Hey there.

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).

Anyways,

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.