计算几何题，使用的数学公式参考http://topic.csdn.net/t/20050329/22/3892541.html
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#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
const double PI = 3.141592653589793;
double Distance(double x1,double y1,double x2,double y2)
{//两点间的距离
double deltaX = x1-x2;
double deltaY = y1-y2;
return sqrt(deltaX*deltaX+deltaY*deltaY);
}
double CaculateCircum(double x1,double y1,double x2,double y2,double x3,double y3)
{//计算三角形外接圆周长
//海伦公式计算三角形面积
double a,b,c,L,S;
a = Distance(x1,y1,x2,y2);
b = Distance(x2,y2,x3,y3);
c = Distance(x1,y1,x3,y3);
L = (a+b+c)/2;
S = sqrt(L*(L-a)*(L-b)*(L-c));
//计算三角形外接圆周长
return PI*a*b*c/(2*S);
}
int main(void)
{
double x1,y1,x2,y2,x3,y3,circum;
while(cin>>x1>>y1>>x2>>y2>>x3>>y3)
{
circum = CaculateCircum(x1,y1,x2,y2,x3,y3);
cout<<fixed<<setprecision(2)<<circum<<endl;
}
return 0;
}
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本文转自Phinecos(洞庭散人)博客园博客，原文链接：http://www.cnblogs.com/phinecos/archive/2008/10/31/1323492.html，如需转载请自行联系原作者
