[m^3]

Correct me if I'm wrong, but this seems right:

x = (1 + e^y) / (1 - e^y)
x(1 - e^y) = (1 + e^y)
x - x(e^y) = 1 + e^y
x - 1 = e^y + x(e^y)
x - 1 = (x + 1)(e^y)
(x - 1) / (x + 1) = e^y
y = ln( (x - 1) / (x + 1) )

first post =P