# Math Help - Complex Numbers

1. ## Complex Numbers

This is a thread for complex number problems in applied mathematics.

You can see attachment for the question.

2. ## Re: Complex Numbers

What help do you need? What do you have so far? For the first one, I would start with multiplying out by $2(1-\cos \theta)$ and see what you get (consider the sum or difference of angles formula for cosine).

For the second problem, again, I would start with the difference of angles formula for cosine.

3. ## Re: Complex Numbers

I tried that but can't get the solution. Can you solve & illustrate it to me?

5. ## Re: Complex Numbers

Thanks for replies. I got the solution.

6. ## Re: Complex Numbers

Solve equations using De Moivre's theorem:

1. x^7 + x^4 + x^3 + 1 = 0

2. x^7 - x^4 + x^3 - 1 = 0

I tried multiplying with (x - 1). Also tried putting x^3 = y; didn't work.