Four enclosed arcs produced with the same radius are inscribed in such a way, as shown in the image below.
What percentage of area is the green area, compared to the square, when s = 10?
s divided by the square root of 2 will give you the radius of the circle.
s / sqrt(2) = 10 / sqrt(2) = 5·sqrt(2)
The area of the (full) circle will be: pi · [ 5·sqrt(2) ]2 = 50·pi
The area of the square = 100
---> the area of the green portion = [ ( 50·pi ) - ( 100 ) ] / 2 = 25·pi - 50