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Types of Triangles

Isosceles, Equilateral, Scalene, Obtuse. . .

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

Classifications of Triangles
Right Triangles
 
A right triangle has one 90° and a variety of often-studied properties including:


picture of equilateral triangle

The Equilateral triangle shown on the left has three equal sides and three equal angles.

Each angle is 60°




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

 

 



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


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


Obtuse Triangle
TheObtuse 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


What kind of triangle is pictured on the left?
Triangle Type



What kind of triangle is pictured on the left?

Triangle Type


What type of triangle is pictured on the left?
Answer


Obtuse Classify the triangle on the left
Answer


Obtuse Classify the triangle on the left
Answer