cos(α − β)cos(α + β) = cos2α - sin2 β
cos(α + β) = cos α cos β − sin α sin β
cos(α − β) = cos α cos β + sin α sin β
The Attempt at a Solution
I worked out the LHS which makes it
cos2α cos2β - sin2α sin2β=RHS
Then, I'm stuck, however, i tried to do what I think can work...But I don't think it's right.
From here I think it's wrong.
(cos2α - sin2 β) (cos2β + sin2α)=RHS
(cos2α - sin2 β) (1) =RHSS
My problem is can we use identity for items like cos2 a + sin2 B = 1?
the variable is not the same :/