Education Technology

Measuring Angles in a Triangle

Published on 06/09/2008

Activity Overview

In this activity, students learn about the sum of the angles in a triangle. They understand triangles and their interior angles. NCTM Geometry Standard covered: Analyze characteristics and properties of 2- and 3-dimensional geometric shapes and develop mathematical arguments about geometric relationships.

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 7-8 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to your class.

    Follow the Activity procedures:

  • Draw a triangle using the Apps
  • Label the vertices of the triangle
  • Measure the interior angles of the triangle
  • Find the sum of the angles of the triangle
  • Move the vertex and measure the angles of the triangle and find the sum of its interior angles


  • TI-Navigator activity:
  • Use Screen Capture to identify problems with labeling
  • After the Activity

    Review student results:

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