# Complex numbers in polar form

1. Aug 19, 2009

### seboastien

1. The problem statement, all variables and given/known data
Evaluate the square 0f 5e^(3(pi)i)/4 without using Cartesian form, and also the three different products.

2. Relevant equations
e^i(theta) = cos(theta) + isin(theta)?

3. The attempt at a solution
I have absolutely no idea here, nothing in my notes even begins to suggest how I can answer this.

2. Aug 19, 2009

### Cyosis

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.

3. Aug 19, 2009

### seboastien

yes but what do they mean by the 3 products?

4. Aug 19, 2009

### Cyosis

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

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

5. Aug 19, 2009

### seboastien

it says to evaluate the three products of the complex number

6. Aug 19, 2009

### Cyosis

Then just remove the 'nots' in my previous post.