# integers.info

## Quadrilateral or Tetragon

### A polygon with 4 sides

 Interior Angle = 90° Central Angle = 90° Slice Area = 0.5 r2 Total Area = 2 r2 Circumference ≈ 5.657 r

A quadrilateral is a polygon with 4 sides, and the sum of its interior angles is 360 degrees. A regular quadrilateral is also called a square.

### About Regular Polygons

The values in the table above assume a regular polygon as in the picture. In a regular polygon, all angles and sides are equal, which means that a perfect circle can be drawn across all the vertices. The radius of this circle is called the circumradius, and is denoted r in the calculations above.

The more sides the regular polygon has, the more similar to a circle it becomes. As a result, the circumference gets closer and closer to 2 × π × r (≈ 6.283 r), and the area gets closer and closer to π × r2 (≈ 3.1415 r2).

### List of Polygons

Here are all the polygons with twenty or less sides:

Number of SidesPolygon Name
3Triangle
5Pentagon
6Hexagon
7Heptagon
8Octagon
9Nonagon
10Decagon
11Hendecagon
12Dodecagon
13Tridecagon