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Cos4x=1-8sin"xcos" x. ( " squre) |
| Answer» 4x=2×2x let 2x=∆ now, cos2∆=1-2sin"∆put value of ∆=2xcos4x =1-2(sin 2x)". sin2x =2sinxcosx cos4x =1-2(2sinxcosx)" cos4x =1-2(4sin"xcos"x) cos4x =1-8sin"xcos"x | |