Summarizing the derivation result from reply #3 and reply #5 , we could derive equation (5.3) easily.
However, what I do not understand is why the extra term for the inductor equation (5.3) is labeled as "shunt susceptance of the high-impedance line" ?
If I am not wrong, the book might have a typo mistake and the correct version of the sentence should be as follows :
The results of Eq. (5.2) do not take into account the series reactance of the HIGH-impedance line and shunt susceptance of the LOW-impedance lines.