梯形中位线（中位线段）动态演示：两条定理无字图解

GeoGebra 命令及参数

1. Line(A, B) → f
2. Ray(A, B) → g
3. Point(g) → C
4. Ray(A, C) → h
5. Segment(A, C) → i
6. Slope(f) → m
7. PointIn(a) → D
8. Segment(A, D) → j
9. Line(D, i) → k
10. Point(k) → E
11. Ray(D, E) → l
12. Point(l) → F
13. Ray(D, F) → n
14. Segment(F, C) → p
15. Segment(D, F) → q
16. Min(j, i) → c
17. Circle(A, (0.2 * c)) → d
18. Intersect(d, j, 1) → G
19. Intersect(d, i, 1) → H
20. CircleSector(A, H, G) → e
21. Angle(C, A, D) → α
22. CircleSector(A, G, H) → r
23. Dilate(A, If[0 < o ≤ 1, 1 - o, 0], C) → A'
24. Midpoint(D, A) → I
25. Midpoint(F, C) → J
26. Segment(A, A') → s
27. Dilate(F, If[0 < o ≤ 1, 1 - o, 0], D) → F'
28. Segment(F, F') → t
29. Dilate(A, If[1 < o ≤ 2, 2 - o, 0], D) → A'_1
30. Segment(A, A'_1) → f_1
31. Ray(A, D) → g_1
32. Point(g_1) → K
33. Ray(D, K) → h_1
34. Dilate(A, If[2 < o ≤ 3, 3 - o, 0], D) → A'_2
35. Vector(A, A'_2) → u
36. Translate(e, u) → e'
37. Dilate(A, If[3 < o ≤ 4, 4 - o, 0], I) → A'_3
38. Dilate(C, If[3 < o ≤ 4, 4 - o, 0], J) → C'
39. Segment(A, A'_3) → i_1
40. Segment(C, C') → j_1
41. Dilate(I, If[4 < o ≤ 5, 5 - o, 0], D) → I'
42. Dilate(J, If[4 < o ≤ 5, 5 - o, 0], F) → J'
43. Segment(I, I') → k_1
44. Segment(J, J') → l_1
45. Rotate(A, If[5 < o ≤ 6, ((o - 5) * π), π], I) → A'_4
46. Rotate(A'_3, If[5 < o ≤ 6, ((o - 5) * π), π], I) → L
47. Segment(A'_4, L) → m_1
48. Polygon(A, C, F, D) → poly1, a_1, c_1, f_2, d_1
49. Rotate(C, If[5 < o ≤ 6, ((-(o - 5)) * π), (-π)], J) → C'_1
50. Rotate(C', If[5 < o ≤ 6, ((-(o - 5)) * π), (-π)], J) → C''
51. Segment(C'_1, C'') → n_1
52. Dilate(I, If[6 < o ≤ 7, 7 - o, 0], J) → I'_1
53. Segment(I, I'_1) → p_1
54. Dilate(D, If[7 < o ≤ 8, 8 - o, 0], I) → D'
55. Vector(D, D') → v
56. Translate(e', v) → e''
57. Translate(r, u) → r'
58. Translate(r', v) → r''
59. Rotate(A, If[8.5 < o ≤ 9.5, ((-(o - 8.5)) * π), (-π)], J) → A'_5
60. Rotate(C, If[8.5 < o ≤ 9.5, ((-(o - 8.5)) * π), (-π)], J) → C'_2
61. Rotate(F, If[8.5 < o ≤ 9.5, ((-(o - 8.5)) * π), (-π)], J) → F'_1
62. Rotate(D, If[8.5 < o ≤ 9.5, ((-(o - 8.5)) * π), (-π)], J) → D'_1
63. Polygon(A'_5, C'_2, F'_1, D'_1) → poly1', a'_5, c'_2, f'_1, d'_1
64. Dilate(I, If[10 < o ≤ 11, 11 - o, 0], D) → I'_2
65. Vector(I, I'_2) → w
66. Translate(I, w) → I'_3
67. Translate(I'_1, w) → M
68. Segment(I'_3, M) → q_1
69. Dilate(I, If[11 < o ≤ 12, 12 - o, 0], M) → I'_4
70. Dilate(I, If[11 < o ≤ 12, 12 - o, 0], M) → I'_5
71. Vector(I, I'_5) → u_1
72. Translate(I, u_1) → I'_6
73. Translate(I'_1, u_1) → N
74. Segment(I'_6, N) → r_1