Volume of a Bipyramid (Regular base n-sided Polygon) Formula

Equation for calculate volume of a bipyramid (regular base n-sided polygon) is,

$V=\frac{\frac{n}{6}·h·l^2}{\tan \left(\frac{\pi }{n}\right)}$

where,
V = The volume of the bipyramid
n = Number of the sides of the base
h = The height from the base to the apex
l = The length of the side of the base
π = pi (3.141592653589793)