利用平行四边形推导梯形面积公式

GeoGebra 命令及参数

1. Point(Circle[A, l_{ab}]) → B
2. Line(A, B) → a_1
3. Point(a_1) → E
4. Segment(E, F) → e
5. Vector(V1, V2) → u
6. Polygon(A, B, C, D) → poly1, a, b, c, d
7. Angle(a, e) → α
8. Circle(W_o, sqrt(8)) → g
9. Point(g) → W_{2o}
10. Point(g) → W_{1o}
11. Point(g) → W_n
12. Circle(W_o, sqrt(3)) → f
13. Point(f) → K
14. Line(C, D) → c_1
15. Line(E, F) → b_1
16. Line(W_o, W_n) → w_i
17. Angle(K, W_o, W_n) → β
18. Rotate(W_{1o}, (-β), W_o) → W_1
19. Rotate(W_{2o}, (-β), W_o) → W_2
20. Midpoint(E, F) → M_{EF}
21. Rotate(A, (-β), M_{EF}) → A'_1
22. Rotate(B, (-β), M_{EF}) → B'_1
23. Rotate(C, (-β), M_{EF}) → C'_1
24. Rotate(D, (-β), M_{EF}) → D'
25. Polygon(A'_1, B'_1, C'_1, D') → poly1', a1, b1, c1, d1
26. Translate(A'_1, u) → G
27. Translate(B'_1, u) → H
28. Translate(C'_1, u) → I
29. Translate(D', u) → D''
30. Polygon(G, H, I, D'') → poly1'', a2, b2, c2, d2
31. Circle(B, ε) → k
32. IsInRegion(I, k) → snapBI