等差数列的前n项和

GeoGebra 命令及参数

1. Sequence(Sequence[(j, (-i)), j, 1, i], i, 1, 10) → l1
2. Sequence(Sequence[(j, (-i)), j, 1, 3], i, 3, 20, 2) → l2
3. Sequence(Sequence[(j, (-i)), j, 4, i], i, 3, 20, 2) → l3
4. Sequence((0, k), k, -3, -11, -1) → l5
5. Sequence((0, k), k, -3, -19, -2) → l4
6. Sequence(Vector[Element[l4, k], Element[l5, k]], k, 1, 9) → l6
7. Sequence(Translate[Element[l2, k], Vector[Element[l6, k]]], k, 1, 9) → l7
8. Sequence(Translate[Element[l3, k], Vector[Element[l6, k]]], k, 1, 9) → l8
9. Vector(A, B) → u
10. If(0 ≤ a < 1, Vector[Dilate[u, a, A]], Vector[If[a ≥ 1, u]]) → v
11. Translate(l7, v) → l9
12. Translate(l8, v) → l10
13. If(1 ≤ a < 2, Rotate[l9, β, C], If[a ≥ 2, Rotate[l9, α, C]]) → l11
14. If(1 ≤ a < 2, Rotate[l10, β, C], If[a ≥ 2, Rotate[l10, α, C]]) → l12
15. Vector(D, E) → w
16. If(2 ≤ a < 3, Vector[Dilate[w, a - 2, D]], Vector[If[a ≥ 3, w]]) → b
17. Translate(l11, b) → l13
18. Translate(l12, b) → l14
19. Segment(F, G) → f
20. Segment(H, I) → g
21. Segment(J, K) → h
22. Segment(L, M) → i
23. Segment(N, O) → j
24. Sequence((-1, k), k, -3, -11, -1) → l17
25. Sequence(Text[Element[l15, k], Element[l17, k]], k, 1, 9) → l16
26. Segment(P, Q) → k
27. Segment(R, S) → l
28. Sequence((24, k), k, -3, -11, -1) → l18
29. Sequence(Text[Element[l15, k], Element[l18, 10 - k]], k, 1, 9) → l19
30. PolyLine(T, U, F_1, G_1, H_1, I_1, J_1, K_1, L_1, M_1, V, W, Z, A_1, B_1, C_1, D_1, E_1) → m
31. Polygon(N_1, O_1, Q_1, P_1) → q1, n_1, o_1, q_1, p_1
32. Segment(R_1, S_1) → n