\[\frac{2}{\left(\left(\frac{{t}^{3}}{\ell \cdot \ell} \cdot \sin k\right) \cdot \tan k\right) \cdot \left(\left(1 + {\left(\frac{k}{t}\right)}^{2}\right) - 1\right)}\]

\frac{2}{\left(\left(\frac{{t}^{3}}{\ell \cdot \ell} \cdot \sin k\right) \cdot \tan k\right) \cdot \left(\left(1 + {\left(\frac{k}{t}\right)}^{2}\right) - 1\right)}

double f(double t, double l, double k) {
        double r77604666 = 2.0;
        double r77604667 = t;
        double r77604668 = 3.0;
        double r77604669 = pow(r77604667, r77604668);
        double r77604670 = l;
        double r77604671 = r77604670 * r77604670;
        double r77604672 = r77604669 / r77604671;
        double r77604673 = k;
        double r77604674 = sin(r77604673);
        double r77604675 = r77604672 * r77604674;
        double r77604676 = tan(r77604673);
        double r77604677 = r77604675 * r77604676;
        double r77604678 = 1.0;
        double r77604679 = r77604673 / r77604667;
        double r77604680 = pow(r77604679, r77604666);
        double r77604681 = r77604678 + r77604680;
        double r77604682 = r77604681 - r77604678;
        double r77604683 = r77604677 * r77604682;
        double r77604684 = r77604666 / r77604683;
        return r77604684;
}

Reproduce

herbie shell --seed 2019128 
(FPCore (t l k)
  :name "Toniolo and Linder, Equation (10-)"
  (/ 2 (* (* (* (/ (pow t 3) (* l l)) (sin k)) (tan k)) (- (+ 1 (pow (/ k t) 2)) 1))))

Timeout in 10.0m

Reproduce