Average Error: 0.6 → 0.9
Time: 5.7s
Precision: 64
\[\cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - 1}\right)\]
↓
\[\cos^{-1} \left(\frac{\frac{1 - 5 \cdot \left(v \cdot v\right)}{v + \sqrt{1}}}{v - \sqrt{1}}\right)\]
\cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - 1}\right)
↓
\cos^{-1} \left(\frac{\frac{1 - 5 \cdot \left(v \cdot v\right)}{v + \sqrt{1}}}{v - \sqrt{1}}\right)
double code(double v) {
	return acos(((1.0 - (5.0 * (v * v))) / ((v * v) - 1.0)));
}
↓
double code(double v) {
	return acos((((1.0 - (5.0 * (v * v))) / (v + sqrt(1.0))) / (v - sqrt(1.0))));
}

Error

Bits error versus v

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Derivation

  1. Initial program 0.6

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

  3. Applied add-sqr-sqrt0.6

    \[\leadsto \cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - \color{blue}{\sqrt{1} \cdot \sqrt{1}}}\right)\]

  4. Applied difference-of-squares0.9

    \[\leadsto \cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{\color{blue}{\left(v + \sqrt{1}\right) \cdot \left(v - \sqrt{1}\right)}}\right)\]

  5. Applied associate-/r*0.9

    \[\leadsto \cos^{-1} \color{blue}{\left(\frac{\frac{1 - 5 \cdot \left(v \cdot v\right)}{v + \sqrt{1}}}{v - \sqrt{1}}\right)}\]

  6. Final simplification0.9

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

Reproduce

herbie shell --seed 2020058 
(FPCore (v)
  :name "Falkner and Boettcher, Appendix B, 1"
  :precision binary64
  (acos (/ (- 1 (* 5 (* v v))) (- (* v v) 1))))