#include<iostream.h>
#include<math.h>
class tria;
class cpoint
{
int x1,y1,x2,y2,x3,y3;
public:
cpoint(int a1,int b1,int a2,int b2,int a3,int b3) {
x1=a1;
y1=b1;
x2=a2;
y2=b2;
x3=a3;
y3=b3;
}
void change(tria &);
};
class tria
{
double d1,d2,d3,p;
public:
tria(int a1,int b1,int a2,int b2,int a3,int b3 )
{
d1=sqrt((a1-a2)*(a1-a2)+(b1-b2)*(b1-b2));
d2=sqrt((a1-a3)*(a1-a3)+(b1-b3)*(b1-b3));
d3=sqrt((a2-a3)*(a2-a3)+(b2-b3)*(b2-b3));
p=(d1+d2+d3)/2;
}
double mianji()
{
return sqrt(p*(p-d1)*(p-d2)*(p-d3));
}
friend void cpoint::change(tria &);
};
void cpoint::change(tria &c)
{
cout<<"这个三角形面积为"<<c.mianji()<<endl;
}
void main()
{
int a1,b1,a2,b2,a3,b3;
for(int i=0;;i++)
{
cout<<"请输入一个点的信息"<<endl;
cin>>a1>>b1;
cout<<"请输入第二个点的信息"<<endl;
cin>>a2>>b2;
cout<<"请输入第三个点的信息"<<endl;
cin>>a3>>b3;
cpoint cp(a1,b1,a2,b2,a3,b3);
tria c(a1,b1,a2,b2,a3,b3);
cp.change(c);
int j;
cout<<"如果要继续输入请按1否则按0"<<endl;
cin>>j;
if(j)
continue;
else
break;
}
}