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

\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 r41763770 = 2.0;
        double r41763771 = t;
        double r41763772 = 3.0;
        double r41763773 = pow(r41763771, r41763772);
        double r41763774 = l;
        double r41763775 = r41763774 * r41763774;
        double r41763776 = r41763773 / r41763775;
        double r41763777 = k;
        double r41763778 = sin(r41763777);
        double r41763779 = r41763776 * r41763778;
        double r41763780 = tan(r41763777);
        double r41763781 = r41763779 * r41763780;
        double r41763782 = 1.0;
        double r41763783 = r41763777 / r41763771;
        double r41763784 = pow(r41763783, r41763770);
        double r41763785 = r41763782 + r41763784;
        double r41763786 = r41763785 - r41763782;
        double r41763787 = r41763781 * r41763786;
        double r41763788 = r41763770 / r41763787;
        return r41763788;
}

Reproduce

herbie shell --seed 2019134 
(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