Perimeter

Perimeter

A perimeter is a path that surrounds a two-dimensional shape. The term may be used either for the path or its length—it can be thought of as the length of the outline of a shape. The perimeter of a circle or ellipse is called its circumference.

Calculating the perimeter has several practical applications. A calculated perimeter is the length of fence required to surround a yard or garden. The perimeter of a wheel (its circumference) describes how far it will roll in one revolution. Similarly, the amount of string wound around a spool is related to the spool's perimeter.

Formulas

shape	formula	variables
circle		where  is the radius of the circle and  is the diameter.
regular polygon		where  is the number of sides and  is the distance between center of the polygon and one of the vertices of the polygon.
equilateral polygon		where  is the number of sides and is the length of one of the sides.
rectangle		where is the length and is the width.
triangle		where , and are the lengths of the sides of the triangle.
square/rhombus		where is the side length.
general polygon		where is the length of the -th (1st, 2nd, 3rd ... nth) side of an n-sided polygon.

cardoid  
(drawing with )
 
 
 

The perimeter is the distance around a shape.

Video: What is a Perimeter in Math?

Polygons

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