切线与弦的夹角等于弦所对的圆周角

GeoGebra 命令及参数

1. Intersect(xAxis, yAxis) → A_1
2. Point(yAxis) → B_1
3. Circle(A_1, B_1) → c
4. Tangent(T, c) → a, b
5. Intersect(c, b, 1) → C
6. Point(c) → B
7. Point(c) → A
8. Polygon(C, B, A) → poly1, g, d, e
9. LineBisector(e) → f
10. Line(B, f) → h
11. Angle(A, B, C) → α
12. Angle(T, C, B) → ta2
13. Angle(C, A, B) → γ
14. Vector(A, C) → u
15. Vector(A, B) → v
16. Vector(C, B) → w
17. Vector(C, T) → z
18. Vector(A_1, B) → i
19. Vector(A_1, A) → j
20. Vector(A_1, C) → k
21. Angle(T, C, A) → ta