Perimeter of a triangle

Given a triangle with side lengths $a$, $b$, and $c$, its perimeter $P$ is $P = a + b + c$. The perimeter is a linear measure and is always a positive real number.

Important properties

• The perimeter depends only on the lengths of the sides.

• If the triangle is equilateral (all sides equal), the perimeter is $3a$ where $a$ is the side length.

• If the triangle is isosceles (two sides equal), the perimeter is $2a + b$ where $a$ is the length of the equal sides and $b$ is the base.

• The triangle inequality: For any triangle, the sum of the lengths of any two sides must be greater than the length of the third side.