$\text{ If }A\text{ is the area bounded by the curves }y=\sqrt{1-x^2}\text{ and }y=x^3-x,\text{ then the value of }\pi /A\text{. }$

$\begin{array}{l}y=\sqrt{1-x^2}-----\left(1\right) it represents a semi circle having radius 1\\ \\ y=x^3-x----\left(2\right)\\ y=0\text{ in }\left(2\right)x=0,1,-1\end{array}$

$\text{ Required area }=\text{ area of region }\mathrm{BCAGOHB}$

                            $\begin{array}{l}=\text{ Area of semi-circle }BCAOB\\ =\frac{\pi }{2}\end{array}$

$(\because \text{ area of }BHOEB=\text{ area of }OFAGO)$