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


More Information

Indicator marks for sides and angles in a triangle diagram.

Relationship between sides and angles.

Demonstration Applet

Perimeter of a Triangle
Perimeter of a Triangle

Area of a Triangle

b: The length of a base (side) of a triangle

a: The length of the altitude of the triangle (corresponding to the chosen base)

A: The area of the interior of the triangle (Explanation of formula).

Demonstration Applet (Area of the Interior of a Triangle)