The perspective line for the Contact Triangle and its
Tangential Triangle . It is determined by the Nobbs Points , , and . In addition to
the Nobbs Points, the Fletcher Point and Evans Point also lie on the Gergonne line where it
intersects the Soddy Line and Euler Line, respectively.
The and coordinates are given by

so form a Harmonic Range. The equation of the Gergonne line is

**References**

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

© 1996-9

1999-05-25