Constructing the Midpoint and Perpendicular Bisector of a Segment

Constructing the Midpoint and Perpendicular Bisector of a Segment
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2025-02-08 18:50
In collections Euclidean Geometry
This example demonstrates how to construct the midpoint of a given segment and then build its perpendicular bisector, illustrating the key fact that points on the perpendicular bisector are equidistant from the segment’s endpoints. The main math ideas include the definition of a midpoint, the properties of the perpendicular bisector (passes through the midpoint and forms a right angle with the segment), and using circle intersections to enforce equal distances. Construction workflow in GeoGebra: create points (Point / PointIn) for endpoints and intermediate points; represent the segment (Segment) and use Circle centered at each endpoint with the same radius; compute the intersections of the two circles (Intersect) to obtain two symmetric points; draw the perpendicular bisector as a line through those intersection points (Line); and use Distance (optionally Angle) to verify equal distances to both endpoints and the perpendicular relationship. The setup supports guided activities with and without GeoGebra and is suitable for middle/high school geometry and geometry-construction practice.

GeoGebra Commands & Parameters

  1. Point(xAxis) → PEEPST
  2. PointIn(peep) → A
  3. PointIn(peep) → B
  4. Segment(A, B) → segmAB
  5. Point(segmAB) → C_{1}
  6. Circle(A, Segment[A, B]) → cfrAB
  7. Circle(B, Segment[A, B]) → cfrBA
  8. Intersect(cfrAB, cfrBA, 2) → D
  9. Intersect(cfrAB, cfrBA, 1) → C
  10. Distance(A, B) → rag
  11. Line(C, D) → rCD
  12. Midpoint(A, B) → M
  13. Segment(A, M) → segmAM
  14. Segment(B, M) → segmMB
  15. Angle(B, M, C) → ang

AI Drawing Prompt Reference

Pick two points on the x-axis as endpoints and connect them to form a segment. Choose an arbitrary point on the segment. Draw two circles centered at each endpoint with radius equal to the segment length; they intersect at two points. Draw a line through these two intersection points, which is the perpendicular bisector of the segment. Then mark the midpoint of the segment, connect it to both endpoints, and show the angle between the midpoint and one intersection point to verify equal distances.
The prompt above was compiled from the original drawing commands and is for reference only.