Relation between angles formed at centre and perimeter of circle

GeoGebra Commands & Parameters

1. Circle(A, 2.5) → c
2. Point(c) → B
3. Point(c) → C
4. Segment(B, C) → f
5. Point(c) → D
6. Segment(B, D) → g
7. Segment(D, C) → h
8. Rotate(B, 90°, D) → B'
9. Angle(B, D, B') → α
10. Circle(E, 2.5) → d
11. Point(d) → F
12. Point(d) → G
13. Segment(F, G) → i
14. Point(d) → H
15. Segment(F, H) → j
16. Segment(H, G) → k
17. Angle(F, H, G) → β
18. Point(d) → I
19. Segment(F, I) → l
20. Segment(I, G) → m
21. Angle(G, I, F) → γ
22. Circle(J, 2.5) → e
23. Point(e) → K
24. Segment(K, J) → n
25. Point(e) → L
26. Segment(J, L) → p
27. Point(e) → M
28. Segment(M, L) → q
29. Segment(M, K) → r
30. Angle(K, M, L) → δ
31. Angle(K, J, L) → ε
32. Circle(N, 2.5) → s
33. Point(s) → O
34. Segment(O, N) → t
35. Point(s) → P
36. Segment(P, N) → a
37. Rotate(O, 70°, N) → O'
38. Angle(O, N, O') → ζ
39. Segment(N, O') → b
40. Point(s) → R
41. Segment(O, R) → g_1
42. Segment(O', R) → h_1
43. Angle(O, R, O') → η
44. Circle(S, 2.5) → c_1
45. Point(c_1) → T
46. Segment(T, S) → i_1
47. Rotate(T, 100°, S) → T'
48. Angle(T, S, T') → θ
49. Segment(T', S) → j_1
50. Point(c_1) → U
51. Segment(T, U) → k_1
52. Segment(U, T') → l_1
53. Angle(T', U, T) → ι