Question

Use an angle sum identity to verify the identity cos 2 (theta) = 2 cos^2 (theta) - 1

Answer 1

Rewrite it like this.
\[\cos(2\theta)=\cos(\theta + \theta)\]
Then you need to remember your angle sum identity for cosine :)
\[\cos(\alpha+\beta) = \cos \alpha \cos \beta - \sin \alpha \sin \beta\]

See if you can figure it out from there! :)

Answer 2

So, 2+2? for a + b?

Answer 3

Theta + Theta for a and b :\