Application Of Derivatives

Strictly increasing on $\left(\frac{3 \pi}{8}, \frac{5 \pi}{8}\right)$

Strictly increasing on $\left(\frac{\pi}{8}, \frac{3 \pi}{8}\right)$

Strictly decreasing on $\left(\frac{3 \pi}{8}, \frac{5 \pi}{8}\right)$

${\text { Strictly decreasing on }}\left(\frac{\pi}{8}, \frac{5 \pi}{8}\right)$