Unit 3, Lesson 10# Informal Proof of AA Criterion for Similarity

EngageNY 45 min(s)

Students know an informal proof of the angle-angle (AA) criterion for similar triangles. Students present informal arguments as to whether or not triangles are similar based on the AA criterion. Recall the exercise we did using lined paper to verify experimentally the properties of the fundamental theorem of similarity (FTS). In that example, it was easy for us to see that that the triangles were similar because one was a dilation of the other by some scale factor.