圆锥曲面面积计算 by Anthony OR 柯志明
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①本范例演示圆锥曲面面积的计算方法;②涉及核心数学概念包括圆锥几何性质、圆周率π、曲面面积公式;③作图要点——使用Point, If, Sequence, Segment, Min, Max, CircleArc, Midpoint, CircleSector, Circle等GeoGebra命令/对象构建圆锥模型并计算曲面面积;④适合高中数学教学和几何学习,帮助学生理解曲面面积计算原理。
GeoGebra 命令及参数
Point(CircleArc[(0, 1), (1, 1), (0, 0)]) → AIf(y(A) > 0, Angle[(0, 0), (0, 1), A], 6.283185307179586) → αSequence((sin(i * θ), 1 - cos(i * θ)), i, 0, 2 * n) → list1Segment(E, (x(E) + 1, y(E))) → aPoint(a) → FMin(2 * (x(F) - x(E)), 1) → kMax(2 * (x(F) - x(E)) - 1, 0) → k'Sequence(If[k < 1, (x(O) + l * sin(i * φ) * cos(i * φ) / sin(φ), y(O) + l * sin(i * φ) * sin(i * φ) / sin(φ)), (x(O) + l * i, y(O))], i, 0, 2 * n) → list2Sequence(Sector[Rotate[Translate[Circle[(x(O) + 0, y(O) + 1), Element[list1, i]], Vector[Element[list1, i], Element[list2, i]]], -(2 * i - 1) * k * θ / 2, Element[list2, i]], Rotate[Translate[Element[list1, i], Vector[Element[list1, i], Element[list2, i]]], -(2 * i - 1) * k * θ / 2, Element[list2, i]], Rotate[Translate[Element[list1, i + 1], Vector[Element[list1, i], Element[list2, i]]], -(2 * i - 1) * k * θ / 2, Element[list2, i]]], i, 1, n) → list3Sequence(Sector[Rotate[Rotate[Translate[Circle[(x(O) + 0, y(O) + 1), Element[list1, i]], Vector[Element[list1, i], Element[list2, i]]], -(2 * i - 1) * k * θ / 2, Element[list2, i]], 180° * k', (x(O) + n * l - sin(θ / 2) / 2, y(O) + cos(θ / 2) / 2)], Rotate[Rotate[Translate[Element[list1, i], Vector[Element[list1, i], Element[list2, i]]], -(2 * i - 1) * k * θ / 2, Element[list2, i]], 180° * k', (x(O) + n * l - sin(θ / 2) / 2, y(O) + cos(θ / 2) / 2)], Rotate[Rotate[Translate[Element[list1, i + 1], Vector[Element[list1, i], Element[list2, i]]], -(2 * i - 1) * k * θ / 2, Element[list2, i]], 180° * k', (x(O) + n * l - sin(θ / 2) / 2, y(O) + cos(θ / 2) / 2)]], i, n + 1, 2 * n) → list4If(y(A) > 0, CircleArc[(0, 1), (0, 0), A], 6.283185307179586) → sCircleArc((0, 1 / (1 - m)), O, L) → bSegment((0, 0), (s, 0)) → dMidpoint(d) → B'CircleArc((0, 1), A, (0, 0)) → cMidpoint(a) → CPoint(Segment[(0, 1), (s, 1)]) → DSegment(D, (x(D), y(D) - 1)) → eMidpoint(e) → GCircleSector((0, 1), (0, 0), A) → fCircle((0, 1), 1) → gMidpoint(A, D) → H