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Prove that sinx + sin3x + sin5x + sin7x = 4cos x cos2x sin4x |
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Answer» LHS = (sin7x + sin x) + (sin5x + sin3x) = 2sin4xcos3x + 2sin4xcosx = 2sin4x(cos3x + cosx) = 2sin4x2cos2x cos x = 4cosxcos2xsin4x = RHS. |
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