Perimeter of Plane Figures

What is Perimeter?

The perimeter of any closed plane figure is the distance covered along its boundary when you go around it once. For a polygon (a closed figure made of line segments), the perimeter is simply the sum of the lengths of all its sides.

Perimeter of a Rectangle

Consider a rectangle $ABCD$ with length $l$ and breadth $b$. Since opposite sides of a rectangle are equal:

• $AB = CD = \text{length} (l)$
• $BC = DA = \text{breadth} (b)$

Perimeter of a Square

A square is a special type of rectangle where all four sides are equal in length. If the length of a side is $s$:

Perimeter of a Triangle

For a triangle with sides of lengths $a$, $b$, and $c$:

If the triangle is equilateral (all sides equal), the perimeter is $3 \times \text{side}$.