四边形重心作图：利用中点与交点确定质心

GeoGebra 命令及参数

1. Polygon(A, B, C, D) → poly1, a, b, c, d
2. Polygon(A, C, B) → poly2, b_1, a_1, c_1
3. Polygon(A, D, C) → poly3, c_2, a_2, d_1
4. Midpoint(a) → E
5. Midpoint(b) → F
6. Segment(A, F) → e
7. Segment(C, E) → f
8. Intersect(e, f) → G_1
9. Midpoint(d) → G
10. Midpoint(c) → H
11. Segment(A, H) → g
12. Segment(C, G) → h
13. Intersect(g, h) → G_2
14. Segment(G_1, G_2) → i
15. Polygon(E, G, H, F) → poly4, e_1, g_1, h_1, f_1
16. Segment(E, H) → j
17. Segment(G, F) → k
18. Intersect(j, k) → I
19. Segment(B, D) → l
20. Segment(B, G) → m
21. Segment(D, E) → n
22. Segment(D, F) → p
23. Segment(B, H) → q
24. Intersect(n, m) → K
25. Intersect(p, q) → L
26. Segment(K, L) → r
27. Intersect(i, r) → J
28. Segment(A, C) → s