
# 2.B: Other Triangle Properties


## Overview

The purpose of this lesson is to identify and use other triangle properties.

This lesson will address the following CCRS Standard(s) for Geometry:

• 8.G.5: Use informal arguments to establish facts about the angle sum and exterior angles of triangles, above the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so

## Directions

1. Take notes while watching videos below
2. Go to http://wamap.org and log into our course to complete assignment 2.B with 80% or better.

### Watch

Other Triangle Properties [11:14]

### Do

Complete assignment 2.B with 80% or better at http://wamap.org

## Summary

In this lesson we have learned:

• Isosceles triangles have two congruent sides and two congruent angles
• The sum of the angles of a triangle is 1800
• The exterior angle of a triangle is equal to the sum of the opposite two angles
• When combined, the two shortest sides of a triangle are longer than the third (longest) side