抛物线的另一个反射性质

GeoGebra 命令及参数

1. Line(A, B) → a
2. Slope(a) → b
3. PointIn(d) → C
4. Parabola(C, a) → e
5. OrthogonalLine(C, a) → f
6. Point(e) → D
7. Tangent(D, e) → g,
8. OrthogonalLine(C, f) → h
9. Intersect(e, h, 1) → E
10. Intersect(e, h, 2) → F
11. Line(D, f) → i
12. Circle(D, 1) → k
13. Intersect(k, i, 2) → G
14. Ray(D, G) → j
15. OrthogonalLine(D, f) → l
16. Intersect(f, l) → H
17. Distance(C, D) → m
18. Circle(D, (2 * m)) → p
19. Intersect(p, j, 1) → I
20. Dilate(C, If[0 < n ≤ 1, 1 - n, 0], D) → C'
21. Vector(C, C') → u
22. Dilate(D, If[1 < n ≤ 2, 2 - n, 0], I) → D'
23. Vector(D, D') → v
24. Distance(C, D) → o
25. Circle(D, (0.3 * o)) → q
26. Intersect(q, g, 2) → K
27. Segment(C, D) → r
28. Intersect(q, r, 1) → J
29. CircleSector(D, J, K) → s
30. Angle(J, D, K) → α
31. Rotate(s, If[2 < s ≤ 3, ((-(n - 2)) * (180° - α)), ((-(n - 2)) * (180° - α))], D) → s'
32. CircleArc(D, J, K) → t
33. Circle(D, J) → c_1
34. Intersect(c_1, g, 1) → L
35. CircleSector(D, L, J) → d_1
36. Rotate(d_1, If[2 < s ≤ 3, ((n - 2) * α), ((n - 2) * α)], D) → e_1
37. CircleArc(D, L, J) → f_1
38. Circle(D, C) → g_1
39. Intersect(g_1, g, 1) → M
40. Intersect(g_1, g) → N, O
41. Vector(D, N) → w
42. Vector(D, O) → u_1
43. Intersect(a, f) → P
44. Angle(B, P, C) → β