Maxima is unable to compute the limit of (exp(a*x)-1)/(exp(a*x)+1) as x -> inf. Maxima asks if a is positive or negative or zero. If you answer positive or negative, it returns the noun form. Perversely if you answer zero, the limit is -1. But if a is zero, the expression is exactly 0.
If a number is substituted for a, then maxima correctly returns 1 or -1 depending on the sign of a.