杭电acm the area

#include<iostream>
#include<cstdio>
using namespace std;
int main(){
	int t;
	scanf("%d",&t);
	while(t--){
	double x1,y1,x2,y2,x3,y3;
	  cin>>x1>>y1>>x2>>y2>>x3>>y3;
	  double k = (y3-y2)/(x3-x2);
	  double m = y2-k*x2;
	  double k1=(y2-y1)/((x2-x1)*(x2-x1));
	  double a = k1;
	  double b = -2*a*x1;
	  double c = a*x1*x1+y1;
	  double s =
				a/3*(x3*x3*x3-x2*x2*x2)+
				0.5*(b-k)*(x3*x3-x2*x2)+(c-m)*(x3-x2);
		printf("%.2f\n",s);
	}
}