9. In Fig, AB and CD are two diameters of a circle (with centre O) perpendicular to each other and OD is the diameter of the smaller circle. If OA = 7 cm, find the area of the shaded region.
Firstly, the area of the smaller circle
Now, the area of
And, The area of the bigger semicircle
Hence the area of the shaded region
Therefore the area of the shaded region is 66.5 cm2.