Education Technology

Investigating Lengths of Segments in a Triangle

Published on 06/09/2008

Activity Overview

In this activity, students connect the midpoints of two sides of a triangle, to draw the midsegment of the triangle. They investigate how the length of this segment relates to the third side of the 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 28-29 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 midpoints of two sides of the triangle
  • Draw and measure the segment joining the midpoints of these two sides
  • Compare the length of this segment to the length of the third side of the triangle


  • TI Navigator activity:
  • Use Screen Capture to observe and assess individual progress in drawing and exploring
  • After the Activity

    Review student results:

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