Area  Perimeter 
where n is the number of sides 

Use the Polar Moment of Inertia Equation for a triangle about the (x_{1}, y_{1}) axes where: Multiply this moment of inertia by n. This is the Polar Moment of Inertia of a Regular n sided Polygon about the Centroidal Axis. 

Moment of Inertia 
Geometric Properties 