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Triangles — Part 2: Criteria for similarity and applications

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Lesson

Triangles, Part 2: Criteria for similarity and real-world heights

Three quick tests for similar triangles — and how a shadow can measure a monument.

In this lesson you will

  • State the AA, SSS and SAS similarity criteria and match vertices correctly
  • Choose the right criterion for a given figure
  • Prove two triangles similar with a reason for every step
  • Find unknown sides and solve height-and-shadow problems using similarity
Vertical objects + parallel sun rays ⇒ equal angles ⇒ similar triangles (AA).