Rotate the given vector by an angle. Angle measured in radians counter-clockwise.

def rotate(self, angle):
        """ Rotate the given vector by an angle. Angle measured in radians counter-clockwise. """
        x, y = self.tuple
        self.x = x * math.cos(angle) - y * math.sin(angle)
        self.y = x * math.sin(angle) + y * math.cos(angle)