Proof Without Words: Isosceles Triangle Base Midpoint Property

Proof Without Words: Isosceles Triangle Base Midpoint Property
Loading the math board and drawing, please wait…
2020-01-27 17:59
This example demonstrates the property of the midpoint of the base of an isosceles triangle by dragging points. It proves that the distances from the midpoint to the two legs of the isosceles triangle are equal. By constructing midpoints, mirrors, semicircles, and other geometric objects, the property is visually demonstrated. Suitable for junior high school geometry.

GeoGebra Commands & Parameters

  1. Intersect(xAxis, yAxis) → A
  2. Point(xAxis) → B
  3. Ray(A, B) → a
  4. Point(a) → C
  5. Mirror(C, A) → C'
  6. Semicircle(C, C') → c
  7. Intersect(c, yAxis) → D,
  8. CircleArc(A, D, C) → d
  9. Point(d) → E
  10. Segment(C, E) → b
  11. Segment(E, C') → e
  12. Segment(C', C) → f
  13. Polygon(C', C, 4) → poly1, g, h, i, j, F, G
  14. Polygon(C, E, 4) → poly2, k, l, m, n, H, I
  15. Polygon(E, C', 4) → poly3, p, q, r, s, J, K
  16. Midpoint(E, J) → L
  17. OrthogonalLine(L, i) → t
  18. OrthogonalLine(L, t) → a_1
  19. Intersect(a_1, s) → M
  20. Intersect(t, r) → N
  21. Intersect(a_1, q) → O
  22. Intersect(t, e) → P
  23. Polygon(M, L, N, K) → poly4, m_1, l_1, n_1, k_1
  24. Polygon(L, N, J, O) → poly5, l_2, n_2, j_1, o
  25. Polygon(L, P, C', O) → poly6, l_3, p_1, c', o_1
  26. Polygon(P, L, M, E) → poly7, p_2, l_4, m_2, e_1
  27. Vector(L, C) → u
  28. Vector(L, F) → v
  29. Vector(L, C') → w
  30. Vector(L, G) → u_1
  31. Centroid(poly4) → Q
  32. Centroid(poly5) → R
  33. Centroid(poly6) → S
  34. Centroid(poly7) → T
  35. Translate(T, w) → T'
  36. Translate(S, u) → S'
  37. Translate(R, v) → R'
  38. Translate(Q, u_1) → Q'
  39. Segment(Q, Q') → b_1
  40. Segment(R, R') → c_1
  41. Segment(S, S') → d_1
  42. Segment(T, T') → f_1
  43. Point(b_1) → U
  44. Point(c_1) → V
  45. Point(d_1) → W
  46. Point(f_1) → Z
  47. Vector(Q, U) → v_1
  48. Vector(R, V) → w_1
  49. Vector(S, W) → g_1
  50. Vector(T, Z) → h_1
  51. Translate(L, w_1) → L'
  52. Translate(N, w_1) → N'
  53. Translate(J, w_1) → J'
  54. Translate(O, w_1) → O'
  55. Polygon(L', N', J', O') → poly5', l', n', j', o'
  56. Translate(M, v_1) → M'
  57. Translate(L, v_1) → L'_1
  58. Translate(N, v_1) → N'_1
  59. Translate(K, v_1) → K'
  60. Polygon(M', L'_1, N'_1, K') → poly4', m', l'_1, n'_1, k'
  61. Translate(L, g_1) → L'_2
  62. Translate(P, g_1) → P'
  63. Translate(C', g_1) → C''
  64. Translate(O, g_1) → O'_1
  65. Polygon(L'_2, P', C'', O'_1) → poly6', l'_2, p', c'', o'_1
  66. Translate(P, h_1) → P'_1
  67. Translate(L, h_1) → L'_3
  68. Translate(M, h_1) → M'_1
  69. Translate(E, h_1) → E'
  70. Polygon(P'_1, L'_3, M'_1, E') → poly7', p'_1, l'_3, m'_1, e'
  71. Midpoint(H, C) → A_1
  72. Midpoint(C, G) → B_1
  73. Segment(A_1, B_1) → i_1
  74. Point(i_1) → C_1
  75. Vector(A_1, C_1) → q_1
  76. Translate(poly2, q_1) → poly2'

AI Drawing Prompt Reference

Draw an isosceles triangle to demonstrate the property of the midpoint of its base. Show that the distances from the midpoint to the two legs are equal by dragging points. Construct midpoints, mirrors, semicircles, and other geometric objects to visually prove the property. Start by plotting the intersection of axes, then create a ray and point to form the triangle. Draw a semicircle and arc, then segments from the midpoint to the legs. Build several quadrilaterals, find midpoints, draw perpendicular lines and segments, and translate centroids to show equal distances from the midpoint to the legs.
The prompt above was compiled from the original drawing commands and is for reference only.