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Sum of Angles in a Triangle by Terry Lee Lindenmuth

Sum of Angles in a Triangle by Terry Lee Lindenmuth
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2016-06-17 00:41
TriangleAngleGeometric Construction
In collections Geom. & Alg. Quadrilateral & Polygons Geometry Angle Investigations
This example demonstrates the property of the sum of angles in a triangle. Key mathematical concepts include the theorem of the sum of angles in a triangle. Using GeoGebra commands such as Polygon, Angle, Rotate, and Line, the example dynamically shows that the sum of the angles in a triangle is always 180 degrees. Suitable for middle school and above students to learn geometric construction and triangle properties.

GeoGebra Commands & Parameters

  1. Polygon(A, B, C) → poly1, c, a, b
  2. Angle(C, A, B) → α
  3. Angle(A, B, C) → β
  4. Angle(B, C, A) → γ
  5. Rotate(D, (-α), E) → D'
  6. Angle(D', E, D) → δ
  7. Rotate(D', (-β), E) → D''
  8. Angle(D'', E, D') → ε
  9. Rotate(D'', (-γ), E) → D'''
  10. Angle(D''', E, D'') → ζ
  11. Line(D, D''') → d
  12. Angle(D''', E, D) → η
  13. Textfield(Guess) → InputBox1