Therefore the area of the circle is 31416 inches squared. What is the area of this rectangle. Area ½ r 2 th r radius th angle in radians.
A 12 p r 2.
For a semi circle this is always 180 degrees Area of a semi circle definition. The formula the calculator uses is as follows. The area of a semicircle is half the area area of the circle from which it is made. It is interesting to compare the area of a circle to a square.