Find the values of x on the interval [-π, π] where the tangent line to the graph of y = sin (x) cos (x) is horizontal. (Enter your answers as a comma-separated list.)

A trig identity is asinucosu = a/2 sin (2u) So you can write your equation as y=sin (x) cos (x) = 1/2 sin (2x) Use the crain rule here y′ = d / dx 1/2 sin (2x) = 1/2 cos (2x) d / dx 2x=cos (2x) The curve will have horizontal tangents when y' = 0. y′ = 0=cos (2x) On the interval [-pi, pi], solution to that is x=± π4,± 3π 4