{\displaystyle {\begin{aligned}R_{z}&={\frac {Z_{11}Z_{22}-Z_{21}^{2}}{Z_{21}}}\\R_{x}&={\frac {Z_{11}Z_{22}-Z_{21}^{2}}{Z_{22}-Z_{21}}}\\R_{y}&={\frac {Z_{11}Z_{22}-Z_{21}^{2}}{Z_{11}-Z_{21}}}\end{aligned}}}