id: 05882841
dt: j
an: 2011f.00489
au: Josefsson, Martin
ti: More characterizations of tangential quadrilaterals.
so: Forum Geom. 11, 65-82 (2011).
py: 2011
pu: Florida Atlantic University, Department of Mathematical Sciences, Boca
Raton, FL
la: EN
cc: G40
ut: tangential quadrilateral; incircle
ci:
li: http://forumgeom.fau.edu/FG2011volume11/FG201108index.html
ab: 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 well-written and is very interesting. It will make a good
read even for undergraduates interested in elementary euclidean
geometry.
rv: Antonio M. Oller (Zaragoza)