Approximation of Pi by Inscribed and Circumscribed Polygons

Approximation of Pi by Inscribed and Circumscribed Polygons
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2014-01-31 05:32
① This example dynamically demonstrates how the areas of an inscribed polygon and a circumscribed polygon around a circle approach the circle's area as the number of sides n increases, thereby approximating the value of π. ② Core mathematical concepts include pi, polygon area, the concept of limits, and the squeeze theorem (sandwich theorem) — as n grows, the inscribed area increases from below and the circumscribed area decreases from above, both converging to the circle's area and bounding π. ③ Construction details: using GeoGebra commands such as Circle to draw the circle, Intersect to find intersection points, Sequence to generate vertex lists, Polygon to construct the inscribed polygon (poly1) and circumscribed polygon (poly2), Area to compute areas, and a slider n to control the number of sides; text objects (text1, text2) display the computed areas and the resulting approximation of π. ④ Suitable for high school or early college students learning limits and numerical approximation of π, as well as for math lab activities or inquiry-based learning to illustrate the idea of approximating curved shapes with polygons.

GeoGebra Commands & Parameters

  1. Circle(A, 1) → c
  2. Intersect(c, xAxis, 2) → B
  3. Sequence(Tangent[Rotate[B, ((2 * i) * 3.141592653589793 / n), A], c], i, 1, n + 1) → list1
  4. Sequence(Intersect[Element[list1, j], Element[list1, j + 1]], j, 1, n) → list2
  5. Polygon(list2) → poly1, , ,
  6. Sequence(Rotate[B, ((2 * i) * π / n), A], i, 1, n + 1) → list3
  7. Polygon(list3) → poly2, , , ,
  8. Area(c) → a

AI Drawing Prompt Reference

Draw a unit circle centered at the origin. Mark a starting point on the circle. By rotating this point repeatedly, generate a sequence of vertices equally spaced around the circle, and connect them in order to form an inscribed regular polygon. At each vertex, draw a tangent line to the circle; adjacent tangents intersect, producing a set of intersection points. Connect these points to form a circumscribed polygon around the circle. Use a slider to control the number of sides. As the side count increases, the inscribed polygon's area approaches the circle's area from below, while the circumscribed polygon's area approaches from above. Display the computed areas of both polygons and the resulting approximation of pi, illustrating the squeeze theorem visually.
The prompt above was compiled from the original drawing commands and is for reference only.