# Lesson Plan: Triangle inequality Mathematics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to define the triangle inequality and identify whether the given side lengths are valid for constructing a triangle.

#### Objectives

Students will be able to

- understand and use the triangle inequality that states that the sum of the lengths of any two sides in a triangle is greater than the length of the third side,
- identify whether the given side lengths are valid for constructing a triangle,
- complete geometric proofs using the triangle inequality.

#### Prerequisites

Students should already be familiar with

- forming inequalities for measures of angles relative to one another in a triangle,
- forming inequalities for lengths of sides relative to one another in a triangle,
- the sum of angles in a triangle,
- isosceles triangles.

#### Exclusions

Students will not cover

- similarity of triangles.