Average Error: 36.1 → 0.4
Time: 59.3s
Precision: 64
Internal Precision: 128
\[\tan \left(x + \varepsilon\right) - \tan x\]
\[\frac{\frac{\sin \varepsilon}{\cos \varepsilon}}{\frac{\left(1 - \tan \varepsilon \cdot \tan x\right) \cdot \cos x}{\cos x + \frac{\sin x}{\frac{\cos x}{\sin x}}}}\]

Error

Bits error versus x

Bits error versus eps

Target

Original36.1
Target14.5
Herbie0.4
\[\frac{\sin \varepsilon}{\cos x \cdot \cos \left(x + \varepsilon\right)}\]

Derivation

  1. Initial program 36.1

    \[\tan \left(x + \varepsilon\right) - \tan x\]
  2. Using strategy rm
  3. Applied tan-quot36.1

    \[\leadsto \tan \left(x + \varepsilon\right) - \color{blue}{\frac{\sin x}{\cos x}}\]
  4. Applied tan-sum21.6

    \[\leadsto \color{blue}{\frac{\tan x + \tan \varepsilon}{1 - \tan x \cdot \tan \varepsilon}} - \frac{\sin x}{\cos x}\]
  5. Applied frac-sub21.7

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

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

    \[\leadsto \frac{\color{blue}{\frac{\sin \varepsilon}{\cos \varepsilon} \cdot \left(\frac{\sin x}{\frac{\cos x}{\sin x}} + \cos x\right)}}{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}\]
  8. Using strategy rm
  9. Applied associate-/l*0.4

    \[\leadsto \color{blue}{\frac{\frac{\sin \varepsilon}{\cos \varepsilon}}{\frac{\left(1 - \tan x \cdot \tan \varepsilon\right) \cdot \cos x}{\frac{\sin x}{\frac{\cos x}{\sin x}} + \cos x}}}\]
  10. Final simplification0.4

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

Reproduce

herbie shell --seed 2019091 
(FPCore (x eps)
  :name "2tan (problem 3.3.2)"

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

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