R a = R 1 R 2 + R 2 R 3 + R 3 R 1 R 2 {\displaystyle R_{\mathrm {a} }={\frac {R_{1}R_{2}+R_{2}R_{3}+R_{3}R_{1}}{R_{2}}}} R b = R 1 R 2 + R 2 R 3 + R 3 R 1 R 3 {\displaystyle R_{\mathrm {b} }={\frac {R_{1}R_{2}+R_{2}R_{3}+R_{3}R_{1}}{R_{3}}}} R c = R 1 R 2 + R 2 R 3 + R 3 R 1 R 1 {\displaystyle R_{\mathrm {c} }={\frac {R_{1}R_{2}+R_{2}R_{3}+R_{3}R_{1}}{R_{1}}}} </math>