$\tan \theta=p \text { হলে, } \cos 2 \theta=\text { কত? }$

$4 \sin 7 \frac{1}{2}^{\circ} \cos 7 \frac{1}{2}^{\circ} \cos 15^{\circ}=$ কত?

$|\tan\theta+\sec\theta|=|\tan\theta|+|\sec\theta|, 0\leq \theta \leq 2\pi$ is possible only if-