Average Error: 36.8 → 0.4
Time: 6.2s
Precision: binary64
\[\tan \left(x + \varepsilon\right) - \tan x\]
\[\frac{\sin \varepsilon}{\cos \varepsilon + \sin x \cdot \frac{-\sin \varepsilon}{\cos x}} + \frac{\sin x \cdot \frac{\left(\sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right) \cdot \left(\cos x \cdot 2 - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}{\cos x \cdot 2 - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}}}{\cos x \cdot \left(\cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}\]

Error

Bits error versus x

Bits error versus eps

Target

Original36.8
Target14.9
Herbie0.4
\[\frac{\sin \varepsilon}{\cos x \cdot \cos \left(x + \varepsilon\right)}\]

Derivation

  1. Initial program 36.8

    \[\tan \left(x + \varepsilon\right) - \tan x\]
  2. Using strategy rm
  3. Applied tan-sum21.8

    \[\leadsto \color{blue}{\frac{\tan x + \tan \varepsilon}{1 - \tan x \cdot \tan \varepsilon}} - \tan x\]
  4. Taylor expanded around inf 21.9

    \[\leadsto \color{blue}{\left(\frac{\sin \varepsilon}{\left(1 - \frac{\sin x \cdot \sin \varepsilon}{\cos x \cdot \cos \varepsilon}\right) \cdot \cos \varepsilon} + \frac{\sin x}{\cos x \cdot \left(1 - \frac{\sin x \cdot \sin \varepsilon}{\cos x \cdot \cos \varepsilon}\right)}\right) - \frac{\sin x}{\cos x}}\]
  5. Simplified13.2

    \[\leadsto \color{blue}{\frac{\sin \varepsilon}{\cos \varepsilon + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos x}\right)} + \left(\frac{\sin x}{\cos x + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos \varepsilon}\right)} - \frac{\sin x}{\cos x}\right)}\]
  6. Using strategy rm
  7. Applied frac-sub13.2

    \[\leadsto \frac{\sin \varepsilon}{\cos \varepsilon + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos x}\right)} + \color{blue}{\frac{\sin x \cdot \cos x - \left(\cos x + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos \varepsilon}\right)\right) \cdot \sin x}{\left(\cos x + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos \varepsilon}\right)\right) \cdot \cos x}}\]
  8. Simplified13.2

    \[\leadsto \frac{\sin \varepsilon}{\cos \varepsilon + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos x}\right)} + \frac{\color{blue}{\sin x \cdot \left(\cos x - \left(\cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)\right)}}{\left(\cos x + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos \varepsilon}\right)\right) \cdot \cos x}\]
  9. Simplified13.2

    \[\leadsto \frac{\sin \varepsilon}{\cos \varepsilon + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos x}\right)} + \frac{\sin x \cdot \left(\cos x - \left(\cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)\right)}{\color{blue}{\cos x \cdot \left(\cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}}\]
  10. Using strategy rm
  11. Applied flip--13.2

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

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

    \[\leadsto \frac{\sin \varepsilon}{\cos \varepsilon + 1 \cdot \left(\sin x \cdot \frac{-\sin \varepsilon}{\cos x}\right)} + \frac{\sin x \cdot \frac{\left(\sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right) \cdot \left(2 \cdot \cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}{\color{blue}{2 \cdot \cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}}}}{\cos x \cdot \left(\cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}\]
  14. Final simplification0.4

    \[\leadsto \frac{\sin \varepsilon}{\cos \varepsilon + \sin x \cdot \frac{-\sin \varepsilon}{\cos x}} + \frac{\sin x \cdot \frac{\left(\sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right) \cdot \left(\cos x \cdot 2 - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}{\cos x \cdot 2 - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}}}{\cos x \cdot \left(\cos x - \sin x \cdot \frac{\sin \varepsilon}{\cos \varepsilon}\right)}\]

Reproduce

herbie shell --seed 2020182 
(FPCore (x eps)
  :name "2tan (problem 3.3.2)"
  :precision binary64

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

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