code: def rotate(self, angle):
          
          perp = Vector(-self.y, self.x)
          angle = angle * math.pi / 180.0
          c, s = math.cos(angle), math.sin(angle)
          return Vector(self.x * c + perp.x * s, self.y * c + perp.y * s)
docs: Rotates self counterclockwise by angle 
          (the angle must be given in a 360 degree system)