9点锥曲线（9-Punkte-Kegelschnitt）构造

GeoGebra 命令及参数

1. Polygon(A, B, C) → d1, c, a, b
2. Line(A, P) → f
3. Line(B, P) → g
4. Line(P, C) → h
5. Midpoint(P, A) → D
6. Midpoint(P, B) → E
7. Midpoint(P, C) → F
8. Midpoint(b) → G
9. Midpoint(a) → H_{1}
10. Midpoint(c) → I
11. Intersect(f, a) → J
12. Intersect(g, b) → K
13. Intersect(h, c) → L
14. Conic(D, L, I, E, F) → d
15. Line(A, B) → i
16. Line(B, C) → j
17. Line(A, C) → k
18. OrthogonalLine(A, j) → l
19. OrthogonalLine(B, k) → m
20. OrthogonalLine(C, i) → n
21. Intersect(n, i) → M
22. Intersect(l, j) → N
23. Intersect(m, k) → O
24. Segment(C, M) → p
25. Segment(A, N) → q
26. Segment(B, O) → r
27. Intersect(l, m) → H
28. Segment(C, I) → s
29. Segment(A, H_{1}) → t
30. Segment(B, G) → e
31. Intersect(s, t) → S
32. Circle(A, B, C) → c_1
33. Center(c_1) → U