The standard equation for a circle with center at (h,k) and radius r is
(x-h)^2 + (y-k)^2 = r^2, where (h,k) is the center of the circle.
The formula for the circumference of a circle is C = 2pi*r. In this particular problem, we need to determine the radius of the circle. That radius is: r = C/[2pi]. Here, C = 22pi, so we get r = 22pi/[2pi], and so r^2 = 11^2.
