I really can't prove this, can you please show me how to do it?

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

Thank you so much!

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

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

Thank you so much! - Dec 10th 2012, 10:43 PMTutuRe: Proving!
Ignore this, I got it! Thanks!