Show more than one way to prove similarity. Scholars learn three different methods to show two triangles are similar, Angle-Angle, Side-Side-Side, and Side-Angle-Side. Pupils practice applying these methods to determine whether two given triangles are similar, and then apply the methods to determine missing sides in triangles.

Concepts

geometric proofs, proofs, two-column proofs, similar triangles, similarity

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Instructional Ideas

• Provide opportunities for the class to write two-column proofs showing two triangles are similar

Classroom Considerations

• Second lesson in a four-part unit
• Assumes individuals are comfortable working with proportions

• This video is hosted on YouTube

Pros

• The answer sheet shows any work required to arrive at the solution
• Contains application problems that require the lesson's skills

Cons

• None

Common Core

SL.9-10.2 SL.11-12.2 MP3 MP6 HSG-SRT.A.3 HSG-SRT.B.5