梯形面积动态演示与几何构造

GeoGebra 命令及参数

1. Segment(A, B) → al
2. Line(D, al) → bl
3. Segment(D, A) → c
4. Point(bl) → C
5. Segment(C, B) → e
6. Midpoint(C, B) → E
7. Segment(D, E) → f
8. Segment(D, C) → d
9. Rotate(D, -1.0 * α, E) → G
10. Rotate(C, -1.0 * α, E) → D'
11. Segment(G, E) → g
12. Segment(D', E) → he
13. Segment(G, D') → i
14. Polygon(D, A, B, E) → poly1, c_1, a_1, b_1, e_1
15. Polygon(D, C, E) → poly2, e_2, c_2, d_1
16. Polygon(E, D', G) → poly3, c', e_3, d'
17. OrthogonalLine(D, al) → j
18. Intersect(j, al) → F
19. Segment(D, F) → k
20. Point(al) → H
21. Midpoint(D, F) → I
22. Midpoint(D, C) → J
23. Midpoint(B, G) → K
24. Midpoint(i) → L