So just as a reminder we know that you can represent a complex number z as:
in rectangular coordinates or
where and in polar coordinates (you have to adjust theta for the quadrant depending on the signs on x and y).
By Euler's formula we can change the second e like this:
So actually, now that I've done that.. it's not going to work out at all unless you actually meant:
So you need an 'i' term with the term.
So yeah... If there wasn't a typo, perhaps some of my rambling will jog your memory.