• Czech: obvod
• Dutch: omtrek, perimeter
• Finnish: kehä
• Spanish: perímetro

• Dutch: omtrek, perimeter

The perimeter is the distance around a given two-dimensional object. The word perimeter is a Greek root meaning measure around, or literally "around measure".

Practical uses

Calculations of perimeter and area have considerable practical applications. Perimeter is used in calculating the border of an object such as a yard or flowerbed when a fence or other border is being installed around the edges. Area is used when all the area inside of a perimeter is being covered with something, such as a yard being covered with sod or fertilizer.

In military usage, the term perimeter defines a geographic area of importance, such as a physical installation or defensive work, but can also refer to a theoretical construct such as an all-round defense formed by a small group of soldiers, the purpose of which is mutual protection of each other rather than defence of actual territory.

Formulas

Polygons

As a general rule, the perimeter of a polygon can always be calculated by adding all the length of the sides together. So, the formula for triangles is P=a+b+c, where a, b and c stand for each side of it. For quadrilaterals the equation is P=a+b+c+d. For equilateral polygons, P=na, where n is the number of sides and a is the measure of the side.

Circles

For circles the equation is P = 2 \cdot \pi \cdot r

or P = d \cdot \pi

• P stands for the perimeter,
• r stands for the radius
• \pi is the mathematical constant pi (\pi=3.14159265...)
• d stands for the circle's diameter (twice the radius of a circle)

(The dot means multiply or times)

In General

If r is considered to be the distance from the centre of a regular polygon to one of its vertices (or in the case of a circle, the radius), the following holds true:

P = \frac

• P stands for the perimeter,
• r stands for the radius
• A stands for the area

See also

• Isoperimetric inequality
• Circumference
• Pythagorean Theorem
• Wetted perimeter

External links

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