1 #include <iostream>
2 #include <cmath>
3 #include <iomanip>
4 using namespace std;
5 #define PI 3.141592653589793
6
7 struct node
8 {
9 double x;
10 double y;
11 };
12
13 node p_1;
14 node p_2;
15 node p_3;
16
17 double a;
18 double b;
19 double c;
20 double give_len(node a,node b);
21
22 int main()
23 {
24 //freopen("acm.acm","r",stdin);
25 double cos_c;
26 double sin_c;
27 double s;
28 while(cin>>p_1.x>>p_1.y>>p_2.x>>p_2.y>>p_3.x>>p_3.y)
29 {
30 a = give_len(p_1,p_2);
31 b = give_len(p_1,p_3);
32 c = give_len(p_2,p_3);
33 // cout<<"--- a"<<a<<endl;
34 // cout<<b<<endl;
35 // cout<<c<<endl;
36 cos_c = (a*a + b*b - c*c)/(2.0*a*b);
37 sin_c = sqrt((1 - cos_c*cos_c));
38 s = 0.5 * a*b*sin_c;
39 cout<<setiosflags(ios::fixed)<<setprecision(2)<<a*b*c*PI/(s*2.0)<<endl;
40 }
41 }
42
43 double give_len(node a,node b)
44 {
45 return sqrt( (a.x-b.x)*(a.x-b.x) + (a.y - b.y)*(a.y - b.y) );
46 }
