Dear milan,

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.