Application Of Derivatives

The point $x = 0$ is a point of local maxima of $f$

The point $x = 0$ is a point of local minima of $f$

Number of points of local maxima of $f$ in the interval $[\pi, 6\pi]$ is 3

Number of points of local minima of $f$ in the interval $[2\pi, 4\pi]$ is 1