信息学奥赛一本通 1034：计算三角形面积

刷题目录

#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int main()
{
double x1,x2,x3,y1,y2,y3,p,s,a,b,c;
cout.precision(2);
cin>>x1>>y1>>x2>>y2>>x3>>y3;
a=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
b=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2)); 
c=sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
p=(a+b+c)/2;
s=sqrt(p*(p-a)*(p-b)*(p-c));
cout<<fixed<<s; 
return 0;
}