Geometric Transformations with Circular Arcs: Rotations and Mirrors Build Angle

Geometric Transformations with Circular Arcs: Rotations and Mirrors Build Angle
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2024-01-24 02:43
This example demonstrates how to construct a planar geometric configuration where rotations, reflections, and circular arcs create a structured set of angle-and-segment relationships. Key concepts include geometric transformations (Rotate, Mirror, Dilate, Translate), circle geometry (Circle and CircleArc), line constructions and intersection (Line, Intersect, OrthogonalLine), and angle measurement/verification (Angle) together with segment constraints (Segment). Construction highlights: apply Rotate to generate new points from existing ones, use Mirror for symmetric copies, generate boundary curves via Circle and CircleArc, establish helper lines with Line/Ray and perpendiculars using OrthogonalLine, then compute decisive intersection points with Intersect to define the final structure. Finally, use Angle to label and check the intended angular relationships, optionally refining with Vector plus Dilate/Translate to control direction and scale. Suitable for middle-school geometry practice, transformation-focused lessons, and advanced geometry modeling in GeoGebra.

GeoGebra Commands & Parameters

  1. Rotate(N, If[1 < a ≤ 2, (-(a - 1)), -1], M) → N'
  2. CircleArc(M, N', N) → c
  3. Mirror(c, yAxis) → c'
  4. Rotate(C, If[1 < a ≤ 2, (-(a - 1)), -1], N') → C'
  5. Rotate(C', -2, M) → C''_{1}
  6. Rotate(C''_{1}, -2, M) → O
  7. Line(O, C''_{1}) → t
  8. Line(M, t) → g_1
  9. Intersect(c', g_1) → H,
  10. Line(C', C''_{1}) → h
  11. Line(M, h) → i
  12. Intersect(c, i, 1) → D
  13. Angle(D, M, H) → β
  14. Rotate(D, If[5 < a ≤ 6, ((a - 5) * β), β], M) → D'
  15. Mirror(D', M) → D''
  16. Segment(D', D'') → s_1
  17. Circle(H, s_1 / 7) → t_1
  18. Intersect(t_1, s_1, 1) → R
  19. Mirror(H, R) → H'
  20. Mirror(R, H') → R'
  21. Mirror(H', R') → H''
  22. Mirror(C', yAxis) → C''
  23. Line(M, C'') → n_2
  24. OrthogonalLine(C'', n_2) → p_2
  25. Line(M, p_2) → q_2
  26. Point(q_2) → U
  27. Segment(((-r), 0), (r, 0)) → f
  28. Rotate(B, If[7.5 < a ≤ 8.5, ((-(a - 7.5)) * 2), -2], (0, 0)) → B'_{2}
  29. Line((0, 0), B'_{2}) → b
  30. OrthogonalLine(B'_{2}, b) → f_1
  31. Circle((0, 0), r) → d_1
  32. Vector(I, J) → v
  33. Rotate((r, 0), 1, (0, 0)) → K
  34. Rotate((r, 0), 3, (0, 0)) → L
  35. Mirror(K, y = 0) → K'
  36. Dilate(M, If[0 < a ≤ 1, 1 - a, 0], N) → M'
  37. Vector(M, M') → w
  38. Translate(f, w) → f'_{2}
  39. Mirror(N', yAxis) → N''
  40. Mirror(A, yAxis) → A'
  41. Circle(N', r - c) → d
  42. Segment(N', C') → g
  43. Mirror(N', yAxis) → N''_{1}
  44. Segment(N''_{1}, C'') → g'
  45. Rotate(C', -1, M) → C''_{2}
  46. Angle(B, M, D) → α
  47. Rotate(B, If[2 < a ≤ 3, ((a - 2) * α), α], M) → B'
  48. Mirror(B', M) → B''
  49. Segment(B'', B') → j
  50. Dilate(M, If[3 < a ≤ 4, 4 - a, 0], C''_{2}) → M'_{1}
  51. Vector(M, M'_{1}) → u
  52. Translate(B'', u) → B'''
  53. Translate(B', u) → B''_{1}
  54. Segment(B''', B''_{1}) → j'
  55. Rotate(C''_{2}, If[4 < a ≤ 5, a - 4, 1], M) → E
  56. Rotate(C''_{2}, If[4 < a ≤ 5, (-(a - 4)), -1], M) → F
  57. CircleArc(M, C''_{2}, E) → e
  58. CircleArc(M, F, C''_{2}) → k
  59. Circle(E, j / 2 - e) → p
  60. Line(M, E) → l
  61. OrthogonalLine(E, l) → m
  62. Rotate(M, ((-pi)) / 2, E) → M'_{2}
  63. Ray(E, M'_{2}) → n
  64. Intersect(p, n, 1) → G
  65. Rotate(M, pi / 2, E) → M'_{3}
  66. Segment(E, G) → q
  67. Line(M, C''_{2}) → s
  68. Mirror(E, s) → E'
  69. Mirror(G, s) → G'
  70. Segment(E', G') → q'
  71. Rotate(C''_{1}, -1, M) → P
  72. Segment(D', D'') → h_1
  73. Dilate(M, If[6 < a ≤ 7, 7 - a, 0], P) → M'_{4}
  74. Vector(M, M'_{4}) → u_1
  75. Translate(D', u_1) → D''_{1}
  76. Translate(D'', u_1) → D'''
  77. Segment(D''_{1}, D''') → i_1
  78. Rotate(P, If[7 < a ≤ 8, a - 7, 1], M) → P'
  79. Line(M, P) → j_1
  80. Mirror(P', j_1) → P''
  81. CircleArc(M, P, P') → c_1
  82. CircleArc(M, P'', P) → e_1
  83. Circle(P', h_1 / 2 - c_1) → k_1
  84. Circle(P'', h_1 / 2 - c_1) → p_1
  85. Line(M, P') → l_1
  86. OrthogonalLine(P', l_1) → m_1
  87. Rotate(M, ((-pi)) / 2, P') → M'_{5}
  88. Ray(P', M'_{5}) → n_1
  89. Intersect(k_1, n_1) → Q,
  90. Segment(P', Q) → q_1
  91. Mirror(Q, j_1) → Q'
  92. Segment(P'', Q') → r_1
  93. Mirror(R', H'') → R''
  94. Mirror(H'', R'') → H'''
  95. Mirror(R'', H''') → R'''
  96. Dilate(H, If[8 < a ≤ 9, 9 - a, 0], R) → H'_{1}
  97. Segment(H, H'_{1}) → a_1
  98. Rotate(H, If[9 < a ≤ 10, ((a - 9) * pi), pi], R) → H'_{2}
  99. Segment(R, H'_{2}) → b_1
  100. Rotate(R, If[10 < a ≤ 11, ((a - 10) * pi), pi], H') → R'_{1}
  101. Segment(H', R'_{1}) → f_2
  102. Rotate(H', If[11 < a ≤ 12, ((a - 11) * pi), pi], R') → H''_{1}
  103. Segment(R', H''_{1}) → g_2
  104. Rotate(R', If[12 < a ≤ 13, ((a - 12) * pi), pi], H'') → R''_{1}
  105. Segment(H'', R''_{1}) → h_2
  106. Rotate(H'', If[13 < a ≤ 14, ((a - 13) * pi), pi], R'') → H'''_{1}
  107. Segment(R'', H'''_{1}) → i_2
  108. Rotate(R'', If[14 < a ≤ 15, ((a - 14) * pi), pi], H''') → R'''_{1}
  109. Segment(H''', R'''_{1}) → j_2
  110. Line(M, C'') → k_2
  111. Angle(U, M, H'') → γ
  112. Dilate(H'', If[15.5 < a ≤ 16.5, 16.5 - a, 0], C'') → H'''_{2}
  113. Vector(H'', H'''_{2}) → v_1
  114. Dilate(R', If[15.5 < a ≤ 16.5, 16.5 - a, 0], C'') → R''_{2}
  115. Vector(R', R''_{2}) → w_1
  116. Translate(R', w_1) → R''_{3}
  117. Translate(H''_{1}, w_1) → S
  118. Segment(R''_{3}, S) → l_2
  119. Rotate(R''_{3}, If[15.5 < a ≤ 16.5, ((-(a - 15.5)) * γ), (-γ)], R''_{2}) → T
  120. Rotate(S, If[15.5 < a ≤ 16.5, ((-(a - 15.5)) * γ), (-γ)], R''_{2}) → S'
  121. Segment(T, S') → m_2
  122. Rotate(C'', If[16.5 < a ≤ 17.5, ((a - 16.5) * 0.28), 0.28], M) → C'''
  123. CircleArc(M, C'', C''') → c_2
  124. Circle(C''', (0.14 * s_1) - c_2) → d_2
  125. Line(C''', M) → r_2
  126. OrthogonalLine(C''', r_2) → s_2
  127. Rotate(M, ((-pi)) / 2, C''') → M'_{6}
  128. Ray(C''', M'_{6}) → t_2
  129. Intersect(d_2, t_2, 1) → V
  130. Segment(C''', V) → a_2
  131. If(8 < a ≤ 15, 0.75, 0.25) → o_1

AI Drawing Prompt Reference

Construct a planar geometry figure based on rotations, reflections, and circular arcs. Start with a given center point M and a reference line, rotate point N around M to obtain N′, then define a circular arc c using M, N′, and the original point N. Mirror this arc across the y-axis to get c′, and continue generating additional rotated/mirrored arc-related points around M. Draw several auxiliary lines to intersect the mirrored arc and obtain key intersection points H and D. Measure the angle formed by rays from D toward M and H (labeled β), then use that measured angle to rotate D to a new point D′. Mirror D′ across M to form a symmetric pair and connect them to set a segment used as the basis for a circle centered at H. Add further construction using perpendicular lines, additional rotations of points around the origin, and mirror operations to complete the structured configuration with angle labels such as α and β.
The prompt above was compiled from the original drawing commands and is for reference only.