(1) PaVaPcVcamp;=PbVb.... (i)amp;=PdVd.... (ii)
(2) PaVaγ−1PbVbγ−1amp;=PdVdγ−1.... (iii)amp;=PcVcγ−1.... (iv)
amp; (i) ÷ (iii) ⇒Vaγ−1Va=PdVdγ−1PbVb (v) amp; (ii) ÷ (iv) ⇒Vcγ−1Vc=PbVbγ−1PdVd (vi) amp; (v) × (vi) ⇒Vaγ−1VaVcγ−1Vc=PdVdγ−1PbVb×PbVbγ−1PdVdamp;⇒Vaγ−2Vcγ−2=Vdγ−1Vbγ−2amp;⇒VdVa=VcVb