\[\cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - 1}\right)\]
\cos^{-1} \left(\frac{1 - 5 \cdot \left(v \cdot v\right)}{v \cdot v - 1}\right)
(FPCore (v)
 :precision binary64
 (acos (/ (- 1.0 (* 5.0 (* v v))) (- (* v v) 1.0))))
double code(double v) {
	return acos((1.0 - (5.0 * (v * v))) / ((v * v) - 1.0));
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2021060 
(FPCore (v)
  :name "Falkner and Boettcher, Appendix B, 1"
  :precision binary64
  (acos (/ (- 1.0 (* 5.0 (* v v))) (- (* v v) 1.0))))

Backtrace

Failed to produce proof for (*.f64 (sqrt.f64 (sqrt.f64 (acos.f64 (/.f64 (/.f64 (-.f64 1 (*.f64 5 (*.f64 v v))) (+.f64 v -1)) (+.f64 1 v))))) (sqrt.f64 (sqrt.f64 (acos.f64 (/.f64 (-.f64 1 (*.f64 5 (*.f64 v v))) (+.f64 (*.f64 v v) -1)))))) to (sqrt.f64 (acos.f64 (/.f64 (-.f64 1 (*.f64 5 (*.f64 v v))) (+.f64 (*.f64 v v) -1))))LC
for-loop/data/pavpan/nightlies/herbie/egg-generate-proof/src/core/simplify.rkt1678
(unnamed)/data/pavpan/nightlies/herbie/egg-generate-proof/src/core/simplify.rkt1496
egraph-add-exprs/data/pavpan/nightlies/herbie/egg-generate-proof/egg-herbie/main.rkt1540
with-egraph/data/pavpan/nightlies/herbie/egg-generate-proof/egg-herbie/main.rkt740
(unnamed)/data/pavpan/nightlies/herbie/egg-generate-proof/src/core/simplify.rkt790
simplify!/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt2360
run-iter!/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt3600
for-loop/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt3912
run-improve/data/pavpan/nightlies/herbie/egg-generate-proof/src/mainloop.rkt3770
(unnamed)/data/pavpan/nightlies/herbie/egg-generate-proof/src/sandbox.rkt546
run/opt/racket-7.9/share/pkgs/profile-lib/main.rkt392
profile-thunk/opt/racket-7.9/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.9/collects/racket/engine.rkt4224