# integers.info

## Icosagon

### A polygon with 20 sides

 Interior Angle = 162° Central Angle = 18° Slice Area ≈ 0.155 r2 Total Area ≈ 3.09 r2 Circumference ≈ 6.257 r

### About Icosagons

An icosagon is a polygon with 20 sides, and the sum of its interior angles is 3240 degrees.

### 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
4Quadrilateral
5Pentagon
6Hexagon
7Heptagon
8Octagon
9Nonagon
10Decagon
11Hendecagon
12Dodecagon
13Tridecagon
14Tetradecagon
15Pentadecagon
16Hexadecagon
17Heptadecagon
18Octadecagon
19Enneadecagon
20Icosagon