\[\sqrt{\frac{1}{2} \cdot \left(1 + \frac{1}{\sqrt{1 + {\left(\frac{2 \cdot \ell}{Om}\right)}^{2} \cdot \left({\sin kx}^{2} + {\sin ky}^{2}\right)}}\right)}\]
\sqrt{\frac{1}{2} \cdot \left(1 + \frac{1}{\sqrt{1 + {\left(\frac{2 \cdot \ell}{Om}\right)}^{2} \cdot \left({\sin kx}^{2} + {\sin ky}^{2}\right)}}\right)}
(FPCore (l Om kx ky)
 :precision binary64
 (sqrt
  (*
   (/ 1.0 2.0)
   (+
    1.0
    (/
     1.0
     (sqrt
      (+
       1.0
       (*
        (pow (/ (* 2.0 l) Om) 2.0)
        (+ (pow (sin kx) 2.0) (pow (sin ky) 2.0))))))))))
double code(double l, double Om, double kx, double ky) {
	return sqrt((1.0 / 2.0) * (1.0 + (1.0 / sqrt(1.0 + (pow(((2.0 * l) / Om), 2.0) * (pow(sin(kx), 2.0) + pow(sin(ky), 2.0)))))));
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2021060 
(FPCore (l Om kx ky)
  :name "Toniolo and Linder, Equation (3a)"
  :precision binary64
  (sqrt (* (/ 1.0 2.0) (+ 1.0 (/ 1.0 (sqrt (+ 1.0 (* (pow (/ (* 2.0 l) Om) 2.0) (+ (pow (sin kx) 2.0) (pow (sin ky) 2.0))))))))))

Backtrace

Failed to produce proof for (*.f64 (pow.f64 (/.f64 (sqrt.f64 l) (/.f64 1 2)) 2) (+.f64 (pow.f64 (sin.f64 kx) 2) (pow.f64 (sin.f64 ky) 2))) to (*.f64 (+.f64 (pow.f64 (sin.f64 ky) 2) (pow.f64 (sin.f64 kx) 2)) (*.f64 l (*.f64 2 2)))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
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