def get_point(theta_ik, theta_jk, Pi, Pj):
    """ Calculate coordinates of point Pk given two points Pi, Pj and inner angles.  :param theta_ik: Inner angle at Pi to Pk.
    :param theta_jk: Inner angle at Pj to Pk.
    :param Pi: Coordinates of point Pi.
    :param Pj: Coordinates of point Pj.

    :return: Coordinate of point Pk.
    """
    A = np.array([[sin(theta_ik), -cos(theta_ik)],
                  [sin(theta_jk), -cos(theta_jk)]])
    B = np.array([[sin(theta_ik), -cos(theta_ik), 0, 0],
                  [0, 0, sin(theta_jk), -cos(theta_jk)]])
    p = np.r_[Pi, Pj]
    Pk = np.linalg.solve(A, np.dot(B, p))
    return Pk