Lesson Plan: Ambiguous Case of the Law of Sines Mathematics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to use the rule of sines to solve SSA (side-side-angle) ambiguous triangles.


Students will be able to

  • recognize when the use of the law of sines, to find an unknown length, can give rise to an ambiguous answer due to the possibility of two possible solutions (namely, when you are given two side lengths and a nonincluded, acute angle),
  • recognize that the use of a calculator will default to the acute version of the ambiguous triangle case,
  • solve an ambiguous triangle using the law of sines.


Students should already be familiar with

  • the law of sines.


Students will not cover

  • the law of cosines.

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