A’= A(cosx)^2 + 2Bcosxsinx + C(sinx)^2
C’= A(sinx)^2 – 2Bcosxsinx + C(cosx)^2
I need to prove that (A’)(C’) is equal to AC – B^2
If tried multiplying both together but I cant seem to find the right trig identities or how to simplify it.
any steps or hints would be Great