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Parts of a Circle: Radius, Diameter, Chord, Arc and Sector

Parts of a Circle: Radius, Diameter, Chord, Arc and Sector
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2025-03-21 17:58
CircleAngleTrigonometryGeometric ConstructionSlider Animation
In collections Euclidean Geometry
This example uses interactive GeoGebra constructions to help learners explore and identify the main parts of a circle. It visually connects circle elements—center, radius, diameter, chord, arc, and sector (and optionally semicircle/annulus)—with their defining relationships. The core math concepts are the basic geometry of a circle: how radii determine diameter, how a chord is formed by intersecting a circle with a line segment, and how arcs and sectors are determined by points on the circle and the central angle. Construction highlights from the given GeoGebra command set include: Circle and Point for building the circle and defining points (e.g., disc/cerchio/circ, and the center O); Line/Segment combined with Intersect to create chords and compute intersection points; CircleArc for arcs (arcoAB/arcoBA); CircleSector for sectors (sect1/sect2); Radius for radii (radiA/radiB); AngularBisector and Tangent to demonstrate angle bisectors and tangent-related features; Semicircle and related objects for half-circle/diameter variants; and If, SelectedIndex, and PointIn to drive conditional display, selection logic, and region membership checks (e.g., inner/innerRad and annulus inner region). Suitable for middle school through high school geometry lessons, practice, and interactive classroom demonstration.

GeoGebra Commands & Parameters

  1. Circle(O, B_1) → given
  2. Point(given) → A
  3. Line(A, O) → a_1
  4. Intersect(given, a_1, 2) → D
  5. Point(given) → B
  6. Segment(O, A) → radiA
  7. Segment(A, D) → diam
  8. Segment(A, B) → chord
  9. CircleArc(O, A, B) → arcoAB
  10. CircleArc(O, B, A) → arcoBA
  11. CircleSector(O, A, B) → sect1
  12. CircleArc(O, A, B) → segm1
  13. CircleArc(O, B, A) → segm2
  14. Radius(given) → givenRad
  15. PointIn(feasibleAn) → A'
  16. Circle(O, A') → ann
  17. Semicircle(D, A) → semic
  18. Segment(D, A) → diamTratt
  19. CircleSector(O, A, D) → halfDisc
  20. CircleSector(O, B, A) → sect2
  21. SelectedIndex(ddMenuEn) → is
  22. SelectedIndex(ddMenuIt) → isIt
  23. Circle(O, A') → inner
  24. Radius(inner) → innerRad
  25. Segment(O, B) → radiB
  26. Angle(A, O, B) → ang1
  27. Angle(B, O, A) → ang2
  28. Segment(O, A) → radTratt1
  29. Segment(O, B) → radTratt2
  30. Point(given) → I
  31. Segment(B, I) → inscr2
  32. Segment(I, A) → inscr1
  33. Angle(B, I, A) → inscrAng
  34. If(arg(A) > 0°, arg(A), arg(A) + 360°) → ppA
  35. If(arg(B) > 0°, arg(B), arg(B) + 360°) → ppB
  36. If(arg(I) > 0°, arg(I), arg(I) + 360°) → ppI
  37. AngularBisector(B, I, A) → bisettr
  38. Intersect(Arc[given, A, B], bisettr) → IN,
  39. Segment(A, B) → segmAB
  40. Tangent(A, given) → tgA,
  41. Segment(A1, A2) → segmTg
  42. Angle(B, A, A1) → tempAng
  43. If(tempAng ≠ inscrAng, Angle[B, A, A2], Angle[B, A, A1]) → angCirc2

AI Drawing Prompt Reference

Draw a circle with key elements such as the center, radius, diameter, chord, arc, and sector. The center is the circle's center, the radius is the distance from the center to the circumference, and the diameter is the longest chord passing through the center. A chord is formed by a line intersecting the circle, while arcs and sectors are determined by points on the circle and central angles. The construction order: first draw the circle and center, then the radius and diameter, followed by the chord and arc, then the sector and semicircle, and finally add tangent lines and angle bisectors.
The prompt above was compiled from the original drawing commands and is for reference only.