### Classifications of Triangles

#### Right Triangles

A right triangle has one 90° angle and a variety of often-studied topics:

#### Equilateral triangle

The Equilateral triangleshown on the left has three congruent sides and three congruent angles.

Each angle is 60°.

#### Isosceles triangle

The Isosceles triangle shown on the left has **two** equal sides and two equal angles.

#### Scalene Triangle

The Scalene Triangle has no congruent sides. In other words, each side must have a different length.

#### Acute Triangle

The Acute Triangle has three acute angles (an acute angle measures less than 90°).

#### Obtuse Triangle

The Obtuse Triangle has an obtuse angle (an obtuse angle has more than 90°). In the picture on the left, the shaded angle is the obtuse angle that distinguishes this triangle.

Since the total degrees in any triangle is 180°, an obtuse triangle can only have one angle that measures more than 90°.