Lines Parallel to a Side of a Triangle

This Lines Parallel to a Side of a Triangle lesson plan also includes:

Your geometry learners will thoroughly explore the Side-Splitting Theorem and how a line, parallel to one of the sides of a triangle, splits the other two sides proportionally. They then collaborate to complete three exploratory tasks involving geometric construction, Geometers Sketch Pad, and distance formula on a graph in the coordinate plane, to write a conjecture and test it. Finally the learners do a formal proof of the Side-Splitting Theorem and solve triangles with their new knowledge.

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CCSS: Designed
Additional Tags


  • Well organized lesson plan that includes many math practice standards as well as a geometry standard

  • None
Common Core