\frac{x - \sin x}{x - \tan x}\begin{array}{l}
\mathbf{if}\;x \le -2.422154288730760107739570230478420853615 \lor \neg \left(x \le 2.458140845788107320402104960521683096886\right):\\
\;\;\;\;\left(\frac{\sin x}{x \cdot \cos x} + \left(\frac{{\left(\sin x\right)}^{2}}{{x}^{2} \cdot {\left(\cos x\right)}^{2}} + 1\right)\right) - \left(\frac{\sin x}{x} + \frac{{\left(\sin x\right)}^{2}}{{x}^{2} \cdot \cos x}\right)\\
\mathbf{else}:\\
\;\;\;\;\left(\frac{9}{40} \cdot {x}^{2} - \frac{27}{2800} \cdot {x}^{4}\right) - \frac{1}{2}\\
\end{array}double f(double x) {
double r19539 = x;
double r19540 = sin(r19539);
double r19541 = r19539 - r19540;
double r19542 = tan(r19539);
double r19543 = r19539 - r19542;
double r19544 = r19541 / r19543;
return r19544;
}
double f(double x) {
double r19545 = x;
double r19546 = -2.42215428873076;
bool r19547 = r19545 <= r19546;
double r19548 = 2.4581408457881073;
bool r19549 = r19545 <= r19548;
double r19550 = !r19549;
bool r19551 = r19547 || r19550;
double r19552 = sin(r19545);
double r19553 = cos(r19545);
double r19554 = r19545 * r19553;
double r19555 = r19552 / r19554;
double r19556 = 2.0;
double r19557 = pow(r19552, r19556);
double r19558 = pow(r19545, r19556);
double r19559 = pow(r19553, r19556);
double r19560 = r19558 * r19559;
double r19561 = r19557 / r19560;
double r19562 = 1.0;
double r19563 = r19561 + r19562;
double r19564 = r19555 + r19563;
double r19565 = r19552 / r19545;
double r19566 = r19558 * r19553;
double r19567 = r19557 / r19566;
double r19568 = r19565 + r19567;
double r19569 = r19564 - r19568;
double r19570 = 0.225;
double r19571 = r19570 * r19558;
double r19572 = 0.009642857142857142;
double r19573 = 4.0;
double r19574 = pow(r19545, r19573);
double r19575 = r19572 * r19574;
double r19576 = r19571 - r19575;
double r19577 = 0.5;
double r19578 = r19576 - r19577;
double r19579 = r19551 ? r19569 : r19578;
return r19579;
}



Bits error versus x
Results
if x < -2.42215428873076 or 2.4581408457881073 < x Initial program 0.0
Taylor expanded around inf 0.4
if -2.42215428873076 < x < 2.4581408457881073Initial program 62.7
Taylor expanded around 0 0.2
rmApplied associate--r+0.2
Final simplification0.3
herbie shell --seed 2019297
(FPCore (x)
:name "sintan (problem 3.4.5)"
:precision binary64
(/ (- x (sin x)) (- x (tan x))))