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数轴上的减法

数轴上的减法
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2015-11-06 05:05
函数解析几何几何作图
①本范例演示在数轴上通过可视化方式展示减法运算的过程；②涉及的核心数学概念包括数轴、实数减法、绝对值运算；③作图要点——从下方『构造摘要』提炼用到了Textfield, Segment, Point, Min, Max, If, Polygon, Midpoint等GeoGebra命令/对象；④适合初中数学教学，帮助学生直观理解减法的几何意义。

GeoGebra 命令及参数

  1. Textfield(Ltext) → InputBox1
  2. Textfield(Rtext) → InputBox2
  3. Segment(A, D) → b
  4. Segment(D, E) → c
  5. Segment(E, B) → d
  6. Point(a) → G
  7. Min(upper, lower) → L
  8. Max(upper, lower) → R
  9. If(x(G) < L - (0.1 * spread), x(A) - spread / 15, If[x(G) > R + (0.1 * spread), x(A) - (0.6 * spread), L - spread / 3]) → left
  10. If(x(G) < L - (0.1 * spread), x(B) + (0.6 * spread), If[x(G) > R + (0.1 * spread), x(B) + spread / 15, R + spread / 3]) → right
  11. Polygon((-1000000, 6), (1000000, 6), (1000000, -6), (-1000000, -6)) → poly1, f, g, h, i
  12. Segment((x(C), 2.5), (x(A), 2.5)) → m
  13. Segment((x(F), 2.5), (x(B), 2.5)) → p
  14. Midpoint(m) → H
  15. Midpoint(p) → I
  16. Segment(C, H) → l
  17. Segment(H, A) → n
  18. Segment(F, I) → q
  19. Segment(I, B) → r
  20. If(x(A) > L, "+", "-") → text2