梯形面积公式

GeoGebra 命令及参数

1. Polygon(A, B, C) → t1, c, a, b
2. Line(C, c) → f
3. Point(f) → D
4. Polygon(C, D, A) → t2, a_1, c_1, d
5. Polygon(D, A, C) → t3, c_2, d_1, a_2
6. OrthogonalLine(B, c) → g
7. OrthogonalLine(C, a_1) → h
8. OrthogonalLine(D, f) → i
9. OrthogonalLine(A, f) → j
10. Intersect(f, g) → E
11. Segment(E, C) → k
12. Intersect(f, j) → F
13. Segment(F, D) → l
14. Midpoint(D, F) → G
15. Midpoint(C, E) → H
16. OrthogonalLine(G, l) → m
17. OrthogonalLine(H, f) → n
18. Intersect(m, c) → I
19. Intersect(n, c) → J
20. Polygon(H, G, I, J) → q1, h_1, g_1, i_1, j_1
21. Polygon(D, F, A) → t4, a_3, d_2, f_1
22. Polygon(E, C, B) → t5, b_1, e, c_3
23. Segment(B, A) → p
24. Intersect(h, i_1) → K
25. Polygon(C, K, B) → t6, b_2, c_4, k_1
26. Intersect(i, i_1) → L
27. Polygon(D, L, A) → t7, a_4, d_3, l_1