Gergonne Line
The perspective line for the Contact Triangle 
and itsTangential Triangle 
. It is determined by the Nobbs Points 
, 
, and 
. In addition tothe Nobbs Points, the Fletcher Point and Evans Point also lie on the Gergonne line where itintersects 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
See also Contact Triangle, Euler Line, Evans Point, Fletcher Point,Nobbs Points, Soddy Line, Tangential Triangle
References
Oldknow, A. ``The Euler-Gergonne-Soddy Triangle of a Triangle.'' Amer. Math. Monthly 103, 319-329, 1996.
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