平行四边形面积计算 by Chip Rollinson

GeoGebra 命令及参数

1. Point(a) → B
2. Point(a) → C
3. Segment(B, C) → b
4. Vector(B, C) → u
5. Point(c) → D
6. Segment(B, D) → d
7. Segment(D, E) → e
8. Segment(E, C) → f
9. Segment(C, B) → g
10. Polygon(B, D, E, C) → poly1, b_1, d_1, e_1, c_1
11. Line(B, C) → h_1
12. OrthogonalLine(E, h_1) → i
13. OrthogonalLine(D, h_1) → j
14. Intersect(h_1, i) → F
15. Intersect(h_1, j) → G
16. Angle(D, G, B) → α
17. Angle(E, F, B) → β
18. Segment(E, F) → h
19. Segment(D, G) → l