余弦定理证明 by yerkin

GeoGebra 命令及参数

1. Ray(C, B) → a
2. Ray(C, A) → b
3. Circle(B, C) → c
4. Intersect(c, b, 2) → D
5. Intersect(c, a, 2) → E
6. Segment(E, D) → d
7. Line(A, B) → e
8. Intersect(c, e, 1) → F
9. Intersect(c, e, 2) → G
10. Angle(E, D, C) → α
11. Segment(D, A) → f
12. Segment(A, C) → g
13. Segment(E, B) → h
14. Segment(B, C) → i
15. Segment(G, B) → j
16. Segment(B, A) → k
17. Segment(A, F) → l
18. Polygon(A, B, C) → poly1, c_1, a_1, b_1
19. Polygon(D, G, A) → poly2, a_2, d_1, g_1
20. Polygon(A, F, C) → poly3, c_2, a_3, f_1
21. Angle(A, C, B) → β