What is the area of a regular 15-gon with a radius of 5mm

(assuming the radius is the inradius (or the apothem))
To get the side length,we use this formula:
side length = apothem * (2 * tan (180/15))
side length = 5 * 2 * 0.21256
side length = 2.1256

Polygon Area = (# of sides * side length * apothem) / 2
Polygon Area = (15 * 2.1256 * 5) / 2
Polygon Area = 79.71