$\int_{0}^{1} \frac{dx}{1 + x^{2}} = ?$

$\int_{0}^{\frac{\pi}{4}} \frac{\cos \theta}{\cos ^{2} \theta} d \theta=?$

The value of $\displaystyle\int^{199\pi/2}_{-\pi/2}\sqrt{(1+\cos 2x)}dx$ is?

$\int_{0}^{\pi / 2} \cos x d x=\text { কত? }$

$\int_{0}^{\frac{\pi}{6}} \sin ^{2} x \cos x d x=$ কত ?