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Unwrapping a Cylinder: REVAMPED!

Unwrapping a Cylinder: REVAMPED!
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2020-12-04 23:19
Solid GeometryTransformationParametric EquationGeometric ConstructionSlider Animation
① This example demonstrates the dynamic process of unwrapping the surface of a 3D cylinder onto a 2D plane, showing the correspondence of geometric elements (points, lines, arcs, surfaces) before and after the transformation. ② Core mathematical concepts include solid geometry (cylinder, net, surface-to-plane mapping) and plane geometry (triangles, circles, polygons, angles, vectors). ③ Construction highlights: from the summary, it uses GeoGebra commands such as Cylinder, Line, Intersect, Sphere, Plane, Rotate, Dilate, Vector, Translate, Polygon, Segment, CircleArc, Angle, CurveCartesian, Surface, Midpoint, and Mirror, with many objects (r, h, A, B, C, etc.) to control the unfolding via parameters. ④ Suitable for high school or early college courses in solid geometry and analytic geometry, as well as for mathematical modeling or geometric visualization, helping students intuitively grasp the geometric transformation of cylinder unwrapping.

GeoGebra Commands & Parameters

  1. Cylinder(A, C, r) → a, c, d, b
  2. Line(D, E) → f
  3. Intersect(f, d, 1) → F
  4. Sphere(F, r) → e
  5. Intersect(f, e) → G, H
  6. Plane(G, F, C) → g
  7. Rotate(C, If[0 < i ≤ 1, (i * π / 2), π / 2], D, g) → C'
  8. Rotate(d, If[0 < i ≤ 1, (i * π / 2), π / 2], D, g) → d'
  9. Rotate(dd, If[0 < i ≤ 1, (i * π / 2), π / 2], D, g) → dd'
  10. Dilate(C, If[1 < i ≤ 2, 2 - i, 0], I) → C'_1
  11. Dilate(C, If[1 < i ≤ 2, 2 - i, 0], J) → C'_2
  12. Vector(C, C'_1) → u
  13. Vector(C, C'_2) → v
  14. Translate(dd, u) → dd'_1
  15. Translate(dd, v) → dd'_2
  16. Translate(K, u) → K'
  17. Translate(K, v) → K'_1
  18. Rotate(K', If[1 < i ≤ 2, ((i - 1) * π), π], C'_1) → K''
  19. Rotate(K'_1, If[1 < i ≤ 2, ((-(i - 1)) * π), (-π)], C'_2) → L
  20. Translate(D, u) → D'
  21. Translate(D, v) → D'_1
  22. Polygon(D', D'_1, N, M) → poly1, d'_1, d'_2, n, m
  23. Segment(K'', Q) → j
  24. CircleArc(P, Q, M) → k
  25. Segment(L, S) → l
  26. CircleArc(R, N, S) → p
  27. CircleArc(C'_2, D'_1, L) → q
  28. CircleArc(C'_1, K'', D') → s
  29. Plane(T, A, B) → o
  30. Rotate(C', If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → C''
  31. Rotate(poly1, If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → poly1'
  32. Rotate(d', If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → d'_3
  33. Rotate(dd', If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → dd'_3
  34. Rotate(K'', If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → K'''
  35. Rotate(Q, If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → Q'
  36. Segment(K''', Q') → j'
  37. Rotate(L, If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → L'
  38. Rotate(S, If[2 < i ≤ 3, ((i - 2) * π / 2), π / 2], E, g) → S'
  39. Segment(L', S') → l'
  40. Dilate(C'', If[3 < i ≤ 4, 4 - i, 0], U) → C'''
  41. Vector(C'', C''') → w
  42. Dilate(C'', If[3 < i ≤ 4, 4 - i, 0], V) → C'''_1
  43. Vector(C'', C'''_1) → t
  44. Translate(Z, w) → Z'
  45. Translate(Z, t) → Z'_1
  46. Translate(W, w) → W'
  47. Translate(W, t) → W'_1
  48. Rotate(W', If[3 < i ≤ 4, ((-(i - 3)) * π), (-π)], C''') → W''
  49. CircleArc(C''', Z', W'') → c_1
  50. Segment(Z, Z') → f_1
  51. Rotate(W'_1, If[3 < i ≤ 4, ((i - 3) * π), π], C'''_1) → A_1
  52. CircleArc(C'''_1, Z'_1, A_1) → d_1
  53. Segment(Z, Z'_1) → g_1
  54. Segment(R, N) → h_1
  55. Angle(N, R, S) → α
  56. CurveCartesian(x(C'_2) + (r * cos(t)), y(C'_2) + (r * sin(t)), z(C'_2), t, π / 2, π / 2 + α) → a_1
  57. Vector(A, C) → tt
  58. Surface(x(C'_2) + (r * cos(t)) - (u * x(tt)), y(C'_2) + (r * sin(t)) - (u * y(tt)), z(C'_2) - (u * z(tt)), u, 0, 1, t, π / 2, π / 2 + α) → b_1
  59. Surface((-x(C'_2)) - (r * cos(t)) - (u * x(tt)), y(C'_2) + (r * sin(t)) - (u * y(tt)), z(C'_2) - (u * z(tt)), u, 0, 1, t, π / 2, π / 2 + α) → e_1
  60. Midpoint(L', S') → B_1
  61. Midpoint(K''', Q') → C_1
  62. Line(B_1, C_1) → i_1
  63. Mirror(d_1, i_1) → k_1
  64. Mirror(c_1, i_1) → p_1
  65. Mirror(Z, i_1) → Z'_2
  66. Mirror(Z', i_1) → Z''
  67. Segment(Z'_2, Z'') → j_1
  68. Mirror(Z, i_1) → Z'_3
  69. Mirror(Z'_1, i_1) → D_1
  70. Segment(Z'_3, D_1) → l_1

AI Drawing Prompt Reference

Create a visualization of unwrapping a cylinder into a plane. Build a 3D cylinder from a circular base with a chosen axis/center, mark corresponding points on the cylinder and derive key intersection points using lines and a sphere-based auxiliary intersection. Define a plane through three reference points that will serve as the unfolding sheet. Construct circle arcs, arc segments, and straight segments that represent the cylinder’s boundary pieces and the edges of the net. Then apply successive rotations (by quarter-turn and half-turn type angles) about a fixed point/axis, together with translations to reposition copies so all pieces lie on the same 2D plane and match the intended correspondences. Use additional arcs to connect the unfolded boundary smoothly and include an auxiliary plane view to suggest the before/after mapping.
The prompt above was compiled from the original drawing commands and is for reference only.