Exploring the Area of a Circle by cheredia3

Exploring the Area of a Circle by cheredia3
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2016-04-26 15:13
This example demonstrates how to derive the area of a circle by dissecting it into sectors and rearranging them into a shape resembling a rectangle. Key math concepts include the circumference of a circle, the concept of limits, geometric transformations, and algebraic operations. GeoGebra commands and objects used in the construction include Intersect, Segment, Point, Min, Max, CurveCartesian, Circle, Ray, Midpoint, CircleArc, Sequence, Rotate, Sector, Arc, Textfield. Suitable for high school mathematics instruction to visually understand the derivation process of the circle area formula.

GeoGebra Commands & Parameters

  1. Intersect(xAxis, yAxis) → O
  2. Segment(E, (x(E) + 4, y(E))) → a
  3. Point(a) → F
  4. Min((x(F) - x(E)) / (a / 2), 1) → k
  5. Point(Segment[(0, 1), (6.28319, 1)]) → H
  6. Segment(H, (x(H), 0)) → j
  7. Max((x(F) - x(E)) / (a / 2) - 1, 0) → k'
  8. CurveCartesian(t - sin(t), 1 - cos(t), t, 0, 6.28319) → b
  9. Circle((0, 1), 1) → h
  10. Ray((0, 0), (1, 0)) → i
  11. Midpoint(a) → J
  12. Circle((0, 1), 1) → c_1
  13. Segment((0, 0), (6.28319, 0)) → e
  14. Segment(G, (x(G), y(G) - 1)) → r
  15. CircleArc((0, 1 / (1 - m)), (0, 0), L) → s
  16. Sequence((x(O) + sin((i * θ)), y(O) + 1 - cos((i * θ))), i, 0, (2 * n)) → list1
  17. 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)) → list2
  18. Rotate((x(O) + 0, y(O) + 1), ((-k) * θ / 2), O) → A
  19. Rotate(O, ((-k) * θ / 2), O) → O'
  20. Rotate(Element[list1, 1], ((-k) * θ / 2), O) → B
  21. Sector(Rotate[Circle[(x(O) + 0, y(O) + 1), O], ((-k) * θ / 2), O], Rotate[O, ((-k) * θ / 2), O], Rotate[Element[list1, 1], ((-k) * θ / 2), O]) → c
  22. Rotate((x(O) + 0, y(O) + 1), ((-k) * θ / 2), O) → C
  23. Rotate(Element[list1, 1], ((-k) * θ / 2), O) → D
  24. Rotate(O, ((-k) * θ / 2), O) → O'_1
  25. Arc(Rotate[Circle[(x(O) + 0, y(O) + 1), O], ((-k) * θ / 2), O], O'_1, D) → d
  26. Midpoint(j) → I
  27. Circle(L, 1 / (1 - m)) → p
  28. Circle((0, 0), 1 / (1 - m)) → q
  29. Intersect(p, q, 1) → M
  30. Sequence(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) → list3
  31. Sequence(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)) → list4
  32. Midpoint(e) → N
  33. Textfield() → InputBox1
  34. Textfield() → InputBox2
  35. Point(c_1) → Q
  36. Segment(H, Q) → g

AI Drawing Prompt Reference

Draw a circle with radius 1, divided into many sectors. Rearrange these sectors by rotating and translating them into a shape resembling a rectangle. Include a horizontal segment representing the circumference, a slider to control the number of sectors, and another slider to control the rearrangement progress. When progress is 0, sectors stay in circular arrangement; when progress is 1, they form a rectangle. Also show an auxiliary circle, a radius segment from center to circumference, and two input boxes for parameters. This illustrates the derivation of the circle area formula.
The prompt above was compiled from the original drawing commands and is for reference only.