Persons

Mathematicians, geometers, and researchers referenced in the seelig archive and synthetic derivations.

Euclid of Alexandria (fl. 300 BCE)

Greek mathematician and author of the Elements, whose compass-and-straightedge propositions underpin the constructive foundations of every topic in this codex.

Pappus of Alexandria (c. 290–c. 350 CE)

Hellenistic mathematician whose Synagoge (Collection) preserved projective invariants, harmonic cross-ratios, and Stewart’s theorem precursors.

Heron of Alexandria (c. 10–c. 70 CE)

Greek mathematician and engineer who gave the classical proof of Heron’s formula for the area of a triangle in terms of its side lengths.

Menelaus of Alexandria (c. 70–140 CE)

Greek mathematician and astronomer who formulated Menelaus’s theorem for collinearity on a triangle’s sidelines.

Nathan Altshiller-Court (1881–1968)

Author of College Geometry: An Introduction to the Modern Geometry of the Triangle and the Circle, heavily referenced in Seelig’s harmonic and similitude derivations.

Lazare Carnot (1753–1823)

French mathematician and engineer whose Géométrie de position (1803) introduced signed geometric quantities and Carnot’s theorem.

Giovanni Ceva (1647–1734)

Italian mathematician who published De lineis rectis (1678), establishing Ceva’s theorem for concurrent cevians in a triangle.

John Horton Conway (1937–2020)

English mathematician who introduced Conway triangle notation (S, S_A, S_B, S_C, S_omega), extensively adopted by Fred Seelig throughout his notebooks.

H. S. M. Coxeter (1907–2003)

Geometer and co-author of Geometry Revisited, frequently cited in the notebooks for coaxial circles, inversion, and projective geometry.

Jean le Rond d’Alembert (1717–1783)

French mathematician and physicist associated with d’Alembert’s theorem on the collinearity of external and internal centers of similitude of three circles (Monge–d’Alembert theorem).

Heinrich Dörrie (1873–1955)

German mathematician and author of 100 Great Problems of Elementary Mathematics, cited by Seelig in his study of the Problem of Apollonius.

Leonhard Euler (1707–1783)

Swiss mathematician who proved the collinearity of the orthocenter, centroid, nine-point center, and circumcenter (the Euler line) and the distance formula d^2 = R(R - 2r) between incenter and circumcenter.

Giovanni Francesco Fagnano (1715–1797)

Italian mathematician who proved in 1775 that the orthic triangle minimizes perimeter among all triangles inscribed in an acute triangle.

Pierre de Fermat (1607–1665)

French mathematician who posed the problem of finding the point minimizing the sum of distances to the three vertices of a triangle.

Karl Wilhelm Feuerbach (1800–1834)

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

Clark Kimberling (b. 1942)

American mathematician and creator of the Encyclopedia of Triangle Centers (ETC), whose X(n) indexing links directly to Seelig’s triangle studies.

George Markowski (Contemporary)

Mathematician examined in Seelig’s Topic 32 notebook for the circumcircle midpoint-sagitta theorem J*K*L = (1/2)*r^2*R = (R^2 - d_IO^2)^2 / (8R).

Isaac Newton (1642–1727)

English mathematician and physicist whose Universal Arithmetick established algebraic triangle relations such as c = s - K/s for right triangles.

C. Stanley Ogilvy (1913–2000)

American mathematician and author of Excursions in Geometry (1969), frequently cited by Fred Seelig for coaxial circles, harmonic division, and orthogonal circle inversion.

Apollonius of Perga (c. 240–c. 190 BCE)

Greek geometer known as ‘The Great Geometer’, author of Conics and discoverer of the Apollonian circles of constant distance ratio.

Jean-Victor Poncelet (1788–1867)

French mathematician and founder of modern projective geometry, developing pole-polar duality, harmonic ranges, and coaxial pencils.

Claudius Ptolemy (c. 100–c. 170 CE)

Alexandrian astronomer and mathematician whose Almagest established Ptolemy’s theorem on the diagonals and sides of a cyclic quadrilateral.

Fred W. Seelig (20th–21st c.)

Independent geometric researcher and compiler of the 55 notebooks and computational spreadsheets forming the GEOMETOR Fundamentals archive. His investigations bridge classical synthetic geometry, Conway triangle notation, homogeneous barycentric coordinates, and exact algebraic verification.

Jakob Steiner (1796–1863)

Swiss geometer who systematized the power of a point, radical axes, and synthetic projective constructions.

Matthew Stewart (1717–1785)

Scottish mathematician who published Stewart’s theorem in Some General Theorems of Considerable Use in the Higher Parts of Mathematics (1746).

Evangelista Torricelli (1608–1647)

Italian physicist and mathematician who gave the classical equilateral-triangle circumcircle construction for the Fermat–Torricelli point X(13).

Paul Yiu (Contemporary)

Mathematician and author of Introduction to the Geometry of the Triangle, a primary reference in Fred Seelig’s notes on homogeneous barycentric coordinates.