Hi

Prove That : cos6A = 32cos^6A - 48cos^4A + 18cos^2A - 1.

To prove: cos 6a = 32cos6a - 48 cos4 a + 18 cos2 a - 1

Proof: 

cos6A= cos 2(3a)

= 2cos23a -1 = 2(cos 3a)2 -1 

= 2 (4cos3a - 3cosa)2 - 1

= 2(16 cos6 a + 9 cos2a - 24 cos4a) - 1

= 32cos6a + 18 cos2 a - 48 cos4 a - 1

= 32cos6a  - 48 cos4 a + 18 cos2 a  - 1 = RHS [Hence Proved]

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