Education Technology

Nested Similar Triangles

Activity Overview

Discover the conditions that make triangles similar by moving the sides opposite the common angle in nested triangles.


  • Students will be able to identify the conditions that determine when nested triangles that share a common angle are similar triangles.
  • Students will validate conditional statements about nested triangles that share a common angle.


  • similar polygons
  • corresponding parts
  • parallel
  • nested triangles

About the Lesson

In this lesson, nested triangles have been created so that they share a common vertex and vertex angle. The students will drag the endpoints of the side that is opposite the common angle to discover the conditions that make the nested triangles similar. When students make congruent angle marks appear, the triangles will be similar.