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Broken Protractor

Broken Protractor
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2018-01-24 01:27
AngleGeometric ConstructionSlider Animation
In collections Lines and Angles
This example demonstrates how a broken protractor can be used to measure angles. Key mathematical concepts include angle measurement and geometric construction. It utilizes commands such as RandomElement, Sequence, Arc, Segment, Point, If, Vector, Angle, and Text in GeoGebra. Suitable for middle school and above students to learn angle measurement and geometric construction.

GeoGebra Commands & Parameters

  1. RandomElement({"L", "R"}) → zeroOn
  2. Sequence(Segment[((0.93 * cos(i°)), (0.93 * sin(i°))), (cos(i°), sin(i°))], i, 5, 175, 5) → fives
  3. Sequence(Segment[((0.96 * cos(i°)), (0.96 * sin(i°))), (cos(i°), sin(i°))], i, 1, 179, 1) → ones
  4. Arc(x^(2) + y^(2) = 1, (1, 0), (-1, 0)) → c
  5. Sequence(Segment[((0.9 * cos(i°)), (0.9 * sin(i°))), (cos(i°), sin(i°))], i, 0, 180, 10) → tens
  6. Segment(A, B) → f
  7. Segment(C, D) → g
  8. Point(c) → E
  9. Segment(E, F) → h
  10. Segment(F, G) → i
  11. Point(c) → H
  12. Segment(G, H) → j
  13. Sequence(Text[If[zeroOn ≟ "R", i, 180 - i] + "°", Point[{(0.813 * cos(i°)) - (0.04 * abs(cos(i°) - (0.28 * (i ≟ 90)))), (0.813 * sin(i°)) - (0.02 * abs(cos(i°)))}]], i, 0, 180, 10) → L_1
  14. If(zeroOn ≟ "R", angleMeasure, 180° - angleMeasure) → shownAngleMeasure
  15. Vector(((1.15 * cos(shownAngleMeasure)), (1.15 * sin(shownAngleMeasure))), (cos(shownAngleMeasure), sin(shownAngleMeasure))) → v
  16. If(zeroOn ≟ "L", (-1, 0), (1, 0)) → zeroPoint
  17. Vector((0, 0), zeroPoint) → ray1
  18. Vector((0, 0), (cos(shownAngleMeasure), sin(shownAngleMeasure))) → ray2
  19. Angle(ray1, ray2) → α
  20. Text(angleMeasure, ((0.5 * cos(textAngle)), (1 / 3 * sin(textAngle)))) → angleText