Average Error: 30.8 → 0.3
Time: 31.5s
Precision: 64
\[\frac{1 - \cos x}{x \cdot x}\]
\[\frac{\frac{\sin x}{x} \cdot \frac{\sin x}{x}}{e^{\log \left(1 + \cos x\right)}}\]
double f(double x) {
        double r1884235 = 1.0;
        double r1884236 = x;
        double r1884237 = cos(r1884236);
        double r1884238 = r1884235 - r1884237;
        double r1884239 = r1884236 * r1884236;
        double r1884240 = r1884238 / r1884239;
        return r1884240;
}

double f(double x) {
        double r1884241 = x;
        double r1884242 = sin(r1884241);
        double r1884243 = r1884242 / r1884241;
        double r1884244 = r1884243 * r1884243;
        double r1884245 = 1.0;
        double r1884246 = cos(r1884241);
        double r1884247 = r1884245 + r1884246;
        double r1884248 = log(r1884247);
        double r1884249 = exp(r1884248);
        double r1884250 = r1884244 / r1884249;
        return r1884250;
}

\frac{1 - \cos x}{x \cdot x}
\frac{\frac{\sin x}{x} \cdot \frac{\sin x}{x}}{e^{\log \left(1 + \cos x\right)}}

Error

Bits error versus x

Derivation

  1. Initial program 30.8

    \[\frac{1 - \cos x}{x \cdot x}\]
  2. Using strategy rm
  3. Applied flip--30.9

    \[\leadsto \frac{\color{blue}{\frac{1 \cdot 1 - \cos x \cdot \cos x}{1 + \cos x}}}{x \cdot x}\]
  4. Applied associate-/l/30.9

    \[\leadsto \color{blue}{\frac{1 \cdot 1 - \cos x \cdot \cos x}{\left(x \cdot x\right) \cdot \left(1 + \cos x\right)}}\]
  5. Simplified15.2

    \[\leadsto \frac{\color{blue}{\sin x \cdot \sin x}}{\left(x \cdot x\right) \cdot \left(1 + \cos x\right)}\]
  6. Taylor expanded around -inf 15.2

    \[\leadsto \color{blue}{\frac{{\left(\sin x\right)}^{2}}{{x}^{2} \cdot \left(\cos x + 1\right)}}\]
  7. Simplified0.3

    \[\leadsto \color{blue}{\frac{\frac{\sin x}{x} \cdot \frac{\sin x}{x}}{\cos x + 1}}\]
  8. Using strategy rm
  9. Applied add-exp-log0.3

    \[\leadsto \frac{\frac{\sin x}{x} \cdot \frac{\sin x}{x}}{\color{blue}{e^{\log \left(\cos x + 1\right)}}}\]
  10. Final simplification0.3

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

Reproduce

herbie shell --seed 2019102 
(FPCore (x)
  :name "cos2 (problem 3.4.1)"
  (/ (- 1 (cos x)) (* x x)))