# Proving!

• Dec 10th 2012, 08:53 PM
Tutu
Proving!
I really can't prove this, can you please show me how to do it?

If z=cis $delta$, prove that $z^n$ + $\frac{1}{z^n}$ = 2cosn $delta$

Thank you so much!
• Dec 10th 2012, 10:43 PM
Tutu
Re: Proving!
Ignore this, I got it! Thanks!