tan θ =  $\frac{3}{4}$   , π < θ <   $\frac{3 π}{2}$   হলে, cos 2θ  + sin 2θ  = ? 

$\begin{array}{l}\text { } \text { }^{\mathrm{}} \tan \theta=\frac{3}{4}, \pi<\theta<\frac{3 \pi}{2} \cdot \text { হলে } \\ \cos 2 \theta+\sin 2 \theta=\frac{2 \tan \theta}{1+\tan ^{2} \theta}+\frac{1-\tan ^{2} \theta}{1+\tan ^{2} \theta} \\ =\frac{1+2 \tan \theta-\tan ^{2} \theta}{1+\tan ^{2} \theta}=\frac{1+2 \times \frac{3}{4}-\frac{9}{16}}{1+\frac{9}{16}} \\ =\frac{\frac{16+24-9}{16}}{\frac{25}{16}}=\frac{31}{25} \text { }\end{array}$