Education Technology

Reflecting a Triangle in the Coordinate Plane

Published on 06/09/2008

Activity Overview

In this activity, students use the drawing and measurement tools of Cabri™ Jr. to blend coordinate geometry with drawing tools. They visualize symmetry and reflect a point across the y-axis. NCTM Geometry Standards: Specify locations and describe spatial relationships using coordinate geometry and other representational systems. Apply transformations and use symmetry to analyze mathematical situations.

Before the Activity

  • Install the Cabri Jr. App on the students' graphing calculators using TI Connect™, a TI Connectivity Cable, and the Unit-to-Unit Link Cable
  • Set up the TI-Navigator™ system
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 46 - 47 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to your class.

    Follow the Activity procedures:

  • Draw a triangle
  • Find the coordinates of the triangle
  • Reflect the triangle across the y-axis
  • Find the coordinates of the reflected triangle
  • Explore the relationship between the original coordinates and the coordinates of the reflected triangle


  • TI-Navigator activity:
  • Load a background image of a triangle in Quadrant 1
  • Have students mark a point on the triangle then mark a second point which is the image of the first point reflected across the y-axis
  • After the Activity

    Review student results:

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary