How do you find an area of a sector of a circle?

That would certainly do it.

find out sector of a circle with figure

14 + 72 is not a prime number.

Divide the circumference by pi, and that will give you the diameter. Then take half of the diameter (the radius), and plug it into the formula for the area of a circle (A=πr²)

Find the area of the whole circle and divide by two. Area of semicircle = 0.5*pi*r2, where pi = 3.14159 and r is the radius