Tetracontagon

A tetracontagon or 40-gon is a shape with 40 sides and 40 corners.

 Regular tetracontagon 
All sides of a regular tetracontagon are the same length. Each corner is 171°. All corners added together equal 6840°.

 Area 
The amount of space a regular tetracontagon takes up is

a is the length of one of its sides.

When calculating polygonal numbers (numbers that can be represented as a regular polygon), 
 typically stands for a Triangular Number [1.4.9]. 
The formula to find the 
 40-gonal number (
) is often expressed using the 
 and 
 triangular numbers:

In this context, 
 is the 
 triangular number, calculated as 
 [1.3.7, 1.4.9]. 

40