Triangle is one of the basic shapes of geometry and is formed by connecting three points not in a straight line but by straight line segments. It is a geometric figure having three angles and three sides. A triangle is also a closed figure with three sides. A triangle with vertices

*A*,

*B*, and

*C* is denoted

*ABC.*
There are seven types of triangles depending upon their shapes and the degree of their angles. Triangles have some distinctive properties which are common to all types. The two most common properties are:

The interior angles of a triangle always add up to 180°

The exterior angles of a triangle always add up to 360°

The area and the perimeter of a triangle can be calculated by using the following geometric formula:

Area of a triangle = ½ × Base × Height

Perimeter of a triangle = Sum of three sides