Average Error: 37.0 → 0.5
Time: 45.6s
Precision: 64
Internal Precision: 128
\[\tan \left(x + \varepsilon\right) - \tan x\]
\[\frac{\sin \varepsilon}{\frac{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}{\frac{\frac{\sin x \cdot \sin x}{\cos x} + \cos x}{\cos \varepsilon}}}\]

Error

Bits error versus x

Bits error versus eps

Target

Original37.0
Target14.8
Herbie0.5
\[\frac{\sin \varepsilon}{\cos x \cdot \cos \left(x + \varepsilon\right)}\]

Derivation

  1. Initial program 37.0

    \[\tan \left(x + \varepsilon\right) - \tan x\]
  2. Using strategy rm
  3. Applied tan-sum22.1

    \[\leadsto \color{blue}{\frac{\tan x + \tan \varepsilon}{1 - \tan x \cdot \tan \varepsilon}} - \tan x\]
  4. Using strategy rm
  5. Applied tan-quot22.2

    \[\leadsto \frac{\tan x + \tan \varepsilon}{1 - \tan x \cdot \tan \varepsilon} - \color{blue}{\frac{\sin x}{\cos x}}\]
  6. Applied frac-sub22.2

    \[\leadsto \color{blue}{\frac{\left(\tan x + \tan \varepsilon\right) \cdot \cos x - \left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \sin x}{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}}\]
  7. Taylor expanded around -inf 0.4

    \[\leadsto \frac{\color{blue}{\frac{{\left(\sin x\right)}^{2} \cdot \sin \varepsilon}{\cos x \cdot \cos \varepsilon} + \frac{\cos x \cdot \sin \varepsilon}{\cos \varepsilon}}}{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}\]
  8. Simplified0.4

    \[\leadsto \frac{\color{blue}{\frac{\sin \varepsilon \cdot \left(\frac{\sin x \cdot \sin x}{\cos x} + \cos x\right)}{\cos \varepsilon}}}{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}\]
  9. Using strategy rm
  10. Applied *-un-lft-identity0.4

    \[\leadsto \frac{\frac{\sin \varepsilon \cdot \left(\frac{\sin x \cdot \sin x}{\cos x} + \cos x\right)}{\color{blue}{1 \cdot \cos \varepsilon}}}{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}\]
  11. Applied times-frac0.5

    \[\leadsto \frac{\color{blue}{\frac{\sin \varepsilon}{1} \cdot \frac{\frac{\sin x \cdot \sin x}{\cos x} + \cos x}{\cos \varepsilon}}}{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}\]
  12. Applied associate-/l*0.5

    \[\leadsto \color{blue}{\frac{\frac{\sin \varepsilon}{1}}{\frac{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}{\frac{\frac{\sin x \cdot \sin x}{\cos x} + \cos x}{\cos \varepsilon}}}}\]
  13. Simplified0.5

    \[\leadsto \frac{\color{blue}{\sin \varepsilon}}{\frac{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}{\frac{\frac{\sin x \cdot \sin x}{\cos x} + \cos x}{\cos \varepsilon}}}\]
  14. Final simplification0.5

    \[\leadsto \frac{\sin \varepsilon}{\frac{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}{\frac{\frac{\sin x \cdot \sin x}{\cos x} + \cos x}{\cos \varepsilon}}}\]

Reproduce

herbie shell --seed 2019068 
(FPCore (x eps)
  :name "2tan (problem 3.3.2)"

  :herbie-target
  (/ (sin eps) (* (cos x) (cos (+ x eps))))

  (- (tan (+ x eps)) (tan x)))