A Line Associated with an Excircle
An excircle is a circle drawn outside a triangle that is tangent to the extensions of two of its sides and to the third side.[more]
Let ABC be a triangle. Then these three points are collinear: (1) the point of tangency of the excircle opposite A, (2) the incenter of ABC, and (3) the midpoint of the altitude of ABC from A.[less]
See problem 5 in Classical Theorems in Plane Geometry.