expm1
double expm1(double);
extern double expm1(double);
extern double expm1(double);
t = expm1(w);
t = expm1(r);
z = one - two / (expm1(t + t) + two);
y = expm1(-t - t);
return ((float) expm1((double) x));
t = expm1(x + x);