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Dandelin Spheres by Irina Boyadzhiev (2)

Dandelin Spheres by Irina Boyadzhiev (2)
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2015-11-02 11:22
CircleSolid GeometryGeometric Construction
In collections Conic Sections
This example demonstrates the concept of Dandelin spheres, where two spheres are tangent to the cone and intersect the plane to determine the conic section. Key concepts include cones, planes, spheres, and their intersections. Commands used include Intersect, Point, Line, Plane, Mirror, Ray, Angle, InfiniteCone, IntersectPath, AngularBisector, OrthogonalLine, Circle, Sphere, Segment, PointIn, OrthogonalPlane, If. Suitable for high school geometry education.

GeoGebra Commands & Parameters

  1. Intersect(xAxis, yAxis) → A
  2. Point(zAxis) → B
  3. Line(C, yAxis) → a
  4. Plane(D, a) → b
  5. Mirror(C, D) → C'
  6. Ray(D, C') → c
  7. Angle(c, zAxis) → δ
  8. InfiniteCone(A, B, aa) → d
  9. IntersectPath(b, xz) → int
  10. IntersectPath(xz, d) → g
  11. Intersect(int, g) → V2, V1
  12. Line(A, V1) → c_1
  13. Line(A, V2) → c_2
  14. Line(A, B) → vert
  15. Point(c_2) → K
  16. IntersectPath(b, d) → r
  17. AngularBisector(c_1, int) → f, i
  18. Intersect(vert, f) → O2
  19. Intersect(vert, i) → O1
  20. OrthogonalLine(O2, c_1, xz) → j
  21. OrthogonalLine(O1, c_1, xz) → k
  22. Intersect(c_1, j) → G
  23. Intersect(c_1, k) → H
  24. Circle(O2, G, xz) → p
  25. Circle(O1, H, xz) → q
  26. Intersect(int, q) → F_1, J
  27. Intersect(int, p) → F_2, M
  28. Sphere(O1, F_1) → l
  29. Sphere(O2, F_2) → m
  30. Circle(zAxis, H) → tan2
  31. Circle(zAxis, G) → tan1
  32. Point(r) → Q
  33. Line(Q, A) → gen
  34. Intersect(gen, tan1) → E,
  35. Intersect(gen, tan2) → F,
  36. Segment(Q, F_2) → e
  37. Segment(Q, F) → n
  38. Segment(Q, F_1) → s
  39. Segment(Q, E) → t
  40. Circle(vert, Q) → d_1
  41. Plane(tan2) → o
  42. IntersectPath(o, b) → dir
  43. OrthogonalLine(Q, dir, b) → a_1
  44. Intersect(dir, a_1) → I
  45. OrthogonalLine(Q, a_1, b) → b_1
  46. Intersect(b_1, int) → L
  47. Intersect(dir, r) → N,
  48. Intersect(int, r) → O, P
  49. Intersect(dir, int) → R
  50. Segment(Q, I) → e_1
  51. Segment(L, R) → f_1
  52. Intersect(b_1, r) → S, T
  53. PointIn(b) → W
  54. OrthogonalPlane(R, dir) → u
  55. IntersectPath(u, d) → g_1
  56. Intersect
  57. Intersect(g_1, tan2) → U, V, ,
  58. Intersect
  59. Intersect(g_1, d_1) → Z, A_1, ,
  60. Segment(Z, U) → h_1
  61. If(bb < aa, text3, If[bb > aa, text1, text2]) → angle
  62. Angle(Q, I, R, b) → α
  63. Point(dir) → B_1
  64. Angle(F_1, R, B_1, b) → β