regular pentagram

[mathe25]

ii have a regular pentagram and i must find S (surface area)of the stained area...i only have r=1...!!!

 

[galactus]

See here:

http://www.mathalino.com/reviewer/plane-geometry/area-of-regular-five-pointed-star

 

[mathe25]

See here:

can someone hel me to prove the formulat for central and iscribed angle ???