public Vector rotateInRadian(double radians){
  final double length=length();
  double angle=angleInRadian();
  angle+=radians;
  final Vector result=new Vector(Math.cos(angle),Math.sin(angle));
  return result.multiply(length);
}

public Vector rotateInRadian ( double radians ) { final double length = length ( ) ; double angle = angleInRadian ( ) ; angle += radians ; final Vector result = new Vector ( Math . cos ( angle ) , Math . sin ( angle ) ) ; return result . multiply ( length ) ; }
return a new instance of vector rotated from the given number of radians .
