The Triangles Cut Off by the Sides of the Orthic Triangle
Let ABC be a triangle. The triangle formed by the endpoints of the altitudes is called the orthic triangle of ABC.[more]
The triangles cut off by the sides of the orthic triangle are similar to the original triangle.[less]
See theorem 184 in N. Altshiller-Court, College Geometry, Mineola, NY: Dover, 2007 p. 97.