1. The problem statement, all variables and given/known data I need to find ∫cos^2 x using cos x cos y = 1/2(cos(x+y)+cos(x-y)). Note that it is not cos to the power of 2x. It is cos to the power of 2 multiplied by x. 2. Relevant equations cos x cos y = 1/2(cos(x+y)+cos(x-y)) 3. The attempt at a solution I've searched my textbook and online everywhere, but my teacher hasn't given me any guidance. All I can think of is somehow converting cos x cos y = 1/2(cos(x+y)+cos(x-y)) to cos2x so I can then use a general formula/rule. Any help is highly appreciated.