Hi guys, I need help on simplifying this trig equation, any help appreciated I have to show that cos((n+1).X) = 2cosn X .cosX - cos((n-1).X) But I do not know what steps to take. EDIT: I think this is in the wrong forum. sorry.
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Use the identity $\displaystyle \cos a+\cos b=2\cos\frac{a+b}{2}\cos\frac{a-b}{2}$ for $\displaystyle \cos(n+1)x+\cos(n-1)x$
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