三角形能否密铺?——中点旋转法探索
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① 本范例通过动画演示任意三角形能否利用中点旋转规则(17种壁纸群之一)实现平面密铺,直观展示三角形拼接覆盖平面的过程。② 核心数学概念包括平面密铺(tessellation)、旋转对称、中点旋转、壁纸群以及三角形内角和为180°的性质。③ 作图要点:使用GeoGebra的Polygon命令构造三角形poly1,通过Midpoint命令取各边中点,再利用Rotate命令以中点为中心按指定角度旋转三角形,生成多个旋转副本(如A'、B'、C'等),并重复操作形成密铺图案;涉及对象包括点A、B、C,边a、b、c,以及多级旋转后的三角形。④ 适合中学几何或数学拓展课程,帮助学生理解密铺条件与变换几何,也可用于探索性学习或教师课堂演示。
GeoGebra 命令及参数
Polygon(A, B, C) → poly1, c, a, bMidpoint(B, C) → DMidpoint(C, A) → EMidpoint(A, B) → FRotate(A, rot, F) → A'Rotate(B, rot, F) → B'Rotate(C, rot, F) → C'Polygon(A', B', C') → poly1', c', a', b'Rotate(A, rot, D) → A'_1Rotate(B, rot, D) → B'_1Rotate(C, rot, D) → C'_1Polygon(A'_1, B'_1, C'_1) → poly1'_1, c'_1, a'_1, b'_1Rotate(A, rot, E) → A'_2Rotate(B, rot, E) → B'_2Rotate(C, rot, E) → C'_2Polygon(A'_2, B'_2, C'_2) → poly1'_2, c'_2, a'_2, b'_2Rotate(A, 180*°, F) → A'_3Rotate(B, 180*°, F) → B'_3Rotate(C, 180*°, F) → C'_3Polygon(A'_3, B'_3, C'_3) → poly1'_3, c'_3, a'_3, b'_3Rotate(A, 180*°, D) → A'_4Rotate(B, 180*°, D) → B'_4Rotate(C, 180*°, D) → C'_4Polygon(A'_4, B'_4, C'_4) → poly1'_4, c'_4, a'_4, b'_4Rotate(A, 180*°, E) → A'_5Rotate(B, 180*°, E) → B'_5Rotate(C, 180*°, E) → C'_5Polygon(A'_5, B'_5, C'_5) → poly1'_5, c'_5, a'_5, b'_5Midpoint(C'_3, B) → GMidpoint(B, A'_4) → HMidpoint(A'_4, C) → IMidpoint(C, B'_5) → JMidpoint(B'_5, A) → KMidpoint(C'_3, A) → LRotate(A'_3, rot, G) → MRotate(B'_3, rot, G) → NRotate(C'_3, rot, G) → OPolygon(M, N, O) → poly2, o, m, nRotate(A'_3, rot, L) → PRotate(B'_3, rot, L) → QRotate(C'_3, rot, L) → RPolygon(P, Q, R) → poly3, r, p, qRotate(A'_4, rot, H) → SRotate(B'_4, rot, H) → TRotate(C'_4, rot, H) → UPolygon(S, T, U) → poly4, u, s, tRotate(A'_4, rot, I) → VRotate(B'_4, rot, I) → WRotate(C'_4, rot, I) → ZPolygon(V, W, Z) → poly5, z, v, wRotate(A'_5, rot, K) → A_1Rotate(B'_5, rot, K) → B_1Rotate(C'_5, rot, K) → C_1Polygon(A_1, B_1, C_1) → poly6, c_1, a_1, b_1Rotate(A'_5, rot, J) → D_1Rotate(B'_5, rot, J) → E_1Rotate(C'_5, rot, J) → F_1Polygon(D_1, E_1, F_1) → poly7, f_1, d_1, e_1Angle(C, A, B) → αAngle(A, B, C) → βAngle(B, C, A) → γMidpoint(a'_3) → G_1Midpoint(b'_3) → H_1Midpoint(b'_4) → I_1Midpoint(c'_4) → J_1Midpoint(c'_5) → K_1Midpoint(a'_5) → L_1Rotate(A'_3, 180*°, H_1) → M_1Rotate(B'_3, 180*°, H_1) → N_1Rotate(C'_3, 180*°, H_1) → O_1Polygon(M_1, N_1, O_1) → poly8, o_1, m_1, n_1Rotate(A'_4, 180*°, I_1) → P_1Rotate(B'_4, 180*°, I_1) → Q_1Rotate(C'_4, 180*°, I_1) → R_1Polygon(P_1, Q_1, R_1) → poly9, r_1, p_1, q_1Rotate(A'_4, 180*°, J_1) → S_1Rotate(B'_4, 180*°, J_1) → T_1Rotate(C'_4, 180*°, J_1) → U_1Polygon(S_1, T_1, U_1) → poly10, u_1, s_1, t_1Rotate(A'_5, 180*°, K_1) → V_1Rotate(B'_5, 180*°, K_1) → W_1Rotate(C'_5, 180*°, K_1) → Z_1Polygon(V_1, W_1, Z_1) → poly11, z_1, v_1, w_1Rotate(A'_5, 180*°, L_1) → A_2Rotate(B'_5, 180*°, L_1) → B_2Rotate(C'_5, 180*°, L_1) → C_2Polygon(A_2, B_2, C_2) → poly12, c_2, a_2, b_2Rotate(A'_3, 180*°, G_1) → D_2Rotate(B'_3, 180*°, G_1) → E_2Rotate(C'_3, 180*°, G_1) → F_2Polygon(D_2, E_2, F_2) → poly13, f_2, d_2, e_2Midpoint(t_1) → G_2Midpoint(r_1) → H_2Rotate(P_1, 180*°, H_2) → I_2Rotate(Q_1, 180*°, H_2) → J_2Rotate(R_1, 180*°, H_2) → K_2Polygon(I_2, J_2, K_2) → poly9', k_2, i_2, j_2Rotate(S_1, 180*°, G_2) → L_2Rotate(T_1, 180*°, G_2) → M_2Rotate(U_1, 180*°, G_2) → N_2Polygon(L_2, M_2, N_2) → poly10', n_2, l_2, m_2Midpoint(a) → O_2Midpoint(m_1) → P_2Midpoint(c) → Q_2Angle(I_1, B, H_2) → δAngle(H_1, B, Q_2) → εAngle(H_2, B, P_2) → ζAngle(P_2, B, H_1) → ηAngle(O_2, B, I_1) → θ
AI 绘图提示语参考
画一个三角形,然后找到每条边的中点,并将三角形围绕这些中点进行旋转,展示旋转后的三角形如何紧密排列覆盖整个平面,形成无缝的镶嵌图案。通过多次旋转和重复排列,展示三角形的旋转对称性和镶嵌条件,强调数学中的旋转对称、镶嵌和 wallpaper groups 的概念。
以上提示语为根据原始绘图命令整理而来,仅供参考。