Verify the identity.sin(x + y) cos(x - y) = sin x cos x + cos y sin y
What will be an ideal response?
sin(x + y) cos(x - y) = [sin x cos y + cos x sin y][cos x cos y + sin x sin y]
= sin x cos x cos2 y + cos y sin y sin2 x + sin y cos y cos2 x + cos x sin x sin2 y
= sin x cos x(cos2 y + sin2 y) + cos y sin y(sin2 x + cos2 x)
= sin x cos x + cos y sin y
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