Question

prove that cos2A=cos^2A-sin^2A​

Answer 1

Answer:

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Step-by-step explanation:

Answer 2

Answer -

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• Now, putting B = A on both sides of the above formula we get,cos (A + A) = cos A cos A - sin A sin A⇒ cos 2A = cos2 A - sin2 A⇒ cos 2A = cos2 A - (1 - cos2 A), [since we know that sin2 θ = 1 - cos2 θ]⇒ cos 2A = cos2 A - 1 + cos2 A,⇒ cos 2A = 2 cos2 A - 1⇒ cos 2A = 2 (1 - sin2 A) - 1, [since we know that cos2 θ = 1 - sin2 θ]⇒ cos 2A = 2 - 2 sin2 A - 1⇒ cos 2A = 1 - 2 sin2 A

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