#include<stdio.h>
#include<math.h>
//1125 求三角形的面积
double z(double x1, double y1,double x2,double y2) {
return sqrt((x1-x2)*(x1-x2) + (y1-y2) * (y1-y2));
}//三角形的边长
int main() {
double x1, x2, x3, y1, y2, y3;
while(scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&...