Unit 6 · Similarity and Dilations

6.7Triangle Proportionality Theorem

Quick Answer

Extensions of the Triangle Proportionality Theorem: the Angle Bisector Theorem states that an angle bisector divides the opposite side in the ratio of the adjacent sides.

Essential Question

How does the Angle Bisector Theorem extend proportional reasoning from parallel lines to angle bisectors within a triangle?

Learning Goals

  • 1State the Angle Bisector Theorem.
  • 2Apply the Angle Bisector Theorem to find missing lengths.
  • 3Apply the Three Parallel Lines Theorem.
  • 4Solve multi-step proportionality problems.

Key Vocabulary

Angle Bisector Theorem

An angle bisector of a triangle divides the opposite side into segments proportional to the adjacent sides.

Three Parallel Lines Theorem

Three parallel lines cut two transversals into proportional segments.

Full lesson content coming soon

Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.