Average Error: 59.9 → 0.0
Time: 44.8s
Precision: 64
\[-0.026 \lt x \land x \lt 0.026\]
\[\frac{1}{x} - \frac{1}{\tan x}\]
↓
\[\frac{x}{\frac{\frac{1}{3} - \frac{1}{45} \cdot \left(x \cdot x\right)}{\frac{1}{9} - \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right) \cdot \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right)}} + \frac{2}{945} \cdot {x}^{5}\]
\frac{1}{x} - \frac{1}{\tan x}
↓
\frac{x}{\frac{\frac{1}{3} - \frac{1}{45} \cdot \left(x \cdot x\right)}{\frac{1}{9} - \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right) \cdot \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right)}} + \frac{2}{945} \cdot {x}^{5}
double f(double x) {
        double r6240146 = 1.0;
        double r6240147 = x;
        double r6240148 = r6240146 / r6240147;
        double r6240149 = tan(r6240147);
        double r6240150 = r6240146 / r6240149;
        double r6240151 = r6240148 - r6240150;
        return r6240151;
}
↓
double f(double x) {
        double r6240152 = x;
        double r6240153 = 0.3333333333333333;
        double r6240154 = 0.022222222222222223;
        double r6240155 = r6240152 * r6240152;
        double r6240156 = r6240154 * r6240155;
        double r6240157 = r6240153 - r6240156;
        double r6240158 = 0.1111111111111111;
        double r6240159 = r6240156 * r6240156;
        double r6240160 = r6240158 - r6240159;
        double r6240161 = r6240157 / r6240160;
        double r6240162 = r6240152 / r6240161;
        double r6240163 = 0.0021164021164021165;
        double r6240164 = 5.0;
        double r6240165 = pow(r6240152, r6240164);
        double r6240166 = r6240163 * r6240165;
        double r6240167 = r6240162 + r6240166;
        return r6240167;
}

Error

Bits error versus x

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original59.9
Target0.1
Herbie0.0
\[\begin{array}{l} \mathbf{if}\;\left|x\right| \lt 0.026:\\ \;\;\;\;\frac{x}{3} \cdot \left(1 + \frac{x \cdot x}{15}\right)\\ \mathbf{else}:\\ \;\;\;\;\frac{1}{x} - \frac{1}{\tan x}\\ \end{array}\]

Derivation

  1. Initial program 59.9

    \[\frac{1}{x} - \frac{1}{\tan x}\]

  2. Taylor expanded around 0 0.3

    \[\leadsto \color{blue}{\frac{1}{3} \cdot x + \left(\frac{1}{45} \cdot {x}^{3} + \frac{2}{945} \cdot {x}^{5}\right)}\]

  3. Simplified0.3

    \[\leadsto \color{blue}{x \cdot \left(\frac{1}{3} + \frac{1}{45} \cdot \left(x \cdot x\right)\right) + {x}^{5} \cdot \frac{2}{945}}\]
  4. Using strategy rm

  5. Applied flip-+0.3

    \[\leadsto x \cdot \color{blue}{\frac{\frac{1}{3} \cdot \frac{1}{3} - \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right) \cdot \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right)}{\frac{1}{3} - \frac{1}{45} \cdot \left(x \cdot x\right)}} + {x}^{5} \cdot \frac{2}{945}\]

  6. Applied associate-*r/0.3

    \[\leadsto \color{blue}{\frac{x \cdot \left(\frac{1}{3} \cdot \frac{1}{3} - \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right) \cdot \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right)\right)}{\frac{1}{3} - \frac{1}{45} \cdot \left(x \cdot x\right)}} + {x}^{5} \cdot \frac{2}{945}\]
  7. Using strategy rm

  8. Applied associate-/l*0.0

    \[\leadsto \color{blue}{\frac{x}{\frac{\frac{1}{3} - \frac{1}{45} \cdot \left(x \cdot x\right)}{\frac{1}{3} \cdot \frac{1}{3} - \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right) \cdot \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right)}}} + {x}^{5} \cdot \frac{2}{945}\]

  9. Final simplification0.0

    \[\leadsto \frac{x}{\frac{\frac{1}{3} - \frac{1}{45} \cdot \left(x \cdot x\right)}{\frac{1}{9} - \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right) \cdot \left(\frac{1}{45} \cdot \left(x \cdot x\right)\right)}} + \frac{2}{945} \cdot {x}^{5}\]

Reproduce

herbie shell --seed 2019124 
(FPCore (x)
  :name "invcot (example 3.9)"
  :pre (and (< -0.026 x) (< x 0.026))

  :herbie-target
  (if (< (fabs x) 0.026) (* (/ x 3) (+ 1 (/ (* x x) 15))) (- (/ 1 x) (/ 1 (tan x))))

  (- (/ 1 x) (/ 1 (tan x))))