3. Triangle and Inscribed Angle  (07/06/25) Not constant, Absolute unit length (1)  4. Model  Make a disk model, Open and closed  5. Disk and Hyperboloid  Interchangeable relations  6. Equivalent Deformation,     Comparison with Elliptic Geometry (1)  (07/04/14) Locus of vertex of a triangle  7. Parallel Angle  What is it?  8. Lobachevsky's Postulate  (07/07/19) How was it found? Can we draw infinity?  9. Distance and Angle, Hyperbolic Trigonomery  (07/06/22) Dependent relations, Absolute unit length (2) 10. Equidistant Lines (1)  How does it look?  Parallel curves 11. Ultraparallel Lines  Common perpendicular 12. Tiling (tessellation)  (07/05/01) Reflection, Ideal triangle 13. Parallel Translation (1)  Get locus by reflection 14. Circle  Cutting hemisphere 15. Move Circle  Toward infinity 16. Extending Disk Model   (07/07/02) To get real hyperbolic plane 17. Horocycle (1)  Hemisphere, Translation, Equidistant lines (2) 18. Pseudo-sphere (1)  Is hyperbolic surface realized? 19. Upper Half-plane (1)  Relation with Poincare's disk, Digitized model 20. Horocycle (2)  Poincare's disk, Upper Half-plane (2) 21. Metric, Break Pythagorean Theorem  (07/06/13) Riemann, Mercator, Pseudo-sphere (2) 22. Mutual Relations among Models  Ray and chain 5 models 23. Curvature (1)  Osculating circle, Curvature of pseudosphere (1) 24. Curvature (2)  What happens if curvature changes? 25. Gauss-Bonnet Theorem  Curvature of pseudosphere (2) 26. Touchable Model  (07/06/20) Paper craft of true hyperbolic plane 27. H(+) Plane and Euclidean Plane  Visual comparison under unchanged length 28. Analytic Curve   Lambert's quardrangle 29. Hyperbolic Function  Source, Hyperbolic angle, Definition of logarithm 30. Inversion and Infinity (under construction)   What is the end of hyperbola? 31. Upper Half-plane (4) (under construction)   Can we come to Eucledean plane without jump? 32. Right Angled Polygon  (07/03/29) Infinite polygon 33. Dodecahedron  3-D tiling 34. Ideal Tetrahedron  3-D tiling