3.10 Application of integrals

1.

(a) $4$ (b) $\displaystyle{\frac{3\pi}{16}}$

2.

(a) $\displaystyle{4\pi^2}$ (b) $\displaystyle{5\pi^2}$

3.

(a) $6$ (b) $\displaystyle{\frac{1}{6}}$ (c) $\displaystyle{\frac{3\pi}{2}}$