Simson line
In geometry, given a triangle ABC and a point P on its circumcircle, the three closest points to P on lines AB, AC, and BC are collinear.
The line through these points is the Simson line of P, named for Robert Simson: the concept was first published, however, by William Wallace in 1797
http://en.wikipedia.org/wiki/Simson_line
http://www.mathcurve.com/courbes2d/deltoid/deltoid.shtml