Equation Icon   ± 1 ± r±1 R 1 = -trr [g1] = cosh---, 2 2 ± 1- ± r±2- R 2 = 2 trr [g2] = cosh 2 , (47) ± ± ± 1- ± (r1-+-r2 ) R 12 = 2 trr [g1 .g2] = cosh 2 ,