Circle, Ellipse, and Hyperbola as Envelopes from One Construction

Circle, Ellipse, and Hyperbola as Envelopes from One Construction
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2024-06-08 17:08
In collections History of Maths
This GeoGebra example demonstrates how a single geometric construction can generate a circle, an ellipse, and a hyperbola as envelope/locus curves, enabling direct visual comparison of the three conic types. Key concepts include loci and envelopes, the relationship between tangency and curve generation, and the geometric constraints that define second-degree curves. The construction uses GeoGebra commands such as Polygon, Circle, Point, Segment, and LineBisector to set up baseline geometry, Intersect to compute critical intersection points, Rotate to drive the configuration with a parameter, Tangent to construct tangent lines, OrthogonalLine to impose perpendicular/normal constraints, and finally Hyperbola and Ellipse to display the resulting conic envelopes. It is well-suited for secondary to early university levels, especially for instruction or self-study on analytic geometry, geometric construction, and dynamic visualization of conic properties.

GeoGebra Commands & Parameters

  1. Polygon({(-12, -4.5), (13, -4.5), (13, 8.5), (-12, 8.5)}) → peep
  2. Circle(O, 8) → c
  3. Point(c) → A
  4. Segment((-14, 0), (14, 0)) → domF
  5. Point(domF) → F
  6. Segment(F, A) → g
  7. LineBisector(g) → envel
  8. Intersect(envel, g) → I
  9. Segment(F, I) → f
  10. Segment(I, A) → h
  11. Rotate(F, 90°, I) → F'
  12. Angle(F, I, F') → α
  13. Tangent(A, c) → tgA,
  14. OrthogonalLine(A, tgA) → normA
  15. Intersect(envel, normA) → E
  16. Angle(tgA, normA) → β
  17. Hyperbola(F, O, Radius[c] / 2) → ip
  18. Ellipse(F, O, Radius[c] / 2) → d

AI Drawing Prompt Reference

Draw a figure containing a circle, an ellipse, and a hyperbola. Start by drawing a rectangle, then draw a circle with one of its vertices as the center. Take a point on the circle and draw a tangent line at that point, then construct a line perpendicular to the tangent. Rotate the perpendicular line around the point to form an angle. Use the intersection of the perpendicular line and the tangent to construct the hyperbola and ellipse, and adjust the parameters to observe the changes in the three conic sections.
The prompt above was compiled from the original drawing commands and is for reference only.