康威圆与勒洛三角形:过六点的等宽曲线

康威圆与勒洛三角形:过六点的等宽曲线
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2020-04-12 21:32
① 本范例演示了康威圆(Conway circle)与勒洛三角形(Reuleaux triangle)的关联:康威圆经过三角形三边延长线上的六个特定点,而一个广义的勒洛三角形(等宽曲线)也恰好经过这六个点。② 核心数学概念包括:三角形内切圆、外接圆、等宽曲线、几何构造、旋转与对称。③ 作图要点:使用GeoGebra命令如Polygon(多边形)、Circle(圆)、Line(直线)、Intersect(交点)、Segment(线段)、CircleArc(圆弧)、Rotate(旋转)、Center(中心)、OrthogonalLine(垂线)等,构造了三角形ABC、内切圆c、以及通过旋转和圆弧生成的勒洛三角形,涉及对象包括anim、A、B、C、t1、c、a、b、d、e、f、g、h、i、D、E、F、G、H、I、j、k、l、m、n、p、q、r_1、s、t、c_1、d_1、e_1、f_1、g_1、r、h_1、r2、r3、a0。④ 适合高中及以上学段,用于几何构造、等宽曲线性质、以及动态数学探索,也可作为教师演示或学生自主探究的素材。

GeoGebra 命令及参数

  1. Polygon(A, B, C) → t1, c, a, b
  2. Circle(A, a) → d
  3. Circle(B, b) → e
  4. Circle(C, c) → f
  5. Line(A, B) → g
  6. Line(A, C) → h
  7. Line(C, B) → i
  8. Intersect(d, g, 1) → D
  9. Intersect(d, h, 1) → E
  10. Intersect(f, i, 1) → F
  11. Intersect(f, h, 2) → G
  12. Intersect(e, g, 2) → H
  13. Intersect(e, i, 2) → I
  14. Segment(C, B) → j
  15. Segment(A, D) → k
  16. Segment(A, E) → l
  17. Segment(B, A) → m
  18. Segment(C, F) → n
  19. Segment(C, G) → p
  20. Segment(A, C) → q
  21. Segment(B, I) → r_1
  22. Segment(B, H) → s
  23. Circle(D, E, I) → t
  24. CircleArc(A, E, D) → c_1
  25. CircleArc(A, G, H) → d_1
  26. CircleArc(B, D, F) → e_1
  27. CircleArc(C, F, G) → f_1
  28. CircleArc(B, H, I) → g_1
  29. Min(1, Max[anim - 1, 0]) → r
  30. CircleArc(C, I, E) → h_1
  31. Min(1, Max[anim - 2.2, 0]) → r2
  32. Min(1, Max[anim - 3.4, 0]) → r3
  33. Segment(E, G) → a0
  34. Rotate(E, (r * Angle[C, A, B]), A) → E'
  35. Rotate(G, (r * Angle[C, A, B]), A) → G'
  36. Segment(E', G') → a1
  37. Rotate(E', (r2 * Angle[A, B, C]), B) → E''
  38. Rotate(G', (r2 * Angle[A, B, C]), B) → G''
  39. Segment(E'', G'') → a2
  40. Rotate(E'', (r3 * Angle[B, C, A]), C) → E'''
  41. Rotate(G'', (r3 * Angle[B, C, A]), C) → G'''
  42. Segment(E''', G''') → a3
  43. Circle(E''', a) → k_1
  44. Circle(G''', b) → p_1
  45. Intersect(k_1, a4, 1) → J
  46. Intersect(p_1, a4, 1) → K
  47. Segment(E''', J) → i_1
  48. Segment(J, K) → j_1
  49. Segment(K, G''') → l_1
  50. CircleArc(A, E, E') → aa1
  51. CircleArc(A, G, G') → aa2
  52. CircleArc(B, D, E'') → aa3
  53. CircleArc(B, H, G'') → aa4
  54. CircleArc(C, F, E''') → aa5
  55. CircleArc(C, I, G''') → aa6
  56. Center(t) → L
  57. Min(1, Max[anim + 0.2, 0]) → r0
  58. Rotate(E, (r0 * 360°), L) → E'_1
  59. OrthogonalLine(L, g) → m_1
  60. Intersect(g, m_1) → M
  61. Circle(L, M) → q_1
  62. Segment(L, E'_1) → n_1
  63. Segment(L, E) → s_1
  64. Intersect(q_1, s_1) → N,
  65. Rotate(N, (r0 * 360°), L) → N'
  66. CircleArc(L, N, N') → ptc
  67. CircleArc(L, E, E'_1) → ptc2
  68. OrthogonalLine(G''', a4) → t_1
  69. OrthogonalLine(E''', a4) → a_1