1. The problem statement, all variables and given/known data Proof that (1/6)sin(3x)-(1/18)sin(9x) = (2/9)sin^3(3x) 2. Relevant equations 3. The attempt at a solution I am just curious exactly how the power on the sine function is cubic on one side. It obviously has to do with something that increases the power on the sin(9x) function after it becomes a sin(3x). In other words, higher multiple angles somehow increase the trig power and I am not exactly sure how or what formula I should use to prove their equality.