1. The problem statement, all variables and given/known data The book has it exp(-MgbH/KT) =(sinh(2S+1)x/2)/(sinh(x/2)) for M=2S+1, and x = gbH/(kt). 2. Relevant equations 3. The attempt at a solution I'd have it as cosh(Mx)-sinh(Mx). How did they get the above result? Help please. Thanks.