OJ-Problems-Source/HDOJ/1374_autoAC.cpp

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2016-08-13 23:51:27 +08:00
#include <stdio.h>
#include <math.h>
#define PI 3.141592653589793
double square(double x)
{
return x * x;
}
int main(void)
{
double x1,y1,x2,y2,x3,y3;
double a2,b2,c2;
double r;
while(scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3) != EOF)
{
a2 = square(x1 - x2) + square(y1 - y2);
b2 = square(x1 - x3) + square(y1 - y3);
c2 = square(x3 - x2) + square(y3 - y2);
r = sqrt(c2/(1 - square(a2 + b2 - c2)/a2/b2/4))/2;
printf("%.2f\n",2 * PI * r);
}
}