梯形面积计算 by Toby Jacobson (2)

GeoGebra 命令及参数

1. Line(A, B) → f
2. Line(C, f) → g
3. Point(g) → D
4. Point(g) → E
5. Point(f) → F
6. Point(f) → G
7. Segment(F, D) → h
8. Segment(G, E) → i
9. OrthogonalLine(C, g) → j
10. Intersect(f, j) → H
11. Segment(C, H) → height
12. Midpoint(h) → I
13. Midpoint(i) → J
14. Polygon(F, I, J, G) → poly1, f_1, i_1, j_1, g_1
15. Polygon(I, D, E, J) → poly2, i_2, d, e, j_2
16. Rotate(I, (-α), J) → I'
17. Rotate(D, (-α), J) → D'
18. Rotate(E, (-α), J) → E'
19. Rotate(J, (-α), J) → J'
20. Polygon(I', D', E', J') → poly2', i', d', e', j'
21. Segment(D, E) → l
22. Segment(E', D') → base1
23. Segment(F, G) → base2