public Math_Vector rotate(double angle){
  double rad=angle * TO_RADIANS;
  double cos=Math.cos(rad);
  double sin=Math.sin(rad);
  double newX=this.x * cos - this.y * sin;
  double newY=this.x * sin + this.y * cos;
  this.x=newX;
  this.y=newY;
  return this;
}

public Math_Vector rotate ( double angle ) { double rad = angle * TO_RADIANS ; double cos = Math . cos ( rad ) ; double sin = Math . sin ( rad ) ; double newX = this . x * cos - this . y * sin ; double newY = this . x * sin + this . y * cos ; this . x = newX ; this . y = newY ; return this ; }
rotate the vector using angle
