Q35 of 35 Page 3

Prove that cos6x = 32cos6 x- 48cos4x + 18cos2x-1


cos6x  = 4 cos32x - 3 cos2x

          = 4(2cos2x-1)3 - 3(2cos2x-1)

          = 4[(2cos2x)3 - 3×(2cos2x)2×1 + 3 × 2 cos2x×1 - 13]-6cos2x + 3

          = 32cos6x - 48cos4x + 18cos2x -1

          = R.H.S

Hence proved

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