Best way to convert complex numbers, rect, polar, euler

[blevita]

Hello

I have tried several ways to convert complex numbers between differents formats.
What i am looking for is a way to convert all of them between all formats.
As example:

polar to cartesian: r * exp(i*phi) => a+ib
cartesian to euler: a+ib => r(cos(phi)+ i*sin(phi) )

is there a simple command or trick to easily do this conversion?
Or do i have to write a program for that?

Thanks