\frac{1 - \cos x}{x \cdot x}\begin{array}{l}
\mathbf{if}\;x \le -0.031454960231223988 \lor \neg \left(x \le 0.033122201796403697\right):\\
\;\;\;\;\frac{1}{x} \cdot \frac{1 - \cos x}{x}\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left({x}^{4}, \frac{1}{720}, \frac{1}{2} - \frac{1}{24} \cdot {x}^{2}\right)\\
\end{array}double f(double x) {
double r21794 = 1.0;
double r21795 = x;
double r21796 = cos(r21795);
double r21797 = r21794 - r21796;
double r21798 = r21795 * r21795;
double r21799 = r21797 / r21798;
return r21799;
}
double f(double x) {
double r21800 = x;
double r21801 = -0.03145496023122399;
bool r21802 = r21800 <= r21801;
double r21803 = 0.0331222017964037;
bool r21804 = r21800 <= r21803;
double r21805 = !r21804;
bool r21806 = r21802 || r21805;
double r21807 = 1.0;
double r21808 = r21807 / r21800;
double r21809 = 1.0;
double r21810 = cos(r21800);
double r21811 = r21809 - r21810;
double r21812 = r21811 / r21800;
double r21813 = r21808 * r21812;
double r21814 = 4.0;
double r21815 = pow(r21800, r21814);
double r21816 = 0.001388888888888889;
double r21817 = 0.5;
double r21818 = 0.041666666666666664;
double r21819 = 2.0;
double r21820 = pow(r21800, r21819);
double r21821 = r21818 * r21820;
double r21822 = r21817 - r21821;
double r21823 = fma(r21815, r21816, r21822);
double r21824 = r21806 ? r21813 : r21823;
return r21824;
}



Bits error versus x
if x < -0.03145496023122399 or 0.0331222017964037 < x Initial program 1.0
rmApplied add-exp-log1.0
rmApplied *-un-lft-identity1.0
Applied log-prod1.0
Applied exp-sum1.0
Applied times-frac0.5
Simplified0.5
Simplified0.5
if -0.03145496023122399 < x < 0.0331222017964037Initial program 62.2
Taylor expanded around 0 0.0
Simplified0.0
Final simplification0.3
herbie shell --seed 2020081 +o rules:numerics
(FPCore (x)
:name "cos2 (problem 3.4.1)"
:precision binary64
(/ (- 1 (cos x)) (* x x)))