_________ \/ sech(x)
sqrt(sech(x))
_________ -\/ sech(x) *tanh(x) --------------------- 2
_________ / 2 \ \/ sech(x) *\-2 + 3*tanh (x)/ ----------------------------- 4
_________ / 2 \ -\/ sech(x) *\-14 + 15*tanh (x)/*tanh(x) ----------------------------------------- 8