Regular Five Pointed Star

By “side” the author meant the distance $AB$ from vertex to a distant vertex.

The radius of the circle the star is inscribed in can be obtained from triangle $CBO$ and is $r=\dfrac {8}{\cos18^\circ}$

Area of triangle $OBD$ can be obtained from $r$ and the angles inside the triangle, which are $18^\circ$ and $36^\circ$ next to $r$ , and $126^\circ$ oppsite.

$[OBD]= \dfrac{r^2\sin18^\circ\sin36^\circ}{2\sin126^\circ}$

Area of the star is made of $10$ such triangles and is

$A=\boxed{79.43}$