\[\tan^{-1}_* \frac{\sin \left(\lambda_1 - \lambda_2\right) \cdot \cos \phi_2}{\cos \phi_1 \cdot \sin \phi_2 - \left(\sin \phi_1 \cdot \cos \phi_2\right) \cdot \cos \left(\lambda_1 - \lambda_2\right)}\]

\tan^{-1}_* \frac{\sin \left(\lambda_1 - \lambda_2\right) \cdot \cos \phi_2}{\cos \phi_1 \cdot \sin \phi_2 - \left(\sin \phi_1 \cdot \cos \phi_2\right) \cdot \cos \left(\lambda_1 - \lambda_2\right)}

double f(double lambda1, double lambda2, double phi1, double phi2) {
        double r6869992 = lambda1;
        double r6869993 = lambda2;
        double r6869994 = r6869992 - r6869993;
        double r6869995 = sin(r6869994);
        double r6869996 = phi2;
        double r6869997 = cos(r6869996);
        double r6869998 = r6869995 * r6869997;
        double r6869999 = phi1;
        double r6870000 = cos(r6869999);
        double r6870001 = sin(r6869996);
        double r6870002 = r6870000 * r6870001;
        double r6870003 = sin(r6869999);
        double r6870004 = r6870003 * r6869997;
        double r6870005 = cos(r6869994);
        double r6870006 = r6870004 * r6870005;
        double r6870007 = r6870002 - r6870006;
        double r6870008 = atan2(r6869998, r6870007);
        return r6870008;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019173 
(FPCore (lambda1 lambda2 phi1 phi2)
  :name "Bearing on a great circle"
  (atan2 (* (sin (- lambda1 lambda2)) (cos phi2)) (- (* (cos phi1) (sin phi2)) (* (* (sin phi1) (cos phi2)) (cos (- lambda1 lambda2))))))

Backtrace

hash-ref: no value found for key key: #<enode 514(514)>		L	C
for-loop	/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt	197	2
extractor-extract	/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt	196	0
for-loop	/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt	35	2
(unnamed)	/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt	26	0
simplify!	/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt	217	0
run-iter!	/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt	320	0
for-loop	/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt	354	4
run-improve43	/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt	339	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28