动画演示平行四边形与梯形性质
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①本范例通过动画演示平行四边形与梯形的几何性质,特别是角度、中位线与斜率的关系;②涉及核心数学概念包括角度、梯形、斜率差、中位线、比例、双曲线、正方形等;③作图要点运用了Line, Ray, Point, Midpoint, Slope, OrthogonalLine, Mirror, Dilate, Segment, Circle, Intersect, CircleSector, Vector, Translate, Angle, Rotate, Polygon等GeoGebra命令与对象;④适合高中数学教学,用于理解几何变换与性质。
GeoGebra 命令及参数
Line(A, B) → aRay(A, B) → bPoint(b) → CMidpoint(A, C) → DLine(A, C) → cSlope(c) → dOrthogonalLine(D, c) → gPoint(g) → ERay(D, E) → hPoint(h) → FSlope(h) → iLine(F, c) → lPoint(l) → GPoint(l) → HRay(F, G) → mRay(F, H) → nPoint(m) → IMirror(I, h) → I'Dilate(A, If[0 < o ≤ 1, 1 - o, 0], C) → A'Segment(A, A') → pDilate(A, If[1 < o ≤ 2, 2 - o, 0], I) → A'_1Segment(A, A'_1) → qSegment(A, C) → rSegment(C, I') → sSegment(I', I) → tSegment(I, A) → a_1Circle(A, (0.2 * Min[a_1, r])) → c_1Circle(I, (0.2 * Min[a_1, r])) → d_1Intersect(d_1, a_1, 1) → JIntersect(d_1, t, 1) → KIntersect(c_1, r, 1) → LIntersect(c_1, a_1, 1) → MCircleSector(A, L, M) → e_1CircleSector(I, J, K) → f_1Dilate(I, If[2 < o ≤ 3, 3 - o, 0], I') → I'_1Segment(I, I'_1) → b_1Dilate(A, If[3 < o ≤ 4, 4 - o, 0], C) → A'_2Vector(A, A'_2) → uTranslate(A, u) → A'_3Translate(A'_1, u) → NSegment(A'_3, N) → q'OrthogonalLine(A, r) → g_1Point(g_1) → OAngle(I, A, O) → αAngle(I', C, A) → βRotate(A'_3, If[4 < o ≤ 5, (((o - 4) * 2) * α), (2 * α)], C) → PRotate(N, If[4 < o ≤ 5, (((o - 4) * 2) * α), (2 * α)], C) → N'Segment(P, N') → q''Dilate(A, If[5 < o ≤ 6, 6 - o, 0], C) → A'_4Vector(A, A'_4) → vTranslate(e_1, v) → h_1Rotate(h_1, If[6 < o ≤ 7, ((o - 6) * ((2 * α) + β)), (2 * α) + β], C) → k_1Dilate(I, If[7 < o ≤ 8, 8 - o, 0], I') → I'_2Vector(I, I'_2) → wTranslate(f_1, w) → p_1Rotate(p_1, If[8 < o ≤ 9, ((-(o - 8)) * β), (-β)], I') → q_1Dilate(A, If[9 < o ≤ 10, 10 - o, 0], I') → A'_5Segment(A, A'_5) → i_1Dilate(A, If[10 < o ≤ 11, 11 - o, 0], I) → A'_6Vector(A, A'_6) → u_1Translate(A, u_1) → A'_7Translate(A'_5, u_1) → QSegment(A'_7, Q) → j_1Segment(I, C) → l_1Angle(L, A, I') → γRotate(A'_7, If[11 < o ≤ 12, ((-(o - 11)) * (2 * γ)), (-2 * γ)], I) → RRotate(Q, If[11 < o ≤ 12, ((-(o - 11)) * (2 * γ)), (-2 * γ)], I) → Q'Segment(R, Q') → m_1Polygon(A, C, I', I) → poly1, a_2, c_2, i', i_2