Education Technology

Dynamic Geometry: Basic Constructions

Published on 06/09/2008

Activity Overview

Students use the Cabri™ Jr. application to draw triangles and construct perpendicular bisectors on the sides of a triangles. They study the properties of a triangle and understand how the measures of angles of a triangle is always 180 degrees.

Before the Activity

Install the Cabri: Jr. App on the students' graphing calculators using one of these two methods:

  • TI-Connect™,  a TI Connectivity Cable, and the Unit-to-Unit Link Cable
  • TI-Navigator™  "send to class" feature
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 1 - 19 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to the class.

    Follow the Activity procedures:

  • Construct an acute scalene triangle and label its vertices
  • Measure the angles of the triangle
  • Construct three perpendicular bisectors on each of the sides of the triangle
  • Determine the point of intersection of the perpendicular bisectors
  • Hide the perpendicular bisectors and display only the intersection point
  • Make conjectures about the intersection of the perpendicular bisectors of a triangle when the triangle is acute, right, or obtuse
  • Calculate the sum of measures of the angles of the triangle
  • Move a vertex and observe the change in the measure of the angles
  • After the Activity

    Review student results:

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