\[\left(\left(-2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \sqrt{1 + {\left(\frac{U}{\left(2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)}\right)}^{2}}\]

\left(\left(-2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)\right) \cdot \sqrt{1 + {\left(\frac{U}{\left(2 \cdot J\right) \cdot \cos \left(\frac{K}{2}\right)}\right)}^{2}}

double f(double J, double K, double U) {
        double r82670 = -2.0;
        double r82671 = J;
        double r82672 = r82670 * r82671;
        double r82673 = K;
        double r82674 = 2.0;
        double r82675 = r82673 / r82674;
        double r82676 = cos(r82675);
        double r82677 = r82672 * r82676;
        double r82678 = 1.0;
        double r82679 = U;
        double r82680 = r82674 * r82671;
        double r82681 = r82680 * r82676;
        double r82682 = r82679 / r82681;
        double r82683 = pow(r82682, r82674);
        double r82684 = r82678 + r82683;
        double r82685 = sqrt(r82684);
        double r82686 = r82677 * r82685;
        return r82686;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019323 
(FPCore (J K U)
  :name "Maksimov and Kolovsky, Equation (3)"
  :precision binary64
  (* (* (* -2 J) (cos (/ K 2))) (sqrt (+ 1 (pow (/ U (* (* 2 J) (cos (/ K 2)))) 2)))))

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