Classifications of Triangles
Right Triangles
![Right Triangle](images/right-triangles/right-triangle.jpg)
A right triangle has one 90° angle and a variety of often-studied topics:
Equilateral triangle
![Equilateral Triangle picture of equilateral triangle](/geometry/triangles/images/equilateral-triangles/equilateral-triangle.png)
The Equilateral triangleshown on the left has three congruent sides and three congruent angles.
Each angle is 60°.
Isosceles triangle
![Isosceles Triangle](/geometry/congruent_triangles/images/isosceles/isosceles-triangle-picture.gif)
The Isosceles triangle shown on the left has two equal sides and two equal angles.
Scalene Triangle
![Scalene Triangle](images/scalene.jpg)
The Scalene Triangle has no congruent sides. In other words, each side must have a different length.
Acute Triangle
![Acute Triangle](images/acute-triangles/acute.jpg)
The Acute Triangle has three acute angles (an acute angle measures less than 90°).
Obtuse Triangle
![Obtuse Triangle Obtuse Triangle](images/obtuse-triangles/obtuse-triangle-picture.gif)
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°.