Question

prove that cos4x=1-8sin xsquare cos square x solve it detail

Answer 1

cos2×2x= 1-2sin^2(2x)
= 1-2×(2sinxcosx)^2
=1-8sin^2xcos^2x

Answer 2

cos4x=cos2(2x)

cos4x=1-2sin²2x

cos4x=1-2(sin2x)²

cos4x=1-2(2sinxcosx)²

cos4x=1-2(4sin²xcos²x)

cos4x=1-8sin²xcos²x