Constructions of tangent circles in the hyperbolic disk, interpreted in Euclidean geometry, give us examples of four mutually tangent circles. These are shown to satisfy Descartes's Theorem for tangent circles. We also show that the Archimedes twin circles in the hyperbolic arbelos are usually not hyperbolic congruent, even though they are Euclidean congruent. We include a few construction instructions because all items under consideration require surprisingly few steps.
Prof. Mike McDaniel, Professor of Mathematics, Aquinas College
"Tangent circles in the hyperbolic disk,"
Rose-Hulman Undergraduate Mathematics Journal: Vol. 14
, Article 2.
Available at: http://scholar.rose-hulman.edu/rhumj/vol14/iss1/2