π的几何意义与圆周率概念

GeoGebra 命令及参数

1. Segment(((-r), 0), (r, 0)) → f
2. Rotate(((-r), 0), If[0 < a ≤ 1, ((-a) * pi / 2), ((-pi)) / 2], (r, 0)) → A
3. Segment((r, 0), A) → g
4. Rotate(B, 2, (0, 0)) → B'
5. Rotate(B', 2, (0, 0)) → B''
6. Rotate(B'', 2, (0, 0)) → B'''
7. Rotate(B, If[1.5 < a ≤ 2.5, ((a - 1.5) * 2), 2], (0, 0)) → B'_{1}
8. CircleArc((0, 0), B, B'_{1}) → c
9. Circle(B'_{1}, (2 * r) - c) → d
10. Line((0, 0), B'_{1}) → h
11. OrthogonalLine(B'_{1}, h) → i
12. Intersect(d, i, 2) → C
13. Segment(B'_{1}, C) → j
14. Dilate(B, If[3 ≤ a ≤ 4, 4 - a, 0], B') → D
15. Vector(B, D) → u
16. Translate(f, u) → f'
17. Line((0, 0), B') → k
18. OrthogonalLine(B', k) → l
19. Point(l) → E
20. Point(p) → F
21. Angle(F, B', E) → α
22. Rotate(f', If[3 < a ≤ 4, ((a - 3) * α), α], D) → f''
23. Rotate(B', If[4.5 < a ≤ 5.5, ((a - 4.5) * 2), 2], (0, 0)) → B''_{1}
24. CircleArc((0, 0), B', B''_{1}) → e
25. Line((0, 0), B''_{1}) → m
26. OrthogonalLine(B''_{1}, m) → n
27. Circle(B''_{1}, (2 * r) - e) → q
28. Intersect(q, n, 2) → G
29. Segment(B''_{1}, G) → s
30. Rotate(f, If[6 < a ≤ 7, ((a - 6) * pi / 2), pi / 2], B) → f'_{1}
31. Rotate(B, If[7.5 < a ≤ 8.5, ((-(a - 7.5)) * 2), -2], (0, 0)) → B'_{2}
32. CircleArc((0, 0), B'_{2}, B) → t
33. Circle(B'_{2}, (2 * r) - t) → c_1
34. Line((0, 0), B'_{2}) → b
35. OrthogonalLine(B'_{2}, b) → f_1
36. Intersect(c_1, f_1, 1) → H
37. Segment(B'_{2}, H) → g_1
38. Circle((0, 0), r) → d_1
39. Vector(I, J) → v
40. Rotate((r, 0), 1, (0, 0)) → K
41. Rotate((r, 0), 3, (0, 0)) → L
42. Mirror(K, y = 0) → K'
43. RotateText(text2, pi / 4) → text7