Создать класс "точка" и производный класс "отрезок"

#include <iostream> 
#include <complex> 
using namespace std; 
 
class tochka
{ 
private: double x1,x2,y1,y2; 
public: 
tochka (double,double,double,double); 
~tochka(); 
double d(); 
}; 
tochka ::tochka (double x1, double x2, double y1,double y2) 
{ 
tochka ::x1=xn; 
tochka ::x2=xk; 
tochka ::y1=yn; 
tochka ::y2=yk;
} 
tochka ::~tochka() 
{
}
 
 
int main() 
{ 
double xn,yn,xk,yk; 
cout<<"xn= \n"; 
cin >>xn; 
cout<<"yn= \n"; 
cin>>yn; 
cout<<"xk= \n"; 
cin>>xk;
cout<<"yk= \n";
cin>>yk;
tochka ob(x1,y1,x2,y2); 
 
system("pause"); 
return 0; 
}

#include <iostream>
#include <cmath>
 
class point
{
protected:
    double _x, _y;
public:
    point(double xn, double yn)
        : _x(xn), _y(yn) {}
    double x() {return _x;}
    double y() {return _y;}
};
 
class intercept: public point
{
    double _x1, _y1;
    double _length;
public:
    intercept(double x0, double y0, double x1, double y1)
        : point(x0, y0), _x1(x1), _y1(y1)
    {
        _length=sqrt((_x1-_x)*(_x1-_x)+(_y1-_y)*(_y1-_y));
    }
    double x1() {return _x1;}
    double y1() {return _y1;}
    double length() {return _length;}
};
 
int main()
{
    intercept i(13, 9, 1, 4);
    std::cout << i.length() << std::endl;
    system("pause");
    return 0;
}

class intercept
{
    point   _p0, _p1;
    double  _length;
public:
    intercept(double x0, double y0, double x1, double y1)
        : _p0(x0, y0), _p1(x1, y1)
    {
        _length=sqrt((_p0.x()-_p1.x())*(_p0.x()-_p1.x())+(_p0.y()-_p1.y())*(_p0.y()-_p1.y()));
    }
    point p0() {return _p0;}
    point p1() {return _p1;}
    double length() {return _length;}
};

#include <iostream> 
#include <complex> 
using namespace std; 
 
class uravnenie 
{ 
private: double a,b,c; 
public: 
uravnenie (double,double,double); 
~uravnenie (); 
double x1(); 
double x2(); 
}; 
uravnenie ::uravnenie (double a1, double b1, double c1) 
{ 
uravnenie ::a=a1; 
uravnenie ::b=b1; 
uravnenie ::c=c1; 
} 
uravnenie ::~uravnenie () 
{ 
} 
double uravnenie ::x1() 
{ 
return ((-b+sqrt(b*b-4*a*c))/(2*a)); 
} 
double uravnenie ::x2() 
{ 
return ((-b-sqrt(b*b-4*a*c))/(2*a)); 
} 
int main() 
{ 
double a1,b1,c1; 
cout<<"a= \n"; 
cin >>a1; 
cout<<:b= \n"; 
cin>>b1; 
cout<<"c= \n"; 
cin>>c1; 
 uravnenie ob(a1,b1,c1); 
cout<<"X1="<<ob.x1()<<" "<<"X2=" 
<<ob.x2()<<"\n"; 
system("pause"); 
return 0; 
}

#include <iostream>
#include <cmath>
#include "conio.h"
using namespace std;
 
 
 
class point
{
protected:
        double _x, _y;
public:
        point(double xn, double yn)
                : _x(xn), _y(yn) {}
        double x() {return _x;}
        double y() {return _y;}
};
 
class intercept: public point
{
        double _x1, _y1;
        double _length;
public:
        intercept(double x0, double y0, double x1, double y1)
                : point(x0, y0), _x1(x1), _y1(y1)
        {
                _length=sqrt((_x1-_x)*(_x1-_x)+(_y1-_y)*(_y1-_y));
        }
        double x1() {return _x1;}
        double y1() {return _y1;}
        double length() {return _length;}
};
 
int main()
{
    cout<<"Vvedite xn= \n";
    cin>>x0;
    cout<<"Vvedite yn= \n";
    cin>>y0;
    cout<<"Vvedite xk= \n";
    cin>>x1;
    cout<<"Vvedite yk= \n";
    cin>>y1;
 
 
        intercept i(x0,y0,x1,y1);
        std::cout << i.length() << std::endl;
        system("pause");
    return 0;
}