向量场的积分:正方形
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①本范例演示了在正方形区域内对向量场进行积分的计算过程;②涉及的核心数学概念包括向量场、积分、导数、曲面积分等;③作图要点使用了GeoGebra的Sequence, Line, Circle, CurveCartesian, Derivative, Sum, Segment, Distance, Textfield等命令和对象;④适合高中及以上学生学习和理解向量场积分的几何意义及计算方法。
GeoGebra 命令及参数
Sequence(Sequence[Vector[(j, k), (j + (scale * F_1(j, k)), k + (scale * F_2(j, k)))], j, xmin, xmax, xstep], k, ymin, ymax, ystep) → vFieldLine(I, xAxis) → fLine(J, xAxis) → gLine(K, xAxis) → hSequence(Segment[Rotate[curlPt - (0.2, 0), k + curlAngle, curlPt], Rotate[curlPt + (0.2, 0), k + curlAngle, curlPt]], k, 0, 2.0944, 1.0472) → spokesCircle(divPt, 0.2) → divGlowCircleCurveCartesian((t * x(Drag)) + ((1 - t) * x(Drag)), (t * (y(Drag) + Side)) + ((1 - t) * y(Drag)), t, 0, 1) → path_{s1}CurveCartesian((t * (x(Drag) - Side)) + ((1 - t) * x(Drag)), (t * (y(Drag) + Side)) + ((1 - t) * (y(Drag) + Side)), t, 0, 1) → path_{s2}CurveCartesian((t * (x(Drag) - Side)) + ((1 - t) * (x(Drag) - Side)), (t * y(Drag)) + ((1 - t) * (y(Drag) + Side)), t, 0, 1) → path_{s3}CurveCartesian((t * x(Drag)) + ((1 - t) * (x(Drag) - Side)), (t * y(Drag)) + ((1 - t) * y(Drag)), t, 0, 1) → path_{s4}Derivative(path_{s1}) → Dpath_{s1}Derivative(path_{s2}) → Dpath_{s2}Derivative(path_{s3}) → Dpath_{s3}Derivative(path_{s4}) → Dpath_{s4}Sum(Sequence[(((F_1(x(path_{s1}(i + dS / 2)), y(path_{s1}(i + dS / 2))), F_2(x(path_{s1}(i + dS / 2)), y(path_{s1}(i + dS / 2)))) * (y(Dpath_{s1}(i + dS / 2)), (-x(Dpath_{s1}(i + dS / 2))))) * dS), i, 0, 1 - dS, dS]) → Flux_{s1}Sum(Sequence[(((F_1(x(path_{s2}(i + dS / 2)), y(path_{s2}(i + dS / 2))), F_2(x(path_{s2}(i + dS / 2)), y(path_{s2}(i + dS / 2)))) * (y(Dpath_{s2}(i + dS / 2)), (-x(Dpath_{s2}(i + dS / 2))))) * dS), i, 0, 1 - dS, dS]) → Flux_{s2}Sum(Sequence[(((F_1(x(path_{s3}(i + dS / 2)), y(path_{s3}(i + dS / 2))), F_2(x(path_{s3}(i + dS / 2)), y(path_{s3}(i + dS / 2)))) * (y(Dpath_{s3}(i + dS / 2)), (-x(Dpath_{s3}(i + dS / 2))))) * dS), i, 0, 1 - dS, dS]) → Flux_{s3}Sum(Sequence[(((F_1(x(path_{s4}(i + dS / 2)), y(path_{s4}(i + dS / 2))), F_2(x(path_{s4}(i + dS / 2)), y(path_{s4}(i + dS / 2)))) * (y(Dpath_{s4}(i + dS / 2)), (-x(Dpath_{s4}(i + dS / 2))))) * dS), i, 0, 1 - dS, dS]) → Flux_{s4}Sum(list1, (s * 4)) → TTSum(Sequence[((path_{s1}(i + dS) - path_{s1}(i)) * (F_1(x(path_{s1}(i + dS / 2)), y(path_{s1}(i + dS / 2))), F_2(x(path_{s1}(i + dS / 2)), y(path_{s1}(i + dS / 2))))), i, 0, s - dS, dS]) → Circ_1Sum(Sequence[((path_{s2}(i + dS) - path_{s2}(i)) * (F_1(x(path_{s2}(i + dS / 2)), y(path_{s2}(i + dS / 2))), F_2(x(path_{s2}(i + dS / 2)), y(path_{s2}(i + dS / 2))))), i, 0, s - dS, dS]) → Circ_2Sum(Sequence[((path_{s3}(i + dS) - path_{s3}(i)) * (F_1(x(path_{s3}(i + dS / 2)), y(path_{s3}(i + dS / 2))), F_2(x(path_{s3}(i + dS / 2)), y(path_{s3}(i + dS / 2))))), i, 0, s - dS, dS]) → Circ_3Sum(Sequence[((path_{s4}(i + dS) - path_{s4}(i)) * (F_1(x(path_{s4}(i + dS / 2)), y(path_{s4}(i + dS / 2))), F_2(x(path_{s4}(i + dS / 2)), y(path_{s4}(i + dS / 2))))), i, 0, s - dS, dS]) → Circ_4Sum(list2, (4 * s)) → TT_2Segment(path_{s1}(0.5), path_{s1}(0.5 + 0.01)) → arrw01Segment(path_{s2}(0.5), path_{s2}(0.5 + 0.01)) → arrw02Segment(path_{s3}(0.5), path_{s3}(0.5 + 0.01)) → arrw03Segment(path_{s4}(0.5), path_{s4}(0.5 + 0.01)) → arrw04Distance(Drag, (0, 0)) → condTextfield(F_1) → InputBox1Textfield(F_2) → InputBox2