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Triangle Exterior Angle Theorem Dynamic Demonstration

Triangle Exterior Angle Theorem Dynamic Demonstration
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2016-07-26 21:15
TriangleAngleTransformationGeometric ConstructionSlider Animation
In collections Congruence (CO) Cluster Congruence (Vol 2) CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 Gail LeBlancCCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 CCSS High School: Geometry (Congruence) Volume 2 Triangle Theorems Unit 7: Polygons and Quadrilaterals
① This GeoGebra example dynamically demonstrates the Triangle Exterior Angle Theorem, showing that an exterior angle of a triangle equals the sum of the two non-adjacent interior angles. ② Core mathematical concepts include exterior angles, interior angles, angle measurement, triangle angle sum, and geometric reasoning. ③ Construction highlights: using GeoGebra commands such as Line, Ray, Segment to build the triangle and its extended sides; Angle to mark and measure angles; Point, Intersect, Polygon for basic objects; and Rotate, Translate, Dilate for dynamic transformations. Sliders or draggable points allow changing the triangle shape to verify the theorem holds universally. ④ Suitable for middle school geometry lessons, high school review, and teacher-created interactive materials, as well as student self-exploration of angle relationships in triangles.

GeoGebra Commands & Parameters

  1. Line(A, B) → f
  2. Slope(f) → a
  3. PointIn(c) → C
  4. Segment(A, C) → g
  5. Segment(C, B) → h
  6. Segment(B, A) → i
  7. Min(list1) → d
  8. Circle(A, (0.2 * d)) → e
  9. Circle(B, (0.2 * d)) → k
  10. Circle(C, (0.2 * d)) → p
  11. Ray(A, B) → j
  12. Ray(B, C) → l
  13. Ray(C, A) → m
  14. Point(j) → D
  15. Point(l) → E
  16. Point(m) → F
  17. Ray(B, D) → n
  18. Ray(C, E) → q
  19. Ray(A, F) → r
  20. Intersect(p, g, 1) → G
  21. Intersect(p, h, 1) → H
  22. Intersect(e, i, 1) → I
  23. Intersect(e, g, 1) → J
  24. CircleSector(A, I, J) → s
  25. CircleSector(C, G, H) → t
  26. Polygon(A, B, C) → poly1, c_1, a_1, b_1
  27. Dilate(A, If[0 < o ≤ 1, 1 - o, 0], B) → A'
  28. Vector(A, A') → u
  29. Translate(s, u) → s'
  30. CircleArc(A, I, J) → d_1
  31. Distance(A, I) → v
  32. Rotate(t, If[1 < o ≤ 2, ((o - 1) * pi), pi], C) → t'
  33. CircleArc(C, G, H) → e_1
  34. Angle(G, C, H) → α
  35. Dilate(C, If[2 < o ≤ 3, 3 - o, 0], B) → C'
  36. Vector(C, C') → u_1
  37. Translate(t', u_1) → t''
  38. Intersect(k, n) → K,
  39. Intersect(k, h) → L,
  40. CircleArc(B, K, L) → f_1