Education Technology

Angles of a Triangle

Activity Overview

In this activity, students will measure angles and investigate the relationships between interior and exterior angles of a triangle. They understand the definition of interior angles, exterior angles, adjacent angles, supplementary angles, and remote interior angles.

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 cables
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 45 - 52 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to your class.

    Follow the Activity procedures:

  • Draw a triangle to fill most of the screen
  • Measure the three interior angles
  • Calculate the sum of the interior angles
  • Drag a vertex of an angle and observe what happens to the angle measures and their sum
  • Construct a line on one side of the triangle
  • Construct and label a point on the line to the right of the triangle
  • Measure the exterior angle, adjacent interior angle, and the two remote interior angles
  • Understand the relationship between exterior angles and the interior angles
  • After the Activity

    Students will fill in the Data Collection and Analysis sheet.

    Review student results:

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