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Stephen Tellman and David Lovelock
Department of Mathematics
University of Arizona
Tucson, Arizona 85721

This program allows you to experiment with the size of a triangle and see the resulting incircles, excircles, circumcircles and nine-point circles. It is designed to give a pictorial representation of Feuerbach's Theorem which states that the nine-point circle of a triangle T passes through the following nine points: the midpoints of each side of T, the foot of each altitude of T and the Euler points of T. Furthermore, the nine-point circle of T is tangent to the inscribed circle of T and the three exscribed circles of T.

Download [202 KB].

Look at other programs in the University of Arizona collection.