Question

For what value of x does the graph of f have a horizontal tangent? f(x) = 2 sin(x) + sin^2 (x)

Answer 1

Sounds like a job for a 1st Derivative. What do you get for f'(x)?

Answer 2

er f'(x) = 2cos x + 2sin *cos x

Answer 3

Where does f'(x) take on the value zero (0)?