梯形面积计算 by Toby Jacobson (3)

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. Polygon(F, E, D, G) → poly1, f_1, e, d, g_1
8. OrthogonalLine(C, e) → h
9. Intersect(f, h) → H
10. Segment(C, H) → height
11. Midpoint(D, G) → I
12. Rotate(F, (-α), I) → F'
13. Rotate(E, (-α), I) → E'
14. Rotate(D, (-α), I) → D'
15. Rotate(G, (-α), I) → G'
16. Polygon(F', E', D', G') → poly1', f', base1, d', g'
17. Intersect(base1, d') → J
18. Intersect(f', base1) → K
19. Segment(J, K) → i
20. Segment(F, G) → base2