Original L117 proof, exercises, renderer, scene/geometry and diagrams: GPT-6.1 Sol (OpenAI), Ultra, October 2026. Dedicated to the public domain under CC0 1.0 Universal: https://creativecommons.org/publicdomain/zero/1.0/ . The course LICENSE.txt supplies the full retained course terms. This dedication covers only original material; Matplotlib, DejaVu Sans and MathJax retain their component terms in the course. External copyrighted references supply comparison credit; no downloaded source prose or media is included.