the equation of normal unit circle is:
x^2 + y^2 = 1.
The general circle can have other radius, can shift along x-axis and along y-axis, so the equation of general circle is:
(x-a)^2 + (y-b)^2 = r^2.
I suggest you that convert the original equation to such form and all will be happy.
I think sqrt(52) is false result.