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Question
Prove that sin2(A + B) – sin2(A – B) = sin2A sin2B
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Solution
sin2 A – sin2 B = sin(A + B) sin(A – B)
L.H.S = sin2(A + B) – sin2(A – B)
= sin[(A + B) + (A – B)] [sin(A + B) – (A – B)]
= sin 2A sin 2B
= R.H.S
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