Octagon: Polygon with eight sides

All sides of a regular octagon are the same length. Each corner is 135°. All corners added together equal 1080°.

Area

The amount of space a regular octagon takes up is

${\displaystyle {\text{Area}}=2(1+{\sqrt {2}})a^{2}.}$ 

a is the length of one of its sides.

Another way to write it is

${\displaystyle {\text{Area}}=2a^{2}({\sqrt {2}}+1).}$ 

•  
  This shape is called an octagram. It has one regular octagon in the middle.
•  
  The octagonal prism has 2 octagons in it: one on the top, and the other on the bottom.
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  A non-regular octagon
•  
  Making an octagon by folding paper

• Different types of polygons
• Hexagon
• Pentagon
• Square or quadrilateral
• Triangle