Question

How do you verify `cos^2(2alpha) - sin^2(2alpha)=cos(4alpha)`?

Answer 1

See below

Explanation:

LHS = left hand side, RHS = right hand side

LHS `=(1-sin^2 2alpha) - sin ^2 2alpha`

`=1-2 sin^2 2alpha`

`=cos2(2alpha)`

`=cos 4 alpha`

`=RHS`