Use De Moivre's Theorem to show that for any n greater that equal to 1(adsbygoogle = window.adsbygoogle || []).push({});

(1+itanθ)^{n}+ (1-itanθ)^{n}=2cosnθ/cos^{n}θ

where cosθ ≠ 0

I tried to approach this by converting into modulus argument form but wasn't really sure if that was correct. It's a common New South Wales HSC question but I couldn't find a solution anywhere. Help would be greatly appreciated :)

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# Homework Help: Use De Moivre's Theorem to prove this:

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