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.
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