===> sin^2A-sin^2Asin^2 B-sin^2B+sin^2Asin^2B
sin(A+B)sin(A-B) = sin^2A-sin^2B is what I have to prove
This is obviously a quadratic. I just don't know how it would multiply
e.g sinAcosB x sinAcosB = ???
sin(x) = cos(90- x) and cos(x) = sin(90 - x)
let x = A + B,
then i can write this
cos(A-B) =cos(A)cos(B) + sin(A)sin(B)
i think these prooves can help you...