梯形面积计算 by Jeff Caldwell

GeoGebra 命令及参数

1. Segment(A, B) → a_2
2. Line(C, a_2) → b_2
3. Point(b_2) → D
4. Polygon(A, C, D, B) → P, a_1, a, d, b
5. Midpoint(D, B) → E
6. Rotate(A, (-rotate), E) → A'
7. Rotate(C, (-rotate), E) → C'
8. Rotate(D, (-rotate), E) → D'
9. Rotate(B, (-rotate), E) → B'
10. Polygon(A', C', D', B') → P', a', c', d', b'
11. Line(A, B) → e
12. OrthogonalLine(D, e) → f
13. Intersect(f, e) → F
14. Segment(A, F) → c
15. Midpoint(B', A') → G
16. Midpoint(D', C') → H
17. If(rotate ≥ 0°, H) → I
18. If(rotate > 0°, H) → J
19. If(rotate > 0°, G) → K
20. Segment(D, F) → h_1
21. Angle(D, F, A) → β
22. Midpoint(a_2) → L
23. Midpoint(h_1) → M
24. Segment(A, D) → g
25. Polygon(A, C, D) → h_2, d_1, a_3, c_1
26. Polygon(A, D, B) → poly2, b_1, a_4, d_2
27. Line(D, C) → i
28. OrthogonalLine(A, i) → j
29. Intersect(i, j) → N
30. Segment(N, C) → k
31. Segment(A, N) → h
32. Intersect(h, k) → O
33. Angle(A, O, D) → α