How is sin2A + cos2A = 1?

1.	How is sin2A + cos2A = 1?
Answer» Now we proceed to the proof.Let alpha = x and beta = -x=> cos(x + (-x)) = cos(x)cos(-x) - sin(x)sin(-x)⇒cos(x+(−x))=cos(x)cos(−x)−sin(x)sin(−x)=> cos(0) = cos(x)cos(x) - (-sin(x)sin(x)):. 1 = cos^2(x) + sin^2(x) 2 Comments Sorry, yes he is right it is an identity It\'s an identity.

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