Geometric Construction of Axial Symmetry: Mirror Image of Points and Figures

Geometric Construction of Axial Symmetry: Mirror Image of Points and Figures
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2023-03-22 20:30
In collections geometriadinamica.es
This example demonstrates how to construct and visualize axial symmetry in the plane, highlighting the corresponding positions of points and whole shapes on opposite sides of a symmetry axis. Key concepts include axial symmetry (reflection about a line), image (mirror) points, and geometric construction principles such as perpendicular lines and the perpendicular bisector (used to justify symmetry). The construction uses GeoGebra commands and objects: Line and Ray to form the reference and symmetry axis; Circle and CircleArc to build curved parts so the “whole figure” can be mirrored; Intersect to compute critical intersection points that define vertices and their images; OrthogonalLine and LineBisector to obtain perpendicular relations needed for determining symmetry; and Mirror to reflect the relevant points/objects across the axis. Point and text annotations help track correspondences. Suitable for middle and high school geometry lessons, especially topics on transformations and geometric construction.

GeoGebra Commands & Parameters

  1. Line(A, B) → b
  2. Circle(A, d1) → d
  3. Circle(B, d1) → e
  4. Intersect(d, b, 2) → C
  5. Intersect(e, b, 1) → D
  6. OrthogonalLine(A, b) → f
  7. OrthogonalLine(B, b) → g
  8. Point(f) → E
  9. OrthogonalLine(E, f) → h
  10. Intersect(g, h) → F
  11. Circle(E, d1) → k
  12. Circle(F, d1) → p
  13. Intersect(k, h, 1) → G
  14. LineBisector(E, F) → i
  15. Ray(A, D) → j
  16. Intersect(d, j) → I, N
  17. Intersect(e, j, 2) → J
  18. Ray(D, A) → l
  19. Intersect(e, l) → K, L
  20. OrthogonalLine(D, b) → m
  21. Intersect(b, i) → H
  22. Point(i) → M
  23. CircleArc(M, A, B) → q
  24. OrthogonalLine(C, b) → n
  25. Intersect(q, n, 1) → O
  26. Mirror(O, H) → O'

AI Drawing Prompt Reference

Draw an axial symmetric figure with points A and B, and line b as the symmetry axis. Use circles d and e centered at A and B, respectively, intersecting line b to get points C and D. Construct perpendicular lines f and g through A and B, intersecting at points E and F. Construct circles k and p centered at E and F, intersecting at points G and H. Construct the perpendicular bisector i of E and F, and rays j from A to D and from D to A, intersecting at points I and N, and J and K, respectively. Construct a perpendicular line m from D to line b, intersecting the perpendicular bisector i at point H. Construct an arc q with M as the center and A and B as endpoints, intersecting the perpendicular line n at point O, and mirror O to H to get O'.
The prompt above was compiled from the original drawing commands and is for reference only.