7 3
6 8
3 8
1 7
0 3
4 0
6 1
9 6

If you draw this polygon on paper, you understand yours mistake ;)

Edited by author 06.03.2009 21:05

By the way the correct answer is 0.38528021

I have WA 12 too. I understood why my solution is wrong. So, what the idea of right solution?