 In this system, the points at infinity may be chosen as those whose "z"-coordinate is zero.The two circular points at infinity are two of these, usually taken to be those with homogeneous coordinates

A real circle, defined by its center point ("x"0,"y"0) and radius "r" (all three of which are real numbers) may be described as the set of real solutions to the equation
Converting this into a homogeneous equation and taking the set of all complex-number solutions gives the complexification of the circle.The two circular points have their name because they lie on the complexification of every real circle.