到两焦点距离之和为常数：椭圆的轨迹演示

GeoGebra 命令及参数

1. Intersect(xAxis, yAxis) → E
2. Ray((0.01, 0), (1, 0)) → xx
3. Ray((0.01, 0), (0, 1)) → yy
4. Point(axis) → F_1
5. Mirror(F_1, E) → F_2
6. Line(B, xAxis) → i
7. Point(i) → D
8. Point(i) → C
9. Segment(C, D) → aa
10. Circle(F_2, a) → e
11. Circle(F_1, a) → d
12. Intersect(e, d) → P, G, ,
13. Ellipse(F_2, F_1, P) → f
14. Point(f) → R
15. Distance(E, F_1) → c
16. Segment(F_2, R) → b
17. Segment(R, F_1) → g
18. If(aa > (2 * c), true, false) → sh
19. Polygon(Corner[1], Corner[2], (x(Corner[2]), y(Corner[2]) + (0.28 * Distance[Corner[3], Corner[2]])), (x(Corner[4]), y(Corner[1]) + (0.28 * Distance[Corner[3], Corner[2]]))) → Bottom, j, k, l, m
20. Line(F_1, F_2) → n
21. OrthogonalLine(E, n) → p
22. Intersect(f, n) → A, K
23. Intersect(f, p) → L, M
24. Point(K, Vector[((UnitVector[p] * 1.2) * a)]) → K1
25. Mirror(K1, p) → K1'
26. Vector(K1, K) → u
27. Vector(K1', A) → v
28. Segment(K1, K1') → q
29. Midpoint(q) → N
30. Point(M, Vector[(-(((UnitVector[n] * 1.28) * a)))]) → M1
31. Mirror(M1, n) → M1'
32. Segment(M1, M1') → r
33. Vector(M1', L) → w
34. Vector(M1, M) → s
35. Midpoint(r) → Q
36. If(y(M) > 0, M, L) → PO
37. If(y(M) < 0, M, L) → NE