Friend function

#include <iostream>
#include <math.h>
#include <Windows.h>
#include <conio.h>
 
using namespace std;
 
#define PI 3.14
 
class Section1
{
    private:
        double X,Y;
        double X1,Y1;   
 
public:
    Section1();
    Section1(double X, double X1, double Y, double Y1)
    {
        this->X = X;
        this->Y = Y;
        this->X1 = X1;
        this->Y1 = Y1;
    }
    void Angle();
    void Length();  
};
 
void Section1::Length()
{
    double Len = sqrt(pow(X1 - X, 2) + pow(X1 - X, 2));
    
    cout << "Length: " << Len << endl;
}
 
void Section1::Angle()
{
    double Angle = atan(abs(X - X1) / abs(Y - Y1)) * 180 / PI;
 
    cout << "Angle with axis OX: " << Angle << endl;
}

#include "stdafx.h"
#include "Sect.h"
 
 
int _tmain(int argc, _TCHAR* argv[])
{
    Section1 A(30,50, 60,90);
 
    A.Length();
    A.Angle();
    return 0;
}

 
 
 
virtual ~Section() = 0;
virtual   void Angle();
   virtual void Length();

class Section2 : public Selection1
{
    private:
*** 
 
public:
***
 
    void Angle();
    void Length();  
};

void Section1::Angle()
{
    double Angle = atan(abs(X - X1) / abs(Y - Y1)) * 180 / PI;
 
    cout << "Angle with axis OX: " << Angle << endl;
}
 
*****
void Section2::Angle()
{
   Section1::Angle();
}

  ********
  friend  Angle();
    friend  Length();  
};
 
Section1::Length()
{
    double Len = sqrt(pow(X1 - X, 2) + pow(X1 - X, 2));
    
    cout << "Length: " << Len << endl;
}
 
Section1::Angle()
{
    double Angle = atan(abs(X - X1) / abs(Y - Y1)) * 180 / PI;
 
    cout << "Angle with axis OX: " << Angle << endl;
}

    friend void Angle();
    friend void Length();   
};
 
Section1::Length()
{
    double Len = sqrt(pow(X1 - X, 2) + pow(X1 - X, 2));
    
    cout << "Length: " << Len << endl;
}
 
Section1::Angle()
{
    double Angle = atan(abs(X - X1) / abs(Y - Y1)) * 180 / PI;
 
    cout << "Angle with axis OX: " << Angle << endl;
}

friend void Length(const Section1 & se);   
};
 
void Length(const Section1 & se)
{
    double Len = sqrt(se.X1 - se.X, 2) + pow(se.X1 - se.X, 2));
    
    cout << "Length: " << Len << endl;
}

Length(A);