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Prove :sin x + sin 3x + sin 5x + sin 7x = 4 cos x cos 2x cos 4x |
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Answer» sinx+sin3x+sin5x+sin7x sinx+7x+sin3x+sin5x 2 C+D
2 C−D
Now, 2sin( 2 x+7x
)cos( 2 x−7x
)+2sin( 2 3x+5x
)cos( 2 3x−5x
) 2sin4xcos3x+2sin4xcosx 2sin4x(cos3x+cosx) 2sin4x[2COS 2 C+D
cos 2 C−D
] 2sin4x[2cos 2 3x+x
cos 2 3x−x
] 2sin4x×2cos2xcosx 4sin4xcos2xcosx.
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