Sector matrix in X

    :param theta: bend angle, in [rad]
    :param rho: bend radius, in [m]
    :return: 2x2 numpy array

def funTransSectX(theta, rho):
    """ Sector matrix in X

    :param theta: bend angle, in [rad]
    :param rho: bend radius, in [m]
    :return: 2x2 numpy array
    """
    return np.matrix([[np.cos(theta), rho * np.sin(theta)], [-np.sin(theta) / rho, np.cos(theta)]], dtype=np.double)