# Lesson Plan: Triangle Similarity Criteria and Their Applications Mathematics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to use the properties of similar triangles to solve problems.

#### Objectives

Students will be able to

• determine similarity using the angle–angle (AA) criterion; that is, if two corresponding angles have equal measures, the triangles are similar,
• determine similarity using the side-side-side (SSS) criterion; that is, if corresponding sides are in proportion, the triangles are similar,
• determine similarity using the side-angle-side (SAS) criterion; that is, if two corresponding sides are in proportion and the included angles have equal measure, the triangles are similar,
• use similarity to calculate unknown angle measures, scale factors, unknown lengths, and perimeters,
• use the similarity of two triangles to form and solve linear equations,
• use the similarity of two triangles to find indirect measurements in real-life situations.

#### Prerequisites

Students should already be familiar with

• parallel lines and equivalent angles,
• working with proportions,
• solving linear equations.

#### Exclusions

Students will not cover

• similarity of polygons,
• similarity problems including area and volume.