\[\sqrt{\left(\left(2 \cdot n\right) \cdot U\right) \cdot \left(\left(t - 2 \cdot \frac{\ell \cdot \ell}{Om}\right) - \left(n \cdot {\left(\frac{\ell}{Om}\right)}^{2}\right) \cdot \left(U - U*\right)\right)}\]
\sqrt{\left(\left(2 \cdot n\right) \cdot U\right) \cdot \left(\left(t - 2 \cdot \frac{\ell \cdot \ell}{Om}\right) - \left(n \cdot {\left(\frac{\ell}{Om}\right)}^{2}\right) \cdot \left(U - U*\right)\right)}
double f(double n, double U, double t, double l, double Om, double U_) {
        double r8096 = 2.0;
        double r8097 = n;
        double r8098 = r8096 * r8097;
        double r8099 = U;
        double r8100 = r8098 * r8099;
        double r8101 = t;
        double r8102 = l;
        double r8103 = r8102 * r8102;
        double r8104 = Om;
        double r8105 = r8103 / r8104;
        double r8106 = r8096 * r8105;
        double r8107 = r8101 - r8106;
        double r8108 = r8102 / r8104;
        double r8109 = pow(r8108, r8096);
        double r8110 = r8097 * r8109;
        double r8111 = U_;
        double r8112 = r8099 - r8111;
        double r8113 = r8110 * r8112;
        double r8114 = r8107 - r8113;
        double r8115 = r8100 * r8114;
        double r8116 = sqrt(r8115);
        return r8116;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019191 
(FPCore (n U t l Om U*)
  :name "Toniolo and Linder, Equation (13)"
  (sqrt (* (* (* 2.0 n) U) (- (- t (* 2.0 (/ (* l l) Om))) (* (* n (pow (/ l Om) 2.0)) (- U U*))))))

Backtrace

get-representation: Unknown representation #fLC
loop/data/pavpan/nightlies/herbie/interface2/src/points.rkt1224
prepare-points/data/pavpan/nightlies/herbie/interface2/src/points.rkt1460
setup-prog!34/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt670
run-improve43/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt3390
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128
run/opt/racket-7.0/share/pkgs/profile-lib/main.rkt392
profile-thunk16/opt/racket-7.0/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128