Polygon with five sides and five vertices.

The sum of the internal angles of a pentagon is $540\degree$.

The apothem of a regular pentagon is a line segment from the center/centre to the midpoint of one of its sides.

The area of a regular pentagon is given by the formula:

where $p$ is the perimeter and $a$ the apothem of the regular pentagon.

We can also calculate the area of a regular pentagon given its side $s$: