
05882841
j
2011f.00489
Josefsson, Martin
More characterizations of tangential quadrilaterals.
Forum Geom. 11, 6582 (2011).
2011
Florida Atlantic University, Department of Mathematical Sciences, Boca Raton, FL
EN
G40
tangential quadrilateral
incircle
http://forumgeom.fau.edu/FG2011volume11/FG201108index.html
A quadrilateral is said to be $tangential$ if there exists a circle tangent to its four sides. In this survey paper many proofs of not widely known characterizations of tangential quadrilaterals are given. Some characterizations involve only the lengths of the sides of the quadrilateral, while the most sophisticated ones involve even the radii of excircles defined by the sides and diagonals of the quadrilateral. The paper is wellwritten and is very interesting. It will make a good read even for undergraduates interested in elementary euclidean geometry.
Antonio M. Oller (Zaragoza)