Question

In a sector COD of a circle, centre O , in which angle COD =4/3 radians. The points A and B lie on the OD and OC respectively, and AB is an arc of a circle, centre O, of radius 7cm. Given that the area of the shaded region ABCD is 48cm^2. Find the perimeter of this shaded region.

I can't provide figure.

Answer 1

the area of a sector is a = 1/2 r^2 θ
so, the area of COD = 1/2 r^2 * 4/3
area of AOB = 1/2 * 7^2 * 4/3 = 98/3
Now, ABCD = COD - AOB = 2/3 r^2 - 98/3 = 48
Now you can find r, and finish up.

Answer 2

32 cm