Average Error: 37.2 → 0.2
Time: 5.6s
Precision: binary64
\[\sin \left(x + \varepsilon\right) - \sin x\]
\[\cos x \cdot \sin \varepsilon + \left(-\sin x \cdot \sin \varepsilon\right) \cdot \tan \left(\frac{\varepsilon}{2}\right)\]

Error

Bits error versus x

Bits error versus eps

Target

Original37.2
Target15.1
Herbie0.2
\[2 \cdot \left(\cos \left(x + \frac{\varepsilon}{2}\right) \cdot \sin \left(\frac{\varepsilon}{2}\right)\right)\]

Derivation

  1. Initial program 37.2

    \[\sin \left(x + \varepsilon\right) - \sin x\]
  2. Using strategy rm
  3. Applied sin-sum21.9

    \[\leadsto \color{blue}{\left(\sin x \cdot \cos \varepsilon + \cos x \cdot \sin \varepsilon\right)} - \sin x\]
  4. Taylor expanded around inf 21.9

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

    \[\leadsto \color{blue}{\sin x \cdot \left(\cos \varepsilon - 1\right) + \cos x \cdot \sin \varepsilon}\]
  6. Using strategy rm
  7. Applied flip--0.5

    \[\leadsto \sin x \cdot \color{blue}{\frac{\cos \varepsilon \cdot \cos \varepsilon - 1 \cdot 1}{\cos \varepsilon + 1}} + \cos x \cdot \sin \varepsilon\]
  8. Simplified0.5

    \[\leadsto \sin x \cdot \frac{\color{blue}{\cos \varepsilon \cdot \cos \varepsilon - 1}}{\cos \varepsilon + 1} + \cos x \cdot \sin \varepsilon\]
  9. Using strategy rm
  10. Applied sub-1-cos0.4

    \[\leadsto \sin x \cdot \frac{\color{blue}{-\sin \varepsilon \cdot \sin \varepsilon}}{\cos \varepsilon + 1} + \cos x \cdot \sin \varepsilon\]
  11. Applied distribute-frac-neg0.4

    \[\leadsto \sin x \cdot \color{blue}{\left(-\frac{\sin \varepsilon \cdot \sin \varepsilon}{\cos \varepsilon + 1}\right)} + \cos x \cdot \sin \varepsilon\]
  12. Applied distribute-rgt-neg-out0.4

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

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

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

Reproduce

herbie shell --seed 2020161 
(FPCore (x eps)
  :name "2sin (example 3.3)"
  :precision binary64

  :herbie-target
  (* 2.0 (* (cos (+ x (/ eps 2.0))) (sin (/ eps 2.0))))

  (- (sin (+ x eps)) (sin x)))