Question

Prove that cos 6x=32cos6x - 48cos4x + 18cos2x-1​

Answer 1

answer:

Using,

cos2x=2cos

2

x−1

cos3x=4cos

3

x−3cosx

LHS:

cos6x=2cos

2

3x−1

=2(4cos

3

x−3cosx)

2

−1

=2(16cos

6

x+9cos

2

x−24cos

4

x)−1

=32cos

6

x−48cos

4

x+18cos

2

x−1 = RHS