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]