Average Error: 30.4 → 0.8
Time: 7.6s
Precision: binary64
\[\frac{1 - \cos x}{\sin x}\]
↓
\[\begin{array}{l} \mathbf{if}\;\frac{1 - \cos x}{\sin x} \le -0.0265199733651696155 \lor \neg \left(\frac{1 - \cos x}{\sin x} \le 3.33068334190862012 \cdot 10^{-5}\right):\\ \;\;\;\;\frac{\frac{e^{\log \left({1}^{3} - \log \left(e^{{\left(\cos x\right)}^{3}}\right)\right)}}{\cos x \cdot \left(\cos x + 1\right) + 1 \cdot 1}}{\sin x}\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{24} \cdot {x}^{3} + \left(\frac{1}{240} \cdot {x}^{5} + \frac{1}{2} \cdot x\right)\\ \end{array}\]
\frac{1 - \cos x}{\sin x}
↓
\begin{array}{l}
\mathbf{if}\;\frac{1 - \cos x}{\sin x} \le -0.0265199733651696155 \lor \neg \left(\frac{1 - \cos x}{\sin x} \le 3.33068334190862012 \cdot 10^{-5}\right):\\
\;\;\;\;\frac{\frac{e^{\log \left({1}^{3} - \log \left(e^{{\left(\cos x\right)}^{3}}\right)\right)}}{\cos x \cdot \left(\cos x + 1\right) + 1 \cdot 1}}{\sin x}\\

\mathbf{else}:\\
\;\;\;\;\frac{1}{24} \cdot {x}^{3} + \left(\frac{1}{240} \cdot {x}^{5} + \frac{1}{2} \cdot x\right)\\

\end{array}
double code(double x) {
	return ((double) (((double) (1.0 - ((double) cos(x)))) / ((double) sin(x))));
}
↓
double code(double x) {
	double VAR;
	if (((((double) (((double) (1.0 - ((double) cos(x)))) / ((double) sin(x)))) <= -0.026519973365169616) || !(((double) (((double) (1.0 - ((double) cos(x)))) / ((double) sin(x)))) <= 3.33068334190862e-05))) {
		VAR = ((double) (((double) (((double) exp(((double) log(((double) (((double) pow(1.0, 3.0)) - ((double) log(((double) exp(((double) pow(((double) cos(x)), 3.0)))))))))))) / ((double) (((double) (((double) cos(x)) * ((double) (((double) cos(x)) + 1.0)))) + ((double) (1.0 * 1.0)))))) / ((double) sin(x))));
	} else {
		VAR = ((double) (((double) (0.041666666666666664 * ((double) pow(x, 3.0)))) + ((double) (((double) (0.004166666666666667 * ((double) pow(x, 5.0)))) + ((double) (0.5 * x))))));
	}
	return VAR;
}

Error

Bits error versus x

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original30.4
Target0.0
Herbie0.8
\[\tan \left(\frac{x}{2}\right)\]

Derivation

  1. Split input into 2 regimes

  2. if (/ (- 1.0 (cos x)) (sin x)) < -0.0265199733651696155 or 3.33068334190862012e-5 < (/ (- 1.0 (cos x)) (sin x))

    1. Initial program 0.9

      \[\frac{1 - \cos x}{\sin x}\]
    2. Using strategy rm

    3. Applied flip3--1.0

      \[\leadsto \frac{\color{blue}{\frac{{1}^{3} - {\left(\cos x\right)}^{3}}{1 \cdot 1 + \left(\cos x \cdot \cos x + 1 \cdot \cos x\right)}}}{\sin x}\]

    4. Simplified1.0

      \[\leadsto \frac{\frac{{1}^{3} - {\left(\cos x\right)}^{3}}{\color{blue}{\cos x \cdot \left(\cos x + 1\right) + 1 \cdot 1}}}{\sin x}\]
    5. Using strategy rm

    6. Applied add-log-exp1.1

      \[\leadsto \frac{\frac{{1}^{3} - \color{blue}{\log \left(e^{{\left(\cos x\right)}^{3}}\right)}}{\cos x \cdot \left(\cos x + 1\right) + 1 \cdot 1}}{\sin x}\]
    7. Using strategy rm

    8. Applied add-exp-log1.1

      \[\leadsto \frac{\frac{\color{blue}{e^{\log \left({1}^{3} - \log \left(e^{{\left(\cos x\right)}^{3}}\right)\right)}}}{\cos x \cdot \left(\cos x + 1\right) + 1 \cdot 1}}{\sin x}\]

    if -0.0265199733651696155 < (/ (- 1.0 (cos x)) (sin x)) < 3.33068334190862012e-5

    1. Initial program 59.7

      \[\frac{1 - \cos x}{\sin x}\]

    2. Taylor expanded around 0 0.5

      \[\leadsto \color{blue}{\frac{1}{24} \cdot {x}^{3} + \left(\frac{1}{240} \cdot {x}^{5} + \frac{1}{2} \cdot x\right)}\]
  3. Recombined 2 regimes into one program.

  4. Final simplification0.8

    \[\leadsto \begin{array}{l} \mathbf{if}\;\frac{1 - \cos x}{\sin x} \le -0.0265199733651696155 \lor \neg \left(\frac{1 - \cos x}{\sin x} \le 3.33068334190862012 \cdot 10^{-5}\right):\\ \;\;\;\;\frac{\frac{e^{\log \left({1}^{3} - \log \left(e^{{\left(\cos x\right)}^{3}}\right)\right)}}{\cos x \cdot \left(\cos x + 1\right) + 1 \cdot 1}}{\sin x}\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{24} \cdot {x}^{3} + \left(\frac{1}{240} \cdot {x}^{5} + \frac{1}{2} \cdot x\right)\\ \end{array}\]

Reproduce

herbie shell --seed 2020161 
(FPCore (x)
  :name "tanhf (example 3.4)"
  :precision binary64
  :herbie-expected 2

  :herbie-target
  (tan (/ x 2.0))

  (/ (- 1.0 (cos x)) (sin x)))