Lesson Plan

Informal Proof of AA Criterion for Similarity

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What does it take to show two triangles are similar? The 11th segment in a series of 16 introduces the AA Criterion for Similarity. A discussion provides an informal proof of the theorem. Exercises and problems require scholars to apply the theorem to justify whether two given triangles are similar.

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CCSS: Designed
Additional Tags
Instructional Ideas
  • Incorporate using geometry software to get more precise measurements
  • Have individuals determine the transformations that would show their two drawn triangles are similar
Classroom Considerations
  • Class members should be comfortable with the Fundamental Theorem of Similarity
Pros
  • Some problems require more than AA to prove the similarity, they also require the Triangle Sum Theorem
  • The answer key provides sample justifications
Cons
  • None
Common Core