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

\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 r8127 = lambda1;
        double r8128 = lambda2;
        double r8129 = r8127 - r8128;
        double r8130 = sin(r8129);
        double r8131 = phi2;
        double r8132 = cos(r8131);
        double r8133 = r8130 * r8132;
        double r8134 = phi1;
        double r8135 = cos(r8134);
        double r8136 = sin(r8131);
        double r8137 = r8135 * r8136;
        double r8138 = sin(r8134);
        double r8139 = r8138 * r8132;
        double r8140 = cos(r8129);
        double r8141 = r8139 * r8140;
        double r8142 = r8137 - r8141;
        double r8143 = atan2(r8133, r8142);
        return r8143;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019191 
(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

get-representation: Unknown representation #f		L	C
loop	/data/pavpan/nightlies/herbie/interface2/src/points.rkt	122	4
prepare-points	/data/pavpan/nightlies/herbie/interface2/src/points.rkt	146	0
setup-prog!34	/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt	67	0
run-improve43	/data/pavpan/nightlies/herbie/interface2/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