Average Error: 0.5 → 0.5
Time: 2.2m
Precision: 64
Internal Precision: 128
\[\cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - 1}\right)\]
\[\cos^{-1} \left(\frac{(\left(v \cdot v\right) \cdot -5 + 1)_*}{(v \cdot v + -1)_*}\right)\]

Error

Bits error versus v

Derivation

  1. Initial program 0.5

    \[\cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - 1}\right)\]
  2. Simplified0.5

    \[\leadsto \color{blue}{\cos^{-1} \left(\frac{(-5 \cdot \left(v \cdot v\right) + 1)_*}{v \cdot v - 1}\right)}\]
  3. Using strategy rm
  4. Applied add-sqr-sqrt0.5

    \[\leadsto \cos^{-1} \left(\frac{\color{blue}{\sqrt{(-5 \cdot \left(v \cdot v\right) + 1)_*} \cdot \sqrt{(-5 \cdot \left(v \cdot v\right) + 1)_*}}}{v \cdot v - 1}\right)\]
  5. Applied associate-/l*0.6

    \[\leadsto \cos^{-1} \color{blue}{\left(\frac{\sqrt{(-5 \cdot \left(v \cdot v\right) + 1)_*}}{\frac{v \cdot v - 1}{\sqrt{(-5 \cdot \left(v \cdot v\right) + 1)_*}}}\right)}\]
  6. Taylor expanded around 0 0.5

    \[\leadsto \color{blue}{\cos^{-1} \left(\frac{(-5 \cdot \left({v}^{2}\right) + 1)_*}{{v}^{2} - 1}\right)}\]
  7. Simplified0.5

    \[\leadsto \color{blue}{\cos^{-1} \left(\frac{(\left(v \cdot v\right) \cdot -5 + 1)_*}{(v \cdot v + -1)_*}\right)}\]
  8. Final simplification0.5

    \[\leadsto \cos^{-1} \left(\frac{(\left(v \cdot v\right) \cdot -5 + 1)_*}{(v \cdot v + -1)_*}\right)\]

Reproduce

herbie shell --seed 2019050 +o rules:numerics
(FPCore (v)
  :name "Falkner and Boettcher, Appendix B, 1"
  (acos (/ (- 1 (* 5 (* v v))) (- (* v v) 1))))