Index Nominum (Geometers & Contributors)

Biographical register of classical geometers and modern contributors referenced across the Encyclopedia of Triangle Centers.

Henri Brocard (1845–1922)

French mathematician and co-founder of modern triangle geometry; namesake of the Brocard points, Brocard angle ω, Brocard axis, Brocard circle, and Brocard triangles.

John Horton Conway (1937–2020)

Mathematician who introduced Conway triangle notation (S, S_A, S_B, S_C, S_ω) and the Conway circle in triangle geometry.

Jean-Gaston Darboux (1842–1917)

French geometer after whom the Darboux cubic (K004) and Darboux point X₂₀ (with De Longchamps) are named.

Leonhard Euler (1707–1783)

Swiss mathematician who proved in 1765 that the orthocenter X₄, circumcenter X₃, centroid X₂, and nine-point center X₅ are collinear on the Euler line.

Pierre de Fermat (1607–1665)

French mathematician who posed the problem of finding the point X₁₃ minimizing the sum of distances |AX| + |BX| + |CX| to the vertices of ABC.

Karl Wilhelm Feuerbach (1800–1834)

German geometer who proved in 1822 that the nine-point circle is tangent to the incircle at the Feuerbach point X₁₁ and to the three excircles.

Joseph Diaz Gergonne (1771–1859)

French geometer after whom the Gergonne point X₇ (perspector of the intouch triangle) and Gergonne line are named.

Bernard Gibert (fl. 1998–present)

Creator of Cubics in the Triangle Plane (CTC), cataloging and analyzing over 1,200 triangle cubics (K001–K1200+) referenced throughout the ETC.

Ernst Wilhelm Grebe (1804–1874)

German mathematician who investigated the symmedian point X₆ (Grebe point) in 1847.

Darij Grinberg (b. 1988)

Mathematician and early contributor to Hyacinthos and the ETC on barycentric coordinates, pedal triangles, and circle power identities.

Antreas P. Hatzipolakis (fl. 1998–present)

Founder of the Hyacinthos, Anopolis, and Euclid geometry research forums; proposer of hundreds of geometric configurations in the ETC.

Douglas Richard Hofstadter (b. 1945)

Cognitive scientist and geometer who discovered the Hofstadter points, including the Hofstadter zero point X₃₅₉ and one point X₃₆₀.

Randy Hutson (fl. 2011–present)

Prolific contributor to the ETC, specializing in synthetic constructions, perspective triangles, radical centers, and conjugate relationships.

Clark Kimberling (b. 1942)

Mathematician at the University of Evansville; founder and creator of the Encyclopedia of Triangle Centers (ETC).

Dasari Naga Vijay Krishna (fl. 2018–present)

Indian mathematician contributing synthetic reflection and circle constructions in the ETC.

Floor van Lamoen (b. 1966)

Dutch mathematician and triangle geometer, discoverer of the van Lamoen circle and numerous cevapoint and perspectivity constructions in the ETC.

Émile Michel Hyacinthe Lemoine (1840–1912)

French mathematician and co-founder of modern triangle geometry; studied the symmedian point X₆ (Lemoine point) and Lemoine circles.

Gaston Albert Gohier de Longchamps (1842–1906)

French mathematician who studied the De Longchamps point X₂₀ (reflection of the orthocenter in the circumcenter) and De Longchamps line.

César Eliud Lozada (fl. 2012–present)

Author of the Extended Glossary, Alphabetical Index of Terms, and Index of Triangles Referenced in ETC; contributor of thousands of triangle centers.

Angel Montesdeoca (fl. 2010–present)

Spanish geometer and contributor of numerous triangle centers, perspectors, and conic constructions in the ETC.

Peter J. C. Moses (fl. 2000–present)

Computational geometer and principal collaborator on the ETC, discoverer of thousands of barycentric combinations, coordinates, and circle/cubic properties.

Christian Heinrich von Nagel (1803–1882)

German geometer who studied the Nagel point X₈ (perspector of the extouch triangle) and Nagel line in 1836.

Joseph Jean Baptiste Neuberg (1840–1926)

Luxembourger-Belgian mathematician, co-founder of modern triangle geometry, discoverer of the Neuberg cubic (K001) and Neuberg circles.

Dao Thanh Oai (fl. 2013–present)

Geometer and discoverer of generalizations of the Simson line, Napoleon configuration, and perspective triangles in the ETC.

Cyril F. Parry (1915–1999)

British geometer who discovered the Parry point X₁₁₁, the Parry circle, and the Parry reflection property.

Stanley Rabinowitz (b. 1947)

Mathematician and author of ‘Location of Triangle Centers Relative to the Incircle and Circumcircle’ in the ETC.

Dan Reznik (fl. 2018–present)

Researcher on Poncelet porisms, locus invariants, and dynamic triangle center loci in the ETC.

Kiminari Shinagawa (fl. 2015–present)

Geometer who introduced the Shinagawa coefficients \((G, H) for triangle centers on the Euler line\).

Theodor Spieker (1823–1913)

German geometer who discovered the Spieker center X₁₀ (incenter of the medial triangle and center of mass of the perimeter of ABC).

Evangelista Torricelli (1608–1647)

Italian physicist and mathematician who solved Fermat’s problem via equilateral triangles erected on the sides of ABC, locating X₁₃ and X₁₄.

Eric W. Weisstein (b. 1969)

Creator of MathWorld, providing extensive cross-linked articles and illustrations for triangle centers and central circles.

Peter Yff (1924–2016)

Geometer who discovered the Yff center of congruence X₁₇₄, Yff parabolic point X₁₉₀, and Yff central triangles.

Paul Yiu (b. 1952)

Professor of Mathematics at Florida Atlantic University, founder of Forum Geometricorum, and pioneer of modern barycentric triangle geometry.