球面二次曲线构造
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①本范例演示球面二次曲线的构造与性质;②涉及复数、自然数、台形、三角法、放物线等核心数学概念;③通过GeoGebra命令Intersect(交集)、Sphere(球体)、Segment(线段)、Point(点)、Rotate(旋转)、RemoveUndefined(移除未定义对象)、PolyLine(多段线)、CircleArc(圆弧)、If(条件判断)等实现;④适合高中及以上数学学习者和教师用于教学演示与探索。
GeoGebra 命令及参数
Intersect(xAxis, zAxis) → ASphere(A, 1) → aSegment((1.5, -1.5, 0), (1.5, -0.5, 0)) → fSegment((1.5, 1.5, 0), (1.5, 0.5, 0)) → gPoint(f) → BPoint(g) → CRotate((1, 0), θ) → DRotate((1, 0), (-θ)) → ERemoveUndefined(If[(2 * θ) + ϕ < (2 * π), Sequence[If[r > 0, Intersect[Circle[(cos(abs(r)) * D), abs(sin(abs(r))), Vector[D]], Circle[(cos(ϕ - abs(r)) * E), abs(sin(ϕ - abs(r))), Vector[E]], 1], Intersect[Circle[(cos(abs(r)) * D), abs(sin(abs(r))), Vector[D]], Circle[(cos(ϕ - abs(r)) * E), abs(sin(ϕ - abs(r))), Vector[E]], 2]], r, (-ϕ), ϕ, π / 360], Sequence[If[r > 0, Intersect[Circle[(cos(abs(r)) * D), abs(sin(abs(r))), Vector[D]], Circle[(cos(ϕ - abs(r)) * E), abs(sin(ϕ - abs(r))), Vector[E]], 1], Intersect[Circle[(cos(abs(r)) * D), abs(sin(abs(r))), Vector[D]], Circle[(cos(ϕ - abs(r)) * E), abs(sin(ϕ - abs(r))), Vector[E]], 2]], r, ((-ϕ)) / 2, ϕ / 2, π / 180]]) → list1PolyLine(list1) → hPoint(h) → FCircleArc(A, D, F) → cIf((2 * θ) + ϕ < (2 * π), CircleArc[A, E, F], CircumcircleArc[E, (-E), F]) → dRemoveUndefined(Sequence[If[r > 0, Intersect[Circle[(cos(ϕ - abs(r)) * D), abs(sin(ϕ - abs(r))), Vector[D]], Circle[(cos(abs(r)) * E), abs(sin(abs(r))), Vector[E]], 1], Intersect[Circle[(cos(ϕ - abs(r)) * D), abs(sin(ϕ - abs(r))), Vector[D]], Circle[(cos(abs(r)) * E), abs(sin(abs(r))), Vector[E]], 2]], r, ((-ϕ)) / 2, ϕ / 2, π / 180]) → list2PolyLine(list2) → i