Rigby Points

The Perspective Centers of the Tangential and Contact Triangles of the inner and outer Soddy Points. The Rigby points are given by

$${\it Ri}=I+{\textstyle{4\over 3}}{\it Ge}$$

$${\it Ri}'=I-{\textstyle{4\over 3}}{\it Ge},$$

where $I$ is the Incenter and Ge is the Gergonne Point.

See also Contact Triangle, Gergonne Point, Griffiths Points, Incenter, Oldknow Points, Soddy Points, Tangential Triangle

References

Oldknow, A. ``The Euler-Gergonne-Soddy Triangle of a Triangle.'' Amer. Math. Monthly 103, 319-329, 1996.