# Complex Exponentials

## Homework Statement

Ok So I'm doing some quantum questions and i have:

psi = Ae^i(kz-wt) + Be^-i(kz+wt).

How can i write this as a single exponential in the form psi = |psi| e^ i theta?

Thanks!

## The Attempt at a Solution

Not sure really..

I guess |psi| = |A+B| ?

how do i get an expression for e^itheta?