# Table of Contents

# The Definition of a Triangle. Types of triangle. Construction of Triangles

# The sides of the triangle and their properties

Corollaries of the triangle inequality

The perimeter and semiperimeter of a triangle

# The angles of the triangle and their properties

The properties of angles of a triangle

The relationship between sides and angles in a triangle

If the angles of one triangle are equal to the angles of another triangle

# The exterior angle of a triangle

Definition of the exterior angle. The properties of the exterior angle

The relationship between the exterior angle and the interior angles of a triangle