Education Technology

Inscribing a Circle in a Triangle

Activity Overview

In this activity, students bisect the angles of a triangle and find the incenter of the triangle. They find the distance from the incenter to the side of the triangle and use it as radius. With the incenter as the center, they inscribe a circle in a triangle. 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 23-24 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to your class.

    Follow the Activity procedures:

  • Send the figure saved as an APP VAR from Activity 8 to the students via TI-Navigator

  • Use the triangle
  • Draw the bisector of each angle of the triangle
  • Locate the incenter
  • Find the distance from the incenter to a side of the triangle
  • Inscribe a circle in the triangle
  • After the Activity

    Review student results:

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