What is the area (in $cm^2$) of a square inscribed in a circle of radius $8 \, cm$?

In a circle with radius $21 \ cm$,the perimeter of a minor sector is $64 \ cm$. Then,the length of the arc of that sector is $\ldots \ cm$.

If the length of an arc of a circle of radius $r$ is equal to that of an arc of a circle of radius $2r$,then the angle of the corresponding sector of the first circle is double the angle of the corresponding sector of the other circle. Is this statement false? Why?

In a circle with radius $30\,cm$,a minor arc subtends an angle of measure $60^{\circ}$ at the centre. Then,the area of the minor sector formed by that arc is $\ldots \ldots \ldots \ldots$ $cm^{2}$. $(\pi = 3.14)$

$A$ cow is tied with a rope of length $14 \, m$ at the corner of a rectangular field of dimensions $20 \, m \times 16 \, m$. Find the area of the field in which the cow can graze. (in $m^2$)

$\overline{ OA }$ and $\overline{ OB }$ are radii of a circle perpendicular to each other. If $OA = 5.6 \, cm$,then the area of the minor sector formed by those radii is .......... $cm^2$.