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Prove that sin 4A = 4sinA cos3A – 4 cosA sin3A. |
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Answer» L.H.S. = sin 4A = 2 sin 2A- cos 2A = 2(2 sin A cosA)(cos2 A – sin2 A) = 4 sin A • cos3 A – 4 cos A sin3 A = R.H.S. |
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