\[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right)\]
\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right)
(FPCore (a1 a2 th)
 :precision binary64
 (+
  (* (/ (cos th) (sqrt 2.0)) (* a1 a1))
  (* (/ (cos th) (sqrt 2.0)) (* a2 a2))))
double code(double a1, double a2, double th) {
	return ((cos(th) / sqrt(2.0)) * (a1 * a1)) + ((cos(th) / sqrt(2.0)) * (a2 * a2));
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2021060 
(FPCore (a1 a2 th)
  :name "Migdal et al, Equation (64)"
  :precision binary64
  (+ (* (/ (cos th) (sqrt 2.0)) (* a1 a1)) (* (/ (cos th) (sqrt 2.0)) (* a2 a2))))

Backtrace

Failed to produce proof for (/.f64 (/.f64 (*.f64 (cbrt.f64 (+.f64 (*.f64 a2 a2) (*.f64 a1 a1))) (cbrt.f64 (+.f64 (*.f64 a2 a2) (*.f64 a1 a1)))) (*.f64 (cbrt.f64 (sqrt.f64 (sqrt.f64 2))) (cbrt.f64 (sqrt.f64 (sqrt.f64 2))))) (*.f64 (cbrt.f64 (sqrt.f64 (sqrt.f64 2))) (cbrt.f64 (sqrt.f64 (sqrt.f64 2))))) to (/.f64 (*.f64 (cbrt.f64 (+.f64 (*.f64 a1 a1) (*.f64 a2 a2))) (cbrt.f64 (+.f64 (*.f64 a1 a1) (*.f64 a2 a2)))) (*.f64 (sqrt.f64 (sqrt.f64 2)) (cbrt.f64 (sqrt.f64 (sqrt.f64 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