Oldknow Points

The Perspective Centers of a triangle and the Tangential Triangles of its inner and outer Soddy Circles, given by

$${\it Ol}=I+2{\it Ge}$$

$${\it Ol'}=I-2{\it Ge},$$

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

See also Gergonne Point, Incenter, Perspective Center, Soddy Circles, Tangential Triangle

References

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