Simplifying expressions using Euler's formula

[Sunwoo Bae]

Homework Statement

Simplify the following expression using euler's formula. (The problems in the pic)

Relevant Equations

e^i Θ = cos Θ+isin Θ

The following is the questions given. I solved the first one, which steps are shown below.

But I am not sure if this is how the question wants me to solve the problem. Would you tell me if the way I solved the problem is the proper way of simplifying the expression using euler's formula?

Also, I did try problem b, but I am not sure how to proceed or where to use the euler's formula.

Thank you for your help!

 

[PeroK]

Using Euler's formula means expressing the the complex numbers in polar form, like you did for question a).