直角三角形奇观:如何证明?
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该范例通过 GeoGebra 动态作图直观演示直角三角形的几何性质与证明思路。核心数学概念涵盖直角三角形、角度关系、多边形构造、圆与圆扇、旋转与缩放等相似变换,以及点、线、圆的交点运算。作图要点:调用了 Point、Segment、Polygon、Angle、Circle、CircleSector、Intersect、Rotate、Dilate、Midpoint、Line、Ray、Min 等命令,并使用了 A、B、C、D、E、F、G、H 等点对象、α、β、γ、δ 等角度量,以及 poly1、c、c_1 等图形对象。适合初中至高中平面几何教学,可用于课堂演示、学生自主探究和几何证明辅助。
GeoGebra 命令及参数
Intersect(xAxis, yAxis) → APoint(Ray[(0, 0), (1, 0)]) → BPoint(Ray[(0, 0), (0, 1)]) → CPolygon(A, B, C) → t1, c, a, bSegment(C, A) → fSegment(A, B) → gSegment(B, C) → hPolygon(C, B, 4) → poly1, i, j, k, l, D, ERotate(B, 45°, A) → B'Angle(B, A, B') → αRay(A, B') → mLine(E, D) → nIntersect(n, m) → FIntersect(h, m) → GPolygon(C, G, F, E) → q1, c_1, g_1, f_1, eMidpoint(G, F) → HSegment(B, D) → pSegment(D, E) → qSegment(E, C) → rAngle(C, E, D) → βAngle(E, D, B) → γAngle(D, B, C) → δDilate(A, If[0 < d ≤ 1, 1 - d, 0], G) → A'Segment(A, A') → sDilate(G, If[1 < d ≤ 2, 2 - d, 0], F) → G'Segment(G, G') → tMin(g, f) → oCircle(A, (0.5 * o)) → d_1Intersect(d_1, g, 1) → IRotate(I, If[3 < d ≤ 4, ((d - 3) * π / 4), π / 4], A) → I'CircleSector(A, I, I') → e_1Rotate(e_1, If[5 < d ≤ 6, ((d - 5) * π / 4), π / 4], A) → h_1Rotate(C, If[7 < d ≤ 8, ((-(d - 7)) * π), π], H) → C'Rotate(G, If[7 < d ≤ 8, ((-(d - 7)) * π), π], H) → G'_1Rotate(F, If[7 < d ≤ 8, ((-(d - 7)) * π), π], H) → F'Rotate(E, If[7 < d ≤ 8, ((-(d - 7)) * π), π], H) → E'Polygon(C', G'_1, F', E') → q1', c', g'_1, f', e'Angle(B, A, C) → εRay((0, 0), (1, 0)) → i_1Ray((0, 0), (0, 1)) → j_1