The circles of Lester, Evans, Parry, and their generalizations - Paul Yiu Beginning with the famous Lester circle containing the circumcenter,...
Characterizations of bicentric quadrilaterals - Martin Josefsson We will prove two conditions for a tangential quadrilateral to be cyclic....
On the Euler reflection point - Cosmin Pohoata The Euler reflection point E of a triangle is known in literature as the common point of the...
Integer triangles with R/r = N - Allan MacLeod We consider the problem of finding integer-sided triangles with $R/r$ an integer, where R and r...
Construction with inscribed ellipses in a triangle - Nikolaos Dergiades We give a simple construction of the axes and foci of an inscribed...
Trilinear distance inequalities for the symmedian point, the centroid, and other triangle centers - Clark Kimberling Seven inequalities which...
Generalized Fibonacci circle chains - Giovanni Lucca We consider a particular circle chain where, each circle belonging to it, is tangent to the...
Calculations concerning the tangent lengths and tangency chords of a tangential quadrilateral - Martin Josefsson We derive formulas for the...
Iterates of Brocardian points and lines - Gotthard Weise We establish some interesting results on Brocardians in relation to the Steiner ellipses...
Three maximal cyclic quadrangles - Paris Pamfilos We study three problems concerning the determination of the maximal cyclic quadrangle under...
Diophantine Steiner triples and Pythagorean-type triangles - Bojan Hvala We present a connection between Diophantine Steiner triples (integer...
Orthic quadrilaterals of a convex quadrilateral - Maria Flavia Mammana, Biagio Micale and Mario Pennisi We introduce the orthic quadrilaterals of...
Simple relations regarding the Steiner inellipse of a triangle - Benedetto Scimemi By applying analytic geometry within a special Cartesian...
Conics tangent at the vertices to two sides of a triangle - Nikolaos Dergiades We study conics tangent to two sides of a given triangle at two...
Some triangle centers associated with the circles tangent to the excircles - Boris Odehnal We study those tritangent circles of the excircles of...
On the inradius of a tangential quadrilateral - Martin Josefsson We give a survey of known formulas for the inradius r of a tangential...
A maximal parallelogram characterization of ovals having circles as orthoptic curves - Nicolae Anghel It is shown that ovals admitting circles as...
The Poncelet pencil of rectangular hyperbolas - Roger C. Alperin We describe a pencil of rectangular hyperbolas depending on a triangle and the...
A new proof of a hard but important Sangaku problem - J. Marshall Unger We present a solution to a well-known sangaku problem, previously solved...
A triad of similar triangles associated with the perpendicular bisectors of the sides of a triangle - Quang Tuan Bui We prove some perspectivity...
