Education Technology

Geometry: Triangle Inequality Theorem

by Texas Instruments


  • Students will identify the conditions necessary to build triangles given the lengths of 3 segments.
  • Students will use the Triangle Inequality Theorem to determine whether a triangle can be formed when given 3 segments.


  • triangle
  • inequality
  • segment
  • conjecture

About the Lesson

This lesson involves building triangles from three segments. As a result students will:

  • Manipulate given segments and make conjectures about the relationships between the lengths of the segments and the possibility of forming a triangle.
  • Use randomly generated side measures and manipulate the corresponding segments to determine whether the combination of measures will form a triangle.
  • Make and justify a conjecture describing the conditions that must be met to build triangles given segments of different length.