Update v3 (April 2026): The H-O-H bond angle result cos (θHOH) = −1/4, giving θ = 104. 4775° (deviation 0. 027° from experiment), is now established as an exact algebraic identity via the Lucas number L₃. Article 14 proves that φ³ − φ⁻³ = L₃ = 4 exactly, so cos (θHOH) = −1/L₃ = −1/4 is a consequence of the Hopf torus topology at level n=3, not a numerical coincidence. This closes PO-H2O-1 for the cosine value A. All original results of v2 are preserved. MSC: 81V55 · 81Q05 · 92E10 PACS: 31. 10. +z · 31. 15. -p · 33. 15. Dj · 31. 25. -v
Michel ALdon (Wed,) studied this question.