class vector: private point
{
public:
	vector();
	vector(double x, double y);
	double length() const;
	double x() const;
	double y() const;
	void print_vector();
};


class fancy_triangle: public triangle
{
public:
	fancy_triangle();
	fancy_triangle(point p1, point p2, point p3);
	void set_color(int color);
	void shift(vector v);
    fancy_triangle rotate(double theta);               // use default center
	fancy_triangle rotate(double theta, point C); // use c as center;
private:
	int my_color;
	point rotate_oneP(double theta, point P,  point center);
};