# Complex numbers in polar form

## Homework Statement

Evaluate the square 0f 5e^(3(pi)i)/4 without using Cartesian form, and also the three different products.

## Homework Equations

e^i(theta) = cos(theta) + isin(theta)?

## The Attempt at a Solution

I have absolutely no idea here, nothing in my notes even begins to suggest how I can answer this.

Cyosis
Homework Helper
All you really need to know is the equation you listed. The square of e^x is (e^x)^2=e^(2x), use this information to solve your problem.

yes but what do they mean by the 3 products?

Cyosis
Homework Helper
With not using the three products I would guess they mean to not use:

$$(\cos x+i\sin x)^2=\cos^2x-\sin^2 x+2i\cos x \sin x$$

it says to evaluate the three products of the complex number

Cyosis
Homework Helper
Then just remove the 'nots' in my previous post.