/d (R*cos(t) -R^2/d)*R^3*p/((-2*R^3*cos(t)/d + R^2 + ~~R^4/d^2)^(3/2)~~*d^3) +R*p/(sqrt(-2*R^3*cos(t)/d R^4/d^2)^(3/2)*d^3) +R*p/(sqrt(-2*R^3*cos(t)/d + R^2 + ~~R^4/d^2)*d^2)~~

R^4/d^2)*d^2