Question #88d71

1 Answer
Manikandan S.
Jan 8, 2018

Proven

Explanation:

cos4x = cos(2x+2x)
cos4x = cos^(2)2x-sin^(2)2x
cos4x = 1-sin^(2)2x-sin^(2)2x
cos4x = 1-2sin^(2)2x
cos4x = 1-2(2sinxcosx)^2
cos4x = 1-2(4sin^2xcos^2x)
cos4x = 1-8sin^2xcos^2x

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