How to write a C++ constructor that rotates a rectangle?

I am trying to write a constructor that takes in a point, width and height of the rectangle, and an angle. But I couldn't figure our a way of doing it. I tried several ways but they don't work. Here's what I've got so far:

Rectangle::Rectangle(){
   corner1 = Point(0,0);
   corner2 = Point(0,-1);
   corner3 = Point(1,-1);
   corner4 = Point(1,0);
   }  //default constructor

Rectangle::Rectangle(Point c, double w, double h){
   corner1 = c;
   corner2 = Point(c.get_x(),c.get_y()-h);
   corner3 = Point(c.get_x()+w,c.get_y()-h);
   corner4 = Point(c.get_x()+w,c.get_y());
   }

Rectangle::Rectangle(Point c, double w, double h, double a){
   } //the part that's troubling me

I've also written these, which could be helpful (but I'm not sure how to use them):

void Rectangle::rotate(double a){ //rotate a rectangle
   double xmove = get_center().get_x();
   double ymove = get_center().get_y();
   move(-xmove,-ymove);

   rotatePoint(corner1,a);
   rotatePoint(corner2,a);
   rotatePoint(corner3,a);
   rotatePoint(corner4,a);

   move(xmove,ymove);
   return;
    } //if somehow I can use this it would be great

void Rectangle::rotatePoint(Point& p, double a){
    double new_x = p.get_x()*cos(a*PI/180)-p.get_y()*sin(a*PI/180);
    double new_y = p.get_x()*sin(a*PI/180)+p.get_y()*cos(a*PI/180);
    p = Point(new_x,new_y);
   return;
   }

Thank you very much.