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

\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 r4647804 = 2.0;
        double r4647805 = t;
        double r4647806 = 3.0;
        double r4647807 = pow(r4647805, r4647806);
        double r4647808 = l;
        double r4647809 = r4647808 * r4647808;
        double r4647810 = r4647807 / r4647809;
        double r4647811 = k;
        double r4647812 = sin(r4647811);
        double r4647813 = r4647810 * r4647812;
        double r4647814 = tan(r4647811);
        double r4647815 = r4647813 * r4647814;
        double r4647816 = 1.0;
        double r4647817 = r4647811 / r4647805;
        double r4647818 = pow(r4647817, r4647804);
        double r4647819 = r4647816 + r4647818;
        double r4647820 = r4647819 - r4647816;
        double r4647821 = r4647815 * r4647820;
        double r4647822 = r4647804 / r4647821;
        return r4647822;
}

Reproduce

herbie shell --seed 2019143 
(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