So since this is half a circle, we have to divide the area of a circle by 2. So that would give us 1/2 pi* r^2. We find the radius by dividing 10 by 2. So the radius is 5. Plugging that in for r in 1/2(pi)(r^2) we get 1/2(pi)(5^2) which is 25pi/2. Turning pi into 3.14 we have (25(3.14))/2 which is 78.5/2 which is approximately 39.25 units^2
