Question

Warning: Extremely difficult. Please attempt this for me!!!

Prove the identity.

Answer 1

\[1-8\sin^2\theta \cos^2\theta =\cos(4\theta)\]

Answer 2

Use demoveries theorem.

Answer 3

1-2sinθcosθ*2sinθcosθ*2
1-2sin(2θ)sin(2θ)
1-2sin^2(2θ)
cos(2*2θ)
cos(4θ)

Answer 4

Great answer!!!

Answer 5

Wow @WolframWizard
You're a genius!

Answer 6

May I ask what your thought process was? I just can't seem to understand how you can figure this out.

Answer 7

I try to pull the expressions apart as much as possible so I can use identities to piece it back together into what I want.