Multi-value problems in the transmission / reflection method have been attached much attention. In this work,two types of formula determining permittivity and permeability from scattering coefficients are considered,it is shown that,under conditions of imaginary part of refraction index not smaller than zero,real part of impedance larger than zero and relationship of tangent angle of refraction index limited by that of impedance,both the two approaches may determine impedance and imaginary part of refractio...