[SOLVED] Finding sine and cosine formulas 1. The problem statement, all variables and given/known data If sinx/siny = 1/2 and cosx/cosy = 3 prove: sin (x + y) = 7/3 sinx cosx 2. Relevant equations sin (x + y) = sinx cosy = cosx siny 3. The attempt at a solution Can someone please give me a hint so that I can start? Thanks.