1. The problem statement, all variables and given/known data 2. Relevant equations (above) 3. The attempt at a solution I know that x=tanh(y) can be shown as y=tanh^-1(x). The problem is how do i get from there to the next part. I'm kinda stuck here. I can show that x = sinh(y)/cosh(y) x = (e^y - e^-y) / (e^y + e^-y) x = lny (1+y)/(1-y) I know something is terribly wrong in the last step. and I dont think this is the way to proceed with the question. Can you help me out?