抛物线段:阿基米德洞察
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①本范例动态演示抛物线段的形成及其与切线、角度的关系;②涉及核心数学概念包括抛物线、切线、角度、直线、向量等;③作图要点:运用了Line, Segment, Slope, Intersect, Polygon, OrthogonalLine, Circle, Dilate, Vector, Translate, Point, Angle, Rotate, Midpoint等GeoGebra命令与对象;④适合高中及以上学生及数学爱好者用于理解抛物线性质及几何作图。
GeoGebra 命令及参数
Line(A, B) → gSegment(A, B) → jSlope(g) → dIntersect(f', h, 1) → CPolygon(A, D, B) → t1, b_1, a_1, d_1OrthogonalLine(D, g) → lIntersect(g, l) → ESlope(b_1) → mSlope(a_1) → m_1Intersect(f', n) → FIntersect(f', p) → HPolygon(A, I, D) → t2, d_2, a_2, i_1Polygon(D, G, B) → t3, b_2, d_3, g_1Segment(A, D) → qSegment(D, B) → rSegment(B, G) → sSegment(G, D) → tSegment(A, I) → eSegment(I, D) → f_1Line(A, B) → h_1Circle(A, t) → c_1Intersect(c_1, j_1, 2) → JCircle(A, r) → e_1Circle(J, s) → p_1Intersect(e_1, p_1, 2) → KDilate(I, If[0 < o ≤ 1, 1 - o, 0], J) → I'Polygon(A, I', D) → t4, d_4, a_3, i'Segment(A, I') → l_1Segment(I', D) → n_1Line(D, l_1) → q_1Dilate(D, If[3 < o ≤ 4, 4 - o, 0], K) → D'Polygon(A, I', D') → t5, d', a_4, i'_1Segment(I', D') → r_1Segment(D', A) → s_1Dilate(I', If[5 < o ≤ 6, 6 - o, 0], G) → I''Vector(I', I'') → uTranslate(A, u) → A'Translate(I', u) → I''_1Translate(D', u) → D''Polygon(A', I''_1, D'') → t5', d'', a', i''_1Line(I', t) → t_1Point(t_1) → LAngle(L, I', A) → αRotate(A', If[5 < o ≤ 6, ((-(o - 5)) * α), (-α)], I''_1) → A''Rotate(I''_1, If[5 < o ≤ 6, ((-(o - 5)) * α), (-α)], I''_1) → MRotate(D'', If[5 < o ≤ 6, ((-(o - 5)) * α), (-α)], I''_1) → D'''Polygon(A'', M, D''') → t5'', d''', a'', m_2Midpoint(A, B) → NMidpoint(N, B) → OMidpoint(A, N) → PMidpoint(A, P) → QMidpoint(P, N) → RMidpoint(N, O) → SMidpoint(O, B) → TDilate(A, If[7 < o ≤ 8, 8 - o, 0], Q) → A'_1Segment(A, A'_1) → f_2Rotate(A, If[8 < o ≤ 9, ((o - 8) * π), π], Q) → A'_2Rotate(A'_1, If[8 < o ≤ 9, ((o - 8) * π), π], Q) → USegment(A'_2, U) → g_2Rotate(A'_2, If[9 < o ≤ 10, ((o - 9) * π), π], A'_2) → VRotate(U, If[9 < o ≤ 10, ((o - 9) * π), π], A'_2) → U'Segment(V, U') → h_2Rotate(V, If[10 < o ≤ 11, ((o - 10) * π), π], U') → V'Rotate(U', If[10 < o ≤ 11, ((o - 10) * π), π], U') → U''Segment(V', U'') → i_2Rotate(V', If[11 < o ≤ 12, ((o - 11) * π), π], V') → V''Rotate(U'', If[11 < o ≤ 12, ((o - 11) * π), π], V') → U'''Segment(V'', U''') → j_2Rotate(V'', If[12 < o ≤ 13, ((o - 12) * π), π], U''') → V'''Rotate(U''', If[12 < o ≤ 13, ((o - 12) * π), π], U''') → WSegment(V''', W) → k_2Rotate(V''', If[13 < o ≤ 14, ((o - 13) * π), π], V''') → ZRotate(W, If[13 < o ≤ 14, ((o - 13) * π), π], V''') → W'Segment(Z, W') → l_2Rotate(Z, If[14 < o ≤ 15, ((o - 14) * π), π], W') → Z'Rotate(W', If[14 < o ≤ 15, ((o - 14) * π), π], W') → W''Segment(Z', W'') → n_2Circle(D, n_2) → c_2Intersect(c_2, k_1) → A_1, B_1Dilate(M, If[16 < o ≤ 17, 17 - o, 0], B_1) → M'Polygon(D, M', B) → t6, b_3, d_5, m'Segment(D, M') → p_2Segment(M', B) → q_2Midpoint(M', W') → C_1Line(A, B) → r_2Circle(A, (7 / 8 * Distance[A, B])) → e_2Intersect(e_2, r_2) → D_1, E_1Polygon(A, E_1, D) → t7, d_6, a_5, e_3Polygon(E_1, B, D) → t8, d_7, e_4, b_4Midpoint(M', E_1) → F_1Dilate(D, If[17 < o ≤ 18, 18 - o, 0], E_1) → D'_1Segment(D, D'_1) → s_2Rotate(D, If[19 < o ≤ 20, ((-(o - 19)) * π), (-π)], F_1) → D'_2Rotate(M', If[19 < o ≤ 20, ((-(o - 19)) * π), (-π)], F_1) → M''Rotate(B, If[19 < o ≤ 20, ((-(o - 19)) * π), (-π)], F_1) → B'Polygon(D'_2, M'', B') → t6', b', d'_2, m''