functions.h
-----------
#include <iostream>
#include <iomanip>
#include <conio.h>
#include <stdlib.h>
using namespace std;

#include "figure.h"

void zada4a();
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figure.h
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class point{
private:
    double x;
    double y;
public:
    point(): x(0), y(0){}
    point(int, int);
    friend class figure;
    friend istream& operator >> (istream& s, point& d);
};

class figure{
private:
    point koor, koor1, koor2, koor3;
    static char nazv[10];
    static int total;
    int t;
public:
    figure();                  //Конструктор по умолчанию
    figure( point kor, point kor1, point kor2, point kor3 );
    figure( const figure&);
    ~figure(){
        total--;
    }
    void proverka(figure&);


};
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main.cpp
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#include "functions.h"

void main(){
    setlocale(0, "RUS");
    zada4a();
    system("pause");
    return;
}
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functions.cpp
------------
#include "functions.h"

void zada4a(){
    figure a1, a2,a5;
    point a(1,1), b(4,4), c(6,4), d(9,1);
    point aa1(1,1), bb1(2,4), cc1(6,4), dd1(9,1);
    figure ak(a,b,c,d);
    figure ak1(aa1,bb1,cc1,dd1);
    ak.proverka(ak);
    ak1.proverka(ak1);
    figure ab(ak);
return;
}
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figure.cpp
------------
#include "functions.h"

point::point(int m_x, int m_y){
    x = m_x;
    y = m_y;
}

figure::figure(): koor(0,0), koor1(0,0), koor2(0,0), koor3(0,0){
    total++;
    cout << nazv << " " << total << " ";
}                     //Конструктор по умолчанию
figure::figure( point kor, point kor1, point kor2, point kor3 ){
    koor=kor;
    koor1=kor1;
    koor2=kor2;
    koor3=kor3;
    total++;
    cout << nazv << " " << total<< " ";
}
figure::figure( const figure&  A ){
    koor=A.koor;
    koor1=A.koor1;
    koor2=A.koor2;
    koor3=A.koor3;
    cout << endl << "Конструктор копирования " << endl;
}

istream& operator>>(istream& s, point& d){
    s >> d.x;
    return s;
}

void figure::proverka(figure& A){
    koor=A.koor;
    koor1=A.koor1;
    koor2=A.koor2;
    koor3=A.koor3;
    double AC = sqrt(pow(koor.x - koor2.x, 2) + pow(koor.y - koor2.y, 2));
    double BD = sqrt(pow(koor1.x - koor3.x, 2) + pow(koor1.y - koor3.y, 2));
    double AB = sqrt(pow(koor.x - koor1.x, 2) + pow(koor.y - koor1.y, 2));
    double AD = sqrt(pow(koor.x - koor3.x, 2) + pow(koor.y - koor3.y, 2));
    double BC = sqrt(pow(koor1.x - koor2.x, 2) + pow(koor1.y - koor2.y, 2));
    if (AC==BD){
        cout << endl << "Трапеция равнобедренная " << endl;
        double h = sqrt(pow(AB,2)-((pow(BC-AD,2))/4));
        double S = h*(BC+AD)/2;
        cout << "Площадь трапеции - " << S << endl << "Высота трапеции - " << h << endl;
    }
    else{
        cout << endl << "Трапеция не равнобедренная " << endl;
        double Perimetr = AB*2+AD+BC;
        cout << "Периметр трапеции равен " << Perimetr <<endl;
    }
}

char figure::nazv[10] = "Трапеция\0";
int figure::total = 0;