Sol. $3 \cos ^4 \theta-5 \cos ^2 \theta-2 \sin ^6 \theta+2=0$

$\Rightarrow \quad 3 \cos ^4 \theta-3 \cos ^2 \theta-2 \cos ^2 \theta-2 \sin ^6 \theta+2=0$

$\Rightarrow \quad 3 \cos ^4 \theta-3 \cos ^2 \theta+2 \sin ^2 \theta-2 \sin ^6 \theta=0$

$\Rightarrow \quad 3 \cos ^2 \theta\left(\cos ^2 \theta-1\right)+2 \sin ^2 \theta\left(\sin ^4 \theta-1\right)=0$

$\Rightarrow \quad-3 \cos ^2 \theta \sin ^2 \theta+2 \sin ^2 \theta\left(1+\sin ^2 \theta\right) \cos ^2 \theta-1$

$\Rightarrow \quad \sin ^2 \theta \cos ^2 \theta\left(2+2 \sin ^2 \theta-3\right)=0$

$\Rightarrow \quad \sin ^2 \theta \cos ^2 \theta\left(2 \sin ^2 \theta-1\right)=0$

$(C1)$ $\sin ^2 \theta=0 \rightarrow 3$ solution ; $\theta=\{0, \pi, 2 \pi\}$

$(C2)$ $\cos ^2 \theta=0 \rightarrow 2$ solution $; \theta=\left\{\frac{\pi}{2}, \frac{3 \pi}{2}\right\}$

(C) $\sin ^2 \theta=\frac{1}{2} \rightarrow 4$ solution; $\theta=\left\{\frac{\pi}{4}, \frac{3 \pi}{4}, \frac{5 \pi}{4}, \frac{7 \pi}{4}\right\}$

No. of solution $=9$