math

http://mathcentral.uregina.ca/qq/database/qq.09.06/s/chetna2.html

You separate the star into 5 triangles and a pentagon.

No need to separate I got it.

Area of a star(regular) of side length a

= \(\left(\dfrac{5\sqrt{10-2\sqrt5}}{8}+\dfrac{(3-\sqrt5)(\sqrt{10+2\sqrt5}+2\sqrt{5+2\sqrt{5}})}{8} \right)\cdot a^2\)

Checked. No mistakes. Just substitute and use a calculator :D

Although it is really complicated......

Anyone know what I am doing XD