-- The point (3, 0) is on the circle.
-- So the distance to it from the center of the circle
must be the radius of the circle.
-- The center of THIS circle is at the origin.
-- The distance from the origin to (3, 0) is 3 .
-- The radius of this circle is 3 .
-- The area of any circle is (pi) (radius of the circle)²
-- The area of THIS circle is (pi) (3)² = 9 pi = 28.27 (rounded)
