@staticmethod
def _circleEquation(pt1, pt2, pt3):
    """Circle equation from 3 (x, y) points

        :return: Position of the center of the circle and the radius
        :rtype: Tuple[Tuple[float,float],float]
        """
    x, y, z = complex(*pt1), complex(*pt2), complex(*pt3)
    w = z - x
    w /= y - x
    c = (x - y) * (w - abs(w) ** 2) / 2.0j / w.imag - x
    return (-c.real, -c.imag), abs(c + x)
