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Construct 120° Angle with Compass

Construct 120° Angle with Compass
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2017-11-28 20:58
AngleVectorGeometric Construction
In collections Mathematics Form 1
This example demonstrates how to construct a 120° angle using a compass. Key mathematical concepts include angles and geometric construction. Using GeoGebra commands such as Segment, Circle, Vector, and Translate, the angle can be constructed accurately. Suitable for middle school and above students to learn geometric construction techniques.

GeoGebra Commands & Parameters

  1. Segment(O, A) → f
  2. Point(f) → P
  3. Circle(O, P) → e
  4. If(a ≟ true, Rotate[A, 120°, O], Rotate[A, -120°, O]) → B'
  5. Circle(P, O) → h
  6. If(a ≟ true, Rotate[O, -40°, P], Rotate[O, 40°, P]) → C
  7. If(a ≟ true, Rotate[O, (-β), P], Rotate[O, β, P]) → E
  8. If(a ≟ true, Arc[h, E, C], Arc[h, C, E]) → k
  9. If(a ≟ true, Rotate[P, α, O], Rotate[P, (-α), O]) → D
  10. If(a ≟ true, Arc[e, P, D], Arc[e, D, P]) → c
  11. Vector(O, B') → u
  12. Translate(O, Vector[(b * u)]) → O'
  13. Segment(O, O') → g
  14. If(a ≟ true, Angle[A, O, B'], Angle[B', O, A]) → γ
  15. If(a ≟ true, Rotate[P, 150°, O], Rotate[P, -150°, O]) → P'
  16. If(a ≟ true, Intersect[k, c, 1], Intersect[k, c, 2]) → Q
  17. Circle(Q, O) → d
  18. If(a ≟ true, Rotate[O, -40°, Q], Rotate[O, 40°, Q]) → F
  19. If(a ≟ true, Rotate[O, (-δ), Q], Rotate[O, δ, Q]) → G
  20. If(a ≟ true, Arc[d, G, F], Arc[d, F, G]) → p
  21. SelectedIndex(Bahasa) → nn
  22. If(nn ≟ 1, "Animate", "Animasi") → Tex1
  23. If(nn ≟ 1, "Stop", "Berhenti") → Tex2
  24. If(nn ≟ 1, "Resume", "Teruskan") → Tex3
  25. If(nn ≟ 1, "To construct an angle of 120° at O using a pair of compasses", "Membina sudut 120° pada O dengan menggunakan jangka lukis") → text3
  26. If(nn ≟ 1, "Center O Radius OP", "Pusat O Jejari OP") → text1
  27. If(nn ≟ 1, "Center P Radius OP", "Pusat P Jejari OP") → text2
  28. If(nn ≟ 1, "Center Q Radius OP", "Pusat Q Jejari OP") → text4