2774: 计算三角形面积

参考代码:

#include<bits/stdc++.h>

using namespace std;

int main()

{

    double a;

    cin>>a>>b>>c>>d>>e>>f;

    double s=sqrt((a-c)*(a-c)+(b-d)*(b-d));

    double x=sqrt((a-e)*(a-e)+(b-f)*(b-f));

    double y=sqrt((c-e)*(c-e)+(d-f)*(d-f));

    double z=(s+x+y)/2;

    printf("%.2lf",sqrt(z*(z-s)*(z-x)*(z-y)));

    return 0;

}