1. The problem statement, all variables and given/known data Differentiate the identity sin2x = 2sinxcosx to develop the identity for cos2x, in terms on sin x and cos x 2. Relevant equations 3. The attempt at a solution Im not sure where to start with this one. Should I find the derivative of both sides of the equation, and then where do I go from there? The right side of that equation is 2cos^2x + sin^2x but im not sure how I can use that. Your help is appreciated as always!