Definition:Concyclic Points

A set of points $$S = \left\{{P_1, P_2, \ldots, P_n}\right\}$$ is concyclic if they all lie on the circumference of a circle.


 * Concyclic.png

In the above diagram, points $$B, C, D, E$$ are concyclic, as they all lie on the circumference of the circle centered at $$A$$.