1. The problem statement, all variables and given/known data sin4x-sin2x/sin2x=cos3x/cosx 2. Relevant equations sin2x = 2sinxcosx 3. The attempt at a solution LS = sin(2x + 2x) - sin2x/sin2x = sin2xcos2x + cos2xsin2x - sin2x/sin2x = 2sin2xcos2x - sin2x/sin2x This is where i get stuck... I don't know what happens if you try to: 2sinx2x - sin2x or 2sin2x/sin2x, is that possible or not? Can you guys help me solve this question? Thanks.