#include <iostream>
#include "Triangle.h"
using namespace std;

int main()
{
    Triangle T1;
    T1.a = 2;
    T1.b = 3;
    T1.c = 4;
    T1.print();
    Triangle *T2 = new Triangle(3 , 4, 5);
    T2->print();
    cout << "Obwod = " << T2->circuit() << endl;;

    Point A, B, C;
    A.x = 1; A.y = 2;
    B.x = 5; B.y = 4;
    C.x = 3; C.y = -2;

    Triangle *T3 =  new Triangle(A, B, C);
    T3->print();

    Triangle *T4 = new Triangle(Point(1,2), Point(5,4), Point(3,-2));
    T4->print();
    cout << "Pole: " << T4->area();
    return 0;
}

---------------------------------------------------------------------------------------

#ifndef TRIANGLE_H
#define TRIANGLE_H
#include "Point.h"

class Triangle
{
    public:
        double a;
        double b;
        double c;

    public:
        Triangle();
        Triangle(double a, double b, double c);
        Triangle(Point A, Point B, Point C);
        ~Triangle();
        void print();
        double circuit();
        static double section(Point A, Point B);
        double area();
    protected:

    private:
};

#endif // TRIANGLE_H

------------------------------------------------------------------------------------

#include "Triangle.h"
#include <iostream>
#include <cmath>

using namespace std;

Triangle::Triangle()
{
    //ctor
}

Triangle::Triangle(double a, double b, double c)
{
    this->a = a;
    this->b = b;
    this->c = c;
}

Triangle::Triangle(Point A, Point B, Point C)
{
    a = section(A,B);
    b = section(A,C);
    c = section(B,C);
}

Triangle::~Triangle()
{
    //dtor
}
void Triangle::print()
{
    cout << "Trojkat o bokach: " << a << ", " << b << ", " << c << endl;
}

double Triangle::circuit()
{
    return a+b+c;
}

double Triangle::section(Point A, Point B)
{
    return sqrt(pow(B.x-A.x,2) + pow(B.y-A.y,2));
}

double Triangle::area()
{
    double p =(a+b+c)/2;
    return sqrt(p*(p-a)*(p-b)*(p-c));
}

---------------------------------------------------------------------------

#ifndef POINT_H
#define POINT_H


class Point
{
    public:
        int x;
        int y;

    public:
        Point();
        Point(int x, int y);
        ~Point();

};

#endif // POINT_H

-----------------------------------------------------------------------------

#include "Point.h"

Point::Point()
{
    x = 0;
    y = 0;
}
Point::Point(int x, int y)
{
    this->x = x;
    this->y = y;
}
Point::~Point()
{
    //dtor
}