Concept

Triangle

A triangle is a polygon with three angles and three sides. The symbol

△

is used to algebraically denote a triangle. Next to this symbol, the three vertices of the triangle are written in any order. For example,

△ A B C

and

△ B C A

both denote the triangle whose vertices are

A,

B,

and

C .

Triangles can be classified either according to their side lengths or to their internal angle measures.

The following table lists all the different types of triangles according to their corresponding classification.

Classification of Triangles
By Angle Measures	By Side Lengths
Acute Triangle	Scalene Triangle
Right Triangle	Isosceles Triangle
Obtuse Triangle	Equilateral Triangle
Equiangular Triangle	Equilateral Triangle

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