平行四边形的面积 by David T

GeoGebra 命令及参数

1. Segment(A, B) → a_2
2. Line(C, a_2) → b_2
3. Point(b_2) → D
4. Polygon(A, D, B) → P, a, b, d
5. Midpoint(D, B) → E
6. Rotate(A, (-rotateΔ), E) → A'
7. Rotate(C, (-rotateΔ), E) → C'
8. Rotate(D, (-rotateΔ), E) → D'
9. Rotate(B, (-rotateΔ), E) → B'
10. Polygon(A', D', B') → P', g, i, j
11. Line(A, B) → e
12. OrthogonalLine(D, e) → f
13. Intersect(f, e) → F
14. Midpoint(B', A') → G
15. Midpoint(D', C') → H
16. If(rotateΔ ≥ 0°, H) → I
17. If(rotateΔ > 0°, H) → J
18. If(rotateΔ > 0°, G) → K
19. Segment(D, F) → h
20. Angle(D, F, A) → β
21. Midpoint(h) → L
22. Midpoint(a_2) → M