\[\cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \cos \left(\lambda_1 - \lambda_2\right)\right) \cdot R\]

\cos^{-1} \left(\sin \phi_1 \cdot \sin \phi_2 + \left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \cos \left(\lambda_1 - \lambda_2\right)\right) \cdot R

double f(double R, double lambda1, double lambda2, double phi1, double phi2) {
        double r18896 = phi1;
        double r18897 = sin(r18896);
        double r18898 = phi2;
        double r18899 = sin(r18898);
        double r18900 = r18897 * r18899;
        double r18901 = cos(r18896);
        double r18902 = cos(r18898);
        double r18903 = r18901 * r18902;
        double r18904 = lambda1;
        double r18905 = lambda2;
        double r18906 = r18904 - r18905;
        double r18907 = cos(r18906);
        double r18908 = r18903 * r18907;
        double r18909 = r18900 + r18908;
        double r18910 = acos(r18909);
        double r18911 = R;
        double r18912 = r18910 * r18911;
        return r18912;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019323 +o rules:numerics
(FPCore (R lambda1 lambda2 phi1 phi2)
  :name "Spherical law of cosines"
  :precision binary64
  (* (acos (+ (* (sin phi1) (sin phi2)) (* (* (cos phi1) (cos phi2)) (cos (- lambda1 lambda2))))) R))

Backtrace

get-representation: Unknown representation real		L	C
(unnamed)	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/core/regimes.rkt	65	3
filter	/opt/racket-7.2/collects/racket/private/list.rkt	256	2
infer-splitpoints	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/core/regimes.rkt	34	0
get-final-combination	/data/pavpan/nightlies/herbie/fix-interface-bugs/src/mainloop.rkt	369	0
(unnamed)	/opt/racket-7.2/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.2/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.2/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.2/collects/racket/private/more-scheme.rkt	261	28