###### Exercise56

The formula

\(\displaystyle{A=\frac{1}{2}\,r\,n\,s}\)

gives the area of a regular polygon with side length \(s\text{,}\) number of sides \(n\) and, apothem \(r\text{.}\) (The *apothem* is the distance from the center of the polygon to one of its sides.)

What is the area of a regular \(40\)-gon with \(s= {84\ {\rm in}}\) and \(r={66\ {\rm in}}\text{?}\)

The area is .