Two circuit groups with different resistances can be connected with less loss over a coil and a capacitor.
It is not necessary, that the output resistor is a resistance.
It can be also a reactance.
The script calculate only LC networks with low-pass characteristic.
Such LC networks are in use in antenna tuners.
The calculated values of the LC networks are valid always only for one frequency, since the used parts are frequency-dependent.
The calculation of reactances of a coil or a capacitor is possible on an separate webpage.
In the first part the script calculates the LC network correspondent to a prefered reactance. This reactance is for example measure with an antenna analyzer.
In the second part the script calculates the reactances correspondent the prefered LC network. On this way it is for example possible to calculate the antenna impedance, if the inserted coils and capacitors of the for the match used antenna tuner are know.
If you want to know, how looks the equations used into the script, then see at the mathematical background : LC network, CL network.
 Norbert Graubner, DL1SNG: Transformation mit LC-Gliedern − Funktion von Antennenkopplern. Funkamateur 3/2008, pp. 273-276