Lesson Plan: Law of Cosines Mathematics • 11th Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to find the sides and angles in non-right triangles using the law of cosines.

Objectives

Students will be able to

  • recall the law of cosines, 𝑎=𝑏+𝑐2𝑏𝑐𝐴cos,
  • recognize how the law of cosines can be applied to a triangle to determine an unknown side length (given a diagram or otherwise),
  • recognize how the law of cosines can be applied to a triangle to determine an unknown angle measure (given a diagram or otherwise).

Prerequisites

Students should already be familiar with

  • right triangle trigonometry.

Exclusions

Students will not cover

  • the law of sines,
  • real-world applications of the law of cosines.

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