Amy Bell, Hansen's right triangle theorem, its converse and
Forum Geometricorum, 6 (2006) 335--342.
Abstract: We generalize D. W. Hansen's theorem relating the inradius and
exradii of a right triangle and its sides to an arbitrary triangle. Specifically,
given a triangle, we find two quadruples of segments with equal sums and
equal sums of squares. A strong converse of Hansen's theorem is also established.