Editing Homogeneous coordinates (section)

==Circular points==
{{Main|Circular points at infinity}}
The homogeneous form for the equation of a circle in the real or complex projective plane is
{{nowrap|<math>x^2 + y^2 + 2axz + 2byz + cz^2 = 0</math>}}. The intersection of
this curve with the line at infinity can be found by setting {{nowrap|<math>z = 0</math>}}. This produces the equation
{{nowrap|<math>x^2 + y^2 = 0</math>}} which has two solutions over the complex numbers, giving rise to
the points with homogeneous coordinates {{nowrap|<math>(1, i, 0)</math>}} and {{nowrap|<math>(1, -i, 0)</math>}} in the complex projective
plane. These points are called the [[circular points at infinity]] and can be regarded as the common points of
intersection of all circles. This can be generalized to curves of higher order as [[circular algebraic curve]]s.<ref>
    {{harvnb|Jones|1912|p= 204}}</ref>