Research & Editorial Log

2026-11-12 — Initial Euler (1765) & Feuerbach (1822) Bilingual Book Codex (v0.1.0)

• Transcribed and translated Leonhard Euler’s Solutio facilis problematum quorumdam geometricorum difficillimorum (E325, 1765/1767, §§ 1–34, pp. 103–123) and Karl Wilhelm Feuerbach’s Eigenschaften einiger merkwürdigen Punkte des geradlinigen Dreiecks (1822, Vorrede pp. I–XVI, §§ 1–87, and synthetic Euclidean Anhang 1.–9. Satz, pp. 56–62) directly from archival scans.

• Proved 30 symbolic polynomial identities in sympy (prove_euler_1765_identities()), identifying and correcting Feuerbach’s § 51 sign slip (\(\overline{OS^{(k)}}^2 = 2r^{(k)2} - 2\rho R\)) and showing why the cancellation of \(\rho R\) in Apollonius’s median theorem preserved the exact truth of § 57 (Feuerbach’s Theorem).

• Implemented exact geometor.model compass-and-straightedge constructions on Heronian (15, 13, 14) yielding X(5) = (6, 63/16), X(11) = (6, 8), and Fea, Feb, Fec, with four theme-adaptive .euclid-graphic SVGs.