Education Technology

Investigating Segments in a Triangle

Activity Overview

In this activity, students investigate the midsegments of a triangle as in the previous activity. They continue to explore these segments and extend their understanding of the relationships that exist between the slopes of lines containing the segments. 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
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 30-31 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
    • Draw a segment to join the midpoints
    • Explore the relationships between the segment and the third side of the triangle - their lengths and the slopes of the lines containing the segments
    • The segment joining the midpoints of two sides of a triangle is parallel to the third side and has measure equal to one-half the measure of the third side
    • Test these conjectures using different sides of the triangle

    After the Activity

    Review student results:

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