sh := (exp(x) - exp(-x)) / 2;
ch := (exp(x) + exp(-x)) / 2;
th := (exp(x) - exp(-x)) / (exp(x) + exp(-x));
cth := (exp(x) + exp(-x)) / (exp(x) - exp(-x));
sch := 2 / (exp(x) + exp(-x));
csch := 2 / (exp(x) - exp(-x));