If you know the answer you should simply differentiate the answer and see if it fits.
Anyway,
∫(exp(2x) - 1)/(exp(2x) + 1) dx =
∫(exp(x) - exp(-x))/(exp(x) + exp(-x)) dx =
∫(exp(x) - exp(-x))/2 /(exp(x) + exp(-x))/2 dx =
∫sh(x) / ch(x) dx =
∫th(x) dx =
ln(ch(x))