Diem

#include <iostream>
#include <stdio.h>
#include <math.h>

using namespace std;

//khai bao lop doi tuong diem
class Diem 
{
    private: 
        float x, y;
    
    public:
        Diem();
        float operator-(Diem &d2);
        //ham ban
        friend istream& operator>>(istream &cin, Diem &d);
        friend ostream& operator<<(ostream &cout, Diem &d);
};
//===chuong trinh chinh
int main()
{
    
    //tao doi tuong diem
    Diem A,B,C;
    
    //khai bao bien
    float ab, bc, ac, chuVi;

    cout<<"Nhap vao diem A "; cin>>A;
    cout<<"Nhap vao diem B ";cin>>B ;
    cout<<"Nhap vao diem C ";cin>>C ;
    
    //tinh kc 3 canh tam giac
    ab = A - B;
    bc = B - C;
    ac = A - C;
    
    //dua ra
    cout<<"\nDiem A: "; cout<<A;
    cout<<"\nDiem B: "; cout<<B;
    cout<<"\nDiem C: "; cout<<C;
    printf("\nChu vi cua tam giac ABC la: %0.2f", ab+bc+ac);

    return 0;
}
//===dinh nghia ham===
Diem::Diem():x(0), y(0)
{
    
}

float Diem::operator-(Diem &d2)
{
    return sqrt((d2.x - x) *(d2.x - x) + (d2.y - y) * (d2.y - y));
}

//ham ban
istream& operator>>(istream &cin, Diem &d)
{
    cout<<"(dang x y): ";
    cin>>d.x>>d.y;
    
    return cin;
}

ostream& operator<<(ostream &cout, Diem &d)
{
    cout<<"("<<d.x<<" , "<<d.y<<")";
    
    return cout;
}