# Complex Numbers

• Nov 3rd 2013, 06:41 AM
anil86
Complex Numbers
This is a thread for complex number problems in applied mathematics.

You can see attachment for the question.
• Nov 3rd 2013, 02:40 PM
SlipEternal
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.
• Nov 4th 2013, 12:28 AM
anil86
Re: Complex Numbers
I tried that but can't get the solution. Can you solve & illustrate it to me?
• Nov 4th 2013, 12:41 AM
SlipEternal
Re: Complex Numbers
• Nov 20th 2013, 12:46 AM
anil86
Re: Complex Numbers
Thanks for replies. I got the solution.
• Nov 20th 2013, 12:51 AM
anil86
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.
• Nov 20th 2013, 03:41 AM
topsquark
Re: Complex Numbers