Proving Triangle Similarity

10th Gradeβ€’45 minutes

Learning Objective

I can prove that two triangles are similar using the AA, SAS, and SSS similarity theorems.

Key Concepts

Side-Side-Side (SSS) similarity states that two triangles are similar if the lengths of their corresponding sides are proportional.

Side-Angle-Side (SAS) similarity states that two triangles are similar if they have two pairs of corresponding sides that are proportional and the included angles are congruent.

Angle-Angle (AA) similarity states that two triangles are similar if they have two pairs of corresponding angles that are congruent.

Practice Questions

This lesson includes 9 practice questions to reinforce learning.

View questions preview

1. State the Side-Side-Side (SSS) Similarity Theorem in your own words.

2. If triangle PQR has sides PQ = 5, QR = 7, RP = 9 and triangle XYZ has sides XY = 10, YZ = 14, and ZX = 18, are the triangles similar? Explain why or why not.

3. State the Side-Angle-Side (SAS) Similarity Theorem in your own words.

...and 6 more questions

Educational Video

Triangle Similarity - SSS, SAS, and AA 128-2.28

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