"The" Griffiths point Gr is the fixed point in Griffiths' theorem. Given four points on a circle and a line through the center of the circle, the four corresponding Griffiths points are collinear. Let the inner and outer Soddy triangles of a reference triangle Δ A B C be denoted Δ P Q R and Δ P' Q' R', respectively. Similarly, let the tangential triangles of Δ P Q R and Δ P' Q' R' be denoted Δ X Y Z and Δ X' Y' Z', respectively. Then the inner (respectively, outer) Griffiths point Gr (respectively, G r') is the perspector of Δ P Q R and Δ X' Y' Z' (respectively, Δ P' Q' R' and Δ X Y Z). The Griffiths points lie on the Soddy line.

first Eppstein point | Gergonne point | Griffiths' theorem | incenter | Rigby points | second Eppstein point | Soddy line | Soddy triangles