Question

If n is an integers then prove that cos(nπ+ A) =(-1)^n cosA.​

Answer 1

∵ cos(nπ) = (-1)ⁿ,

It follows that  :

cos(2nπ) = (-1)²ⁿ = [(-1)²]ⁿ = 1ⁿ = 1

cos(nπ) = (-1)ⁿ means that :

• cos(nπ) = 1 if n is even

• cos(nπ) = -1 if n is odd

∵ 2n is even, cos(2nπ) = 1

Hence Proved!!!

Answer 2

Answer:

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