Unit 6 · Similarity and Dilations

6.4AA Triangle Similarity

Quick Answer

AA Similarity: if two angles of one triangle are congruent to two angles of another triangle, the triangles are similar. Since angle sums are 180°, two angle pairs are sufficient.

Essential Question

Why is knowing just two pairs of congruent angles enough to guarantee that two triangles are similar?

Learning Goals

  • 1State the AA Similarity Postulate.
  • 2Identify AA similarity in diagrams.
  • 3Write similarity statements for AA-similar triangles.
  • 4Use AA similarity to find missing side lengths.

Key Vocabulary

AA Similarity Postulate

If two angles of one triangle are congruent to two angles of another, the triangles are similar.

Angle-Angle (AA)

The shortcut for proving triangle similarity using two pairs of congruent angles.

Full lesson content coming soon

Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.