On some triads of homothetic triangles - Gotthard Weise To a given reference triangle and three directions, we construct four triads of...
Two pairs of Archimedean circles in the arbelos - Dao Thanh Oai We construct four circles congruent to the Archimedean twin circles in the...
The Cevian Simson transformation - Bernard Gibert We study a transformation whose origin lies in the relation between concurrent Simson lines...
Asymptotic directions of pivotal isocubics - Bernard Gibert Given the pivotal isocubic K = p(Omega,P), we seek all the other isocubics K_1 =...
Antirhombi - Nikolaos Dergiades First we give the definition and some properties of the non-rhombus quadrilateral that we call antirhombus, that...
A note on reflections - Emmanuel Antonio Jose Garcia We prove some simple results associated with the triangle formed by the reflections of a...
The Miquel points, pseudocircumcenter, and Euler-Poncelet point of a complete quadrilateral - Michal Rolinek and Le Anh Dung We prove over 40...
Properties of equidiagonal quadrilaterals - Martin Josefsson We prove eight necessary and sufficient conditions for a convex quadrilateral to...
A note on the Fermat-Torricelli point of a class of polygons - Cristinel Mortici The aim of this note is to prove a result related to the...
A simple proof of Gibert's generalization of the Lester circle theorem - Dao Thanh Oai We give a simple proof of Gibert's generalization of the...
On a geometric locus in taxicab geometry - Bryan Brzycki In axiomatic geometry, the taxicab model of geometry is important as an example of a...
Inversions in an ellipse - José L. Ramírez In this paper we study the inversion in an ellipse which generalizes the classical inversion with...
Semi-similar complete quadrangles - Benedetto Scimemi Let A = A_1A_2A_3A_4 and B =B_1B_2B_3B_4 be complete quadrangles and assume that each side...
The touchpoints triangles and the Feuerbach hyperbolas - Sándor N. Kiss and Paul Yiu In this paper we generalize the famous Kariya theorem on the...
Distances between the circumcenter of the extouch triangle and the classical centers - Marie-Nicole Gras We compute, in a triangle, the distances...
Kitta's double-locked problem - J. Marshall Unger I present strongly contrasting solutions of a remarkable sangaku. The general solution...
Dynamics of the nested triangles formed by the tops of the perpendicular bisectors - Grégoire Nicollier Given a triangle, we construct a new...
The associated harmonic quadrilateral - Paris Pamfilos In this article we study a natural association of a harmonic quadrilateral to every...
Angle and circle characterizations of tangential quadrilaterals - Martin Josefsson We prove five necessary and sufficient conditions for a convex...
A vector-based proof of Morley's trisector theorem - Cesare Donolato A proof is given of Morley's trisector theorem using elementary vector...
