Graphing a Rotated Ellipse

[Cory Wolfe]

So i have code to draw an Ellipse, but I need to modify it so i can rotate it about an angle (namely, 45 deg) but can't seem to figure it out. If you can show me how to do this, I would appreciate it.

struct Ellipse : Shape {
    Ellipse(Point p, int w, int h)    // center, min, and max distance from center
        : w(w), h(h)
    { 
        add(Point(p.x-w,p.y-h));
    }

    void draw_lines() const;

    Point center() const { return Point(point(0).x+w,point(0).y+h); }
    Point focus1() const { return Point(center().x+int(sqrt(double(w*w-h*h))),center().y); }
    Point focus2() const { return Point(center().x-int(sqrt(double(w*w-h*h))),center().y); }

    void set_major(int ww) { w=ww; }
    int major() const { return w; }
    void set_minor(int hh) { h=hh; }
    int minor() const { return h; }
private:
    int w;
    int h;
};

[olivthill2]

See http://www.codeguru.com/forum/showthread.php?t=369834