平面几何入门：旋转与对称

GeoGebra 命令及参数

1. Plane(A, B, C) → p
2. Mirror(O, p) → O'
3. Line(O, O') → f
4. Intersect(p, f) → D
5. OrthogonalLine(D, Vector[D, O], Vector[D, B]) → j
6. Plane(f, j) → q
7. Dilate(O, If[0 < SlideMe ≤ 1, 1 - SlideMe, 0], D) → O'_{1}
8. Segment(O, O'_{1}) → g
9. Dilate(D, If[1 < SlideMe ≤ 2, 2 - SlideMe, 0], O') → D'
10. Segment(D, D') → h
11. OrthogonalLine(D, Vector[O, O'], xOyPlane) → i
12. Point(i) → E
13. Rotate(O, If[2 < SlideMe ≤ 3, ((SlideMe - 2) * π), π], D, q) → O'_{2}
14. Rotate(O'_{1}, If[2 < SlideMe ≤ 3, ((SlideMe - 2) * π), π], D, q) → F
15. Segment(O'_{2}, F) → g'
16. Point(j) → G
17. Angle(G, D, O) → α