# How to convert "cos(th)+i*sin(th)" to "e^(i*th)"?

This question is perhaps trivial but annoying. I don't expect a quick answer.

The following are all I have tried.

```
sage: th = var('th')
----------
sage: e^(I*th).simplify_trig()
e^(I*th)
sage: e^(I*th).simplify_exp()
e^(I*th)
sage: e^(I*th).simplify_full()
e^(I*th)
----------
sage: f = cos(th) + I*sin(th)
sage: f.simplify_trig()
I*sin(th) + cos(th)
sage: f.simplify_exp()
I*sin(th) + cos(th)
sage: f.simplify_full()
I*sin(th) + cos(th)
```

Thanks for your patience in advance!