In a circle with radius $8.4 \,cm ,$ two radii are perpendicular to each other. The area of the minor sector formed by these radii is $\ldots \ldots \ldots cm ^{2}$.

In a circle with radius $14 \,cm ,$ the area of minor sector corresponding to minor $\widehat{ ACB }$ is $77 \,cm ^{2}$. Then, minor $\widehat{ ACB }$ subtends an angle of measure $\ldots \ldots \ldots \ldots$ at the centre.

Find the area of the shaded region in $Fig.$ where arcs drawn with centres $A , B , C$ and $D$ intersect in pairs at mid-points $P , Q , R$ and $S$ of the sides $AB , BC,$ $CD$ and $DA ,$ respectively of a square $ABCD$ (Use $\pi=3.14)$ (in $cm ^{2}$)

In $\odot( O , r),$ the length of minor $\widehat{ ACB }$ is one-eighth of the circumference of the circle. Then, the measure of the angle subtended at the centre by that arc is $\ldots \ldots \ldots \ldots$

The diameter of a circle with area $38.5\,m ^{2}$ is $\ldots \ldots \ldots \ldots m$.

The maximum area of a triangle inscribed in a semicircle having radius $10\,cm$ is $\ldots \ldots \ldots . . cm ^{2} .$