Education Technology

Geometry: Corresponding Parts of Similar Triangles
by Texas Instruments

Updated on August 21, 2019


  • Students will identify corresponding parts of similar triangles.
  • Students will use the ratio of similarity to find missing measures in similar triangles.
  • Students will relate the ratio of similarity to reductions and enlargements.


  • scale factor (ratio of similarity)
  • corresponding parts
  • reduction
  • enlargement
  • coincide; coincidental

About the Lesson

This lesson involves manipulating the scale factor (r) and observing changes in similar triangles; changing the ratio of similarity; and matching corresponding parts of similar triangles. As a result students will:

  • Produce reductions, enlargements, and congruent figures.
  • Compare corresponding angles and corresponding sides to be compared.
  • Infer the relationship between ratio of similarity (scale factor) and the measures of the sides.