Law of Sines: Intro via Areas

Law of Sines: Intro via Areas
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2022-01-17 05:10
This example demonstrates the Law of Sines using the area method, involving core concepts like the Law of Sines, triangle area formulas, and the relationship between circles and angles. Construction highlights include using GeoGebra commands like Intersect, Circle, Rotate, Segment to build triangles and angles, and transformations with Dilate and Translate. Suitable for high school students learning trigonometry and geometry.

GeoGebra Commands & Parameters

  1. Intersect(xAxis, yAxis) → A
  2. Circle(A, 1) → c
  3. Rotate((1, 0), (a * π / 180), A) → B
  4. Rotate(D, (a * π / 180), C) → D'
  5. Ray(C, D') → f
  6. Segment(C, D) → g
  7. Rotate(C, ((-b) * π / 180), D) → C'
  8. Ray(D, C') → h
  9. Intersect(f, h) → E
  10. Segment(C, E) → i
  11. Segment(E, D) → j
  12. Rotate((-1, 0), ((-b) * π / 180), A) → F
  13. Segment(A, B) → k
  14. Segment(A, F) → l
  15. Min({1, i, g, j}) → d
  16. Circle(C, (0.45 * d)) → e
  17. Circle(E, (0.45 * d)) → p
  18. Circle(D, (0.45 * d)) → q
  19. Intersect(e, g, 1) → G
  20. Intersect(e, i, 1) → H
  21. Intersect(p, j, 1) → I
  22. Intersect(p, i, 1) → J
  23. Intersect(q, g, 1) → K
  24. Intersect(q, j) → L,
  25. CircleSector(C, G, H) → r
  26. CircleSector(D, L, K) → t
  27. Line(C, xAxis) → m
  28. Point(m) → M
  29. Angle(M, C, G) → α
  30. Dilate(C, If[0 < n ≤ 1, 1 - n, 0], A) → C'_{1}
  31. Vector(C, C'_{1}) → u
  32. Translate(r, u) → r'
  33. Rotate(r', If[0 < n ≤ 1, ((-n) * α), (-α)], C'_{1}) → r''
  34. Line(D, xAxis) → f_1
  35. Point(f_1) → N
  36. Angle(N, D, K) → β
  37. Dilate(D, If[1 < n ≤ 2, 2 - n, 0], A) → D'_{1}
  38. Vector(D, D'_{1}) → v
  39. Translate(t, v) → t'
  40. Rotate(t', If[1 < n ≤ 2, ((-β) * (n - 1)), (-β)], D'_{1}) → t''
  41. Dilate(B, If[2 < n ≤ 3, 3 - n, 0], O) → B'
  42. Dilate(F, If[2 < n ≤ 3, 3 - n, 0], P) → F'
  43. Segment(B, B') → g_1
  44. Segment(F, F') → h_1
  45. Angle(B, O, A) → γ
  46. Angle(A, P, F) → δ
  47. Dilate(B, If[4 < n ≤ 5, 5 - n, 0], E) → B'_{1}
  48. Vector(B, B'_{1}) → u_1
  49. Translate(B, u_1) → B'_{2}
  50. Translate(B', u_1) → B''
  51. Segment(B'_{2}, B'') → i_1
  52. OrthogonalLine(E, i) → j_1
  53. Line(E, g_1) → k_1
  54. Point(j_1) → Q
  55. Point(k_1) → R
  56. Angle(Q, E, R) → ε
  57. Rotate(B'_{2}, If[4 < n ≤ 5, ((-(n - 4)) * ε), (-ε)], B'_{2}) → S
  58. Rotate(B'', If[4 < n ≤ 5, ((-(n - 4)) * ε), (-ε)], B'_{2}) → B'''
  59. Segment(S, B''') → l_1
  60. Angle(Q, E, C) → ζ
  61. Dilate(E, If[5 < n ≤ 6, 6 - n, 0], B''') → E'
  62. Vector(E, E') → v_1
  63. Translate(C, v_1) → C'_{2}
  64. Translate(E, v_1) → E'_{1}
  65. Segment(C'_{2}, E'_{1}) → i'
  66. Angle(E, C, C'_{2}) → η
  67. Dilate(E, If[6 < n ≤ 7, 7 - n, 0], C) → E'_{2}
  68. Vector(E, E'_{2}) → w_1
  69. Translate(S, w_1) → S'
  70. Translate(B''', w_1) → T
  71. Segment(S', T) → m_1
  72. Dilate(P, If[8 < n ≤ 9, 9 - n, 0], D) → P'
  73. Vector(P, P') → a_1
  74. Translate(F, a_1) → F'_{1}
  75. Translate(F', a_1) → F''
  76. Segment(F'_{1}, F'') → n_1
  77. OrthogonalLine(D, j) → p_1
  78. Line(D, h_1) → q_1
  79. Point(q_1) → U
  80. Point(p_1) → V
  81. Angle(U, D, V) → θ
  82. Rotate(F'_{1}, If[8 < n ≤ 9, ((n - 8) * θ), θ], F'') → W
  83. Rotate(F'', If[8 < n ≤ 9, ((n - 8) * θ), θ], F'') → F'''
  84. Segment(W, F''') → r_1
  85. Angle(W, D, E) → ι
  86. Dilate(D, If[9 < n ≤ 10, 10 - n, 0], E) → D'_{2}
  87. Vector(D, D'_{2}) → b_1
  88. Translate(W, b_1) → W'
  89. Translate(F''', b_1) → Z
  90. Segment(W', Z) → s_1
  91. Angle(D, E, W') → κ
  92. Dilate(E, If[10 < n ≤ 11, 11 - n, 0], W') → E'_{3}
  93. Vector(E, E'_{3}) → c_1
  94. Translate(E, c_1) → E'_{4}
  95. Translate(D, c_1) → D'_{3}
  96. Segment(E'_{4}, D'_{3}) → j'
  97. Polygon(D, W, W', E) → q1, d_1, w_2, w', e_1
  98. Circle(D, i) → t_1
  99. Ray(W, W') → f_2
  100. Intersect(t_1, f_2) → A_1,
  101. Dilate(W, If[13 < n ≤ 14, 14 - n, 0], A_1) → W'_{1}
  102. Vector(W, W'_{1}) → u_2
  103. Translate(W', u_2) → W''
  104. Polygon(D, W'_{1}, W'', E) → q2, d_2, w'_{1}, w'', e_2
  105. Line(A_1, D) → g_2
  106. Line(W'', E) → i_2
  107. OrthogonalLine(D, g_2) → h_2
  108. Intersect(i_2, h_2) → B_1
  109. Dilate(E, If[15 < n ≤ 16, 16 - n, 0], B_1) → E'_{5}
  110. Vector(E, E'_{5}) → v_2
  111. Translate(W'', v_2) → W'''
  112. Polygon(D, W'_{1}, W''', E'_{5}) → q3, d_3, j_2, w''', e'_{5}
  113. Dilate(W''', If[17 < n ≤ 18, 18 - n, 0], B''') → C_1
  114. Vector(W''', C_1) → a_2
  115. Translate(D, a_2) → D'_{4}
  116. Translate(W'_{1}, a_2) → D_1
  117. Translate(W''', a_2) → E_1
  118. Translate(E'_{5}, a_2) → F_1
  119. Polygon(D'_{4}, D_1, E_1, F_1) → q3', d'_{4}, k_2, l_2, m_2
  120. Line(B''', g_2) → n_2
  121. Point(n_2) → G_1
  122. Angle(C'_{2}, B''', G_1) → λ
  123. Rotate(D'_{4}, If[17 < n ≤ 18, ((-(n - 17)) * λ), (-λ)], E_1) → H_1
  124. Rotate(D_1, If[17 < n ≤ 18, ((-(n - 17)) * λ), (-λ)], E_1) → I_1
  125. Rotate(E_1, If[17 < n ≤ 18, ((-(n - 17)) * λ), (-λ)], E_1) → J_1
  126. Rotate(F_1, If[17 < n ≤ 18, ((-(n - 17)) * λ), (-λ)], E_1) → K_1
  127. Polygon(H_1, I_1, J_1, K_1) → q3'', p_2, q_2, r_2, s_2
  128. Line(W', W) → t_2
  129. Line(E, D) → b_2
  130. Line(W'_{1}, D) → c_2
  131. Line(W''', E) → f_3
  132. Segment((-1, 0), (1, 0)) → s
  133. Point(c) → L_1
  134. Segment((0, 0), L_1) → g_3

AI Drawing Prompt Reference

In a coordinate plane, use the axes with the origin as reference. Draw two perpendicular axes and a circle centered at a chosen reference point with radius 1. From that center, rotate to place corresponding points on the circle and connect them to form a triangle; use rays along relevant directions to create intersection points. Using a shared scale factor based on the minimal among key segment lengths, draw three circles with equal scaled radii around three triangle vertices, then compute their intersections with the previously constructed segments/lines to obtain several additional points. Construct two circle-sector regions at the appropriate vertices using those intersection points, and add angle markings at key intersections to highlight the area-based relationship underlying the Law of Sines.
The prompt above was compiled from the original drawing commands and is for reference only.