Triangles can be classified by various properties relating to their angles and sides. The most common classifications are described on this page.

This Page:
 Practice Identifying Triangle Types

Related Page:
 Online Triangle Calculator
 Triangle and its properties
Classifications of Triangles
Right Triangles
A right triangle has one 90° and a variety of oftenstudied properties including:
Equilateral triangle
The Equilateral triangle shown on the left has three equal sides and three equal 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°.
Practice Problems
Since this triangle has two congruent angles and two congruent sides, it is an Isosceles Triangle