The value of $\sin \dfrac {2\pi}{7}+\sin \dfrac {4\pi}{7}+\sin \dfrac {8\pi}{7}$ is

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

$\frac{1+\tan 25^{\circ}}{1-\tan 25^{\circ}}=$ কত?

দৃশ্যকল্প-১: $f(\theta)=\frac{1+\cos ^{2} \theta}{\cos \theta}$

দৃশ্যকল্প-২: $\mathrm{g}(\mathrm{x})=\cos \mathrm{x}$.

sin18° এর মান কত?