Compute area, perimeter, apothem and interior angle of a regular pentagon.
A regular pentagon has 5 equal sides. Each interior angle is 108°. The apothem is the distance from the center to the midpoint of a side.
Area
A = ½ × perimeter × apothem
Apothem
a = s / (2 × tan(π/n))
Each interior angle is exactly 108°.
The apothem is the perpendicular distance from the center to any side. It is used to calculate area.