prove that

Asked by  | 30th Jul, 2012, 03:34: PM

Expert Answer:

cos 4A
= cos 2(2A)
= 1 - 2 sin22A
= 1 - 2 (2sinA cosA)2
= 1 - 8 sin2A cos2A
= 1 - 8 sin2A (1- sin2A)
= 1 - 8 sin2A + 8 sin4A

Answered by  | 30th Jul, 2012, 03:54: PM

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