\sqrt{\frac{e^{2 \cdot x} - 1}{e^{x} - 1}}\begin{array}{l}
\mathbf{if}\;x \le -1.109419166854957547087282512125511104578 \cdot 10^{-10}:\\
\;\;\;\;\sqrt{\frac{e^{2 \cdot x} - 1}{e^{x + x} - 1 \cdot 1}} \cdot \sqrt{e^{x} + 1}\\
\mathbf{else}:\\
\;\;\;\;\sqrt{2 + x \cdot \left(0.5 \cdot x + 1\right)}\\
\end{array}double f(double x) {
double r19873 = 2.0;
double r19874 = x;
double r19875 = r19873 * r19874;
double r19876 = exp(r19875);
double r19877 = 1.0;
double r19878 = r19876 - r19877;
double r19879 = exp(r19874);
double r19880 = r19879 - r19877;
double r19881 = r19878 / r19880;
double r19882 = sqrt(r19881);
return r19882;
}
double f(double x) {
double r19883 = x;
double r19884 = -1.1094191668549575e-10;
bool r19885 = r19883 <= r19884;
double r19886 = 2.0;
double r19887 = r19886 * r19883;
double r19888 = exp(r19887);
double r19889 = 1.0;
double r19890 = r19888 - r19889;
double r19891 = r19883 + r19883;
double r19892 = exp(r19891);
double r19893 = r19889 * r19889;
double r19894 = r19892 - r19893;
double r19895 = r19890 / r19894;
double r19896 = sqrt(r19895);
double r19897 = exp(r19883);
double r19898 = r19897 + r19889;
double r19899 = sqrt(r19898);
double r19900 = r19896 * r19899;
double r19901 = 0.5;
double r19902 = r19901 * r19883;
double r19903 = r19902 + r19889;
double r19904 = r19883 * r19903;
double r19905 = r19886 + r19904;
double r19906 = sqrt(r19905);
double r19907 = r19885 ? r19900 : r19906;
return r19907;
}



Bits error versus x
Results
if x < -1.1094191668549575e-10Initial program 0.4
rmApplied flip--0.2
Applied associate-/r/0.2
Applied sqrt-prod0.2
Simplified0.0
if -1.1094191668549575e-10 < x Initial program 36.5
Taylor expanded around 0 6.3
Simplified6.3
Final simplification0.7
herbie shell --seed 2019212
(FPCore (x)
:name "sqrtexp (problem 3.4.4)"
:precision binary64
(sqrt (/ (- (exp (* 2 x)) 1) (- (exp x) 1))))