Question: a. Using the identity cos (A + B) cos A cos B sin A sin B, show that cos 2A cos 2

a. Using the identity cos (A + B) ≡ cos A cos B − sin A sin B, show that cos 2A ≡ cos2 A − sin2 A.

b. Hence show that:

i. cos 2A ≡ 2 cos2 A − 1

ii. cos 2A ≡ 1 − 2 sin2 A

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