How do you differentiate cos x all squared? - Answers

If this is a homework assignment, please consider trying to answer it yourself first, otherwise the value of the reinforcement of the lesson offered by the assignment will be lost on you.The deriviative d/dx cos2(x) can be evaluated using the product rule.Recall that d/dx f(x)g(x) = g(x) d/dx f(x) + f(x) d/dx g(x)In this case, both f(x) and g(x) are cos(x), and cos2x = cos(x)cos(x), so...d/dx cos(x)cos(x) = -cos(x)sin(x) - cos(x)sin(x) = -2sin(x)cos(x)