余弦加法定理的几何证明

GeoGebra 命令及参数

1. Point(yAxis) → B_1
2. Intersect(xAxis, yAxis) → A
3. Circle(A, B_1) → c
4. Point(c) → C_1
5. Rotate(C_1, β°, A) → C'_1
6. Line(A, C'_1) → f
7. Intersect(c, f, 2) → C
8. Line(A, C_1) → g
9. OrthogonalLine(C, g) → p
10. Intersect(g, p) → B
11. Rotate(C_1, α°, A) → D
12. Polygon(A, B, C) → poly1, q, r, s
13. Line(A, D) → h
14. Polygon(A, C, D) → poly2, t, a, b
15. Angle(poly2) → γ, δ, ε
16. Angle(poly1) → ζ, η, θ
17. OrthogonalLine(D, g) → k
18. Distance(C, D) → distanceCD
19. Angle(B, A, D) → ι
20. Intersect(k, q) → E
21. Distance(A, E) → distanceAE