\frac{x - \sin x}{x - \tan x}\begin{array}{l}
\mathbf{if}\;x \le -0.01665811831216180982639940566514269448817:\\
\;\;\;\;\frac{1}{\frac{x}{x - \sin x} - \frac{\tan x}{x - \sin x}}\\
\mathbf{elif}\;x \le 0.01529116643609437255213467921066694543697:\\
\;\;\;\;\frac{1}{\left(-{x}^{4} \cdot \frac{81}{100}\right) + \left(-\left(-\left(\frac{513}{1400} \cdot {x}^{4} + 2\right) \cdot \left(\frac{513}{1400} \cdot {x}^{4} + 2\right)\right)\right)} \cdot \left(\frac{9}{10} \cdot {x}^{2} - \left(\frac{513}{1400} \cdot {x}^{4} + 2\right)\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{1}{\frac{x - \tan x}{x - \sin x}}\\
\end{array}double f(double x) {
double r13549 = x;
double r13550 = sin(r13549);
double r13551 = r13549 - r13550;
double r13552 = tan(r13549);
double r13553 = r13549 - r13552;
double r13554 = r13551 / r13553;
return r13554;
}
double f(double x) {
double r13555 = x;
double r13556 = -0.01665811831216181;
bool r13557 = r13555 <= r13556;
double r13558 = 1.0;
double r13559 = sin(r13555);
double r13560 = r13555 - r13559;
double r13561 = r13555 / r13560;
double r13562 = tan(r13555);
double r13563 = r13562 / r13560;
double r13564 = r13561 - r13563;
double r13565 = r13558 / r13564;
double r13566 = 0.015291166436094373;
bool r13567 = r13555 <= r13566;
double r13568 = 4.0;
double r13569 = pow(r13555, r13568);
double r13570 = 0.81;
double r13571 = r13569 * r13570;
double r13572 = -r13571;
double r13573 = 0.36642857142857144;
double r13574 = r13573 * r13569;
double r13575 = 2.0;
double r13576 = r13574 + r13575;
double r13577 = r13576 * r13576;
double r13578 = -r13577;
double r13579 = -r13578;
double r13580 = r13572 + r13579;
double r13581 = r13558 / r13580;
double r13582 = 0.9;
double r13583 = pow(r13555, r13575);
double r13584 = r13582 * r13583;
double r13585 = r13584 - r13576;
double r13586 = r13581 * r13585;
double r13587 = r13555 - r13562;
double r13588 = r13587 / r13560;
double r13589 = r13558 / r13588;
double r13590 = r13567 ? r13586 : r13589;
double r13591 = r13557 ? r13565 : r13590;
return r13591;
}



Bits error versus x
Results
if x < -0.01665811831216181Initial program 0.1
rmApplied clear-num0.1
rmApplied div-sub0.1
if -0.01665811831216181 < x < 0.015291166436094373Initial program 63.2
rmApplied clear-num63.2
Taylor expanded around 0 0.0
rmApplied flip-+0.0
Applied distribute-neg-frac0.0
Applied associate-/r/0.0
Simplified0.0
if 0.015291166436094373 < x Initial program 0.1
rmApplied clear-num0.1
Final simplification0.1
herbie shell --seed 2019354
(FPCore (x)
:name "sintan (problem 3.4.5)"
:precision binary64
(/ (- x (sin x)) (- x (tan x))))