Derivation of Marchand Balun equations

Could anyone advise about derivation of Marchand Balun Equations ?

Note: Screenshot below is taken from paper :

New Design Formulas for Impedance-Transforming 3-dB Marchand Baluns

Analysis and design of impedance-transforming planar Marchand baluns talks about the derivation process, but it is still not complete.

We still need to derive equation (1) of the paper.

We?
Only you.
Simply learn very basic math and microwave theory.