1. The problem statement, all variables and given/known data A and B are two unit vectors in the x-y plane. A = <cos(a), sin(a)> B = <cos(b), sin(b)> I need to derive the trig identity: sin(a-b) = sin(a) cos(b) - sin(b) cos (a) I'm told to do it using the properties of the cross product A x B 2. Relevant equations A x B = |A||B| sinθ , where θ is the angle between the two vectors 3. The attempt at a solution Well, |A|=|B|=1 *unit vectors sinθ = sin(a-b) *for a > b A x B = cos(a)sin(b) - cos(b)sin(a) Putting this together, I get: sin(a-b) = cos(a)sin(b) - cos(b)sin(a) I can't figure out what I did wrong?