梯形面积 by Steve Phelps

GeoGebra 命令及参数

1. Segment(B, C) → f
2. Line(A, f) → g
3. Point(g) → D
4. Polygon(A, B, C, D) → q1, a, b, c, d
5. Point(d) → E
6. OrthogonalLine(E, b) → h
7. Intersect(h, b) → F
8. Segment(E, F) → i
9. Midpoint(c) → G
10. Rotate(A, (-((180° * e))), G) → A'
11. Rotate(B, (-((180° * e))), G) → B'
12. Rotate(C, (-((180° * e))), G) → C'
13. Rotate(D, (-((180° * e))), G) → D'
14. Polygon(A', B', C', D') → q1', a', b', c', d'
15. Rotate(E, (-((180° * e))), G) → E'
16. Rotate(F, (-((180° * e))), G) → F'
17. Segment(E', F') → i'