\[R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)\]
R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)double f(double R, double lambda1, double lambda2, double phi1, double phi2) {
double r5064779 = R;
double r5064780 = 2.0;
double r5064781 = phi1;
double r5064782 = phi2;
double r5064783 = r5064781 - r5064782;
double r5064784 = r5064783 / r5064780;
double r5064785 = sin(r5064784);
double r5064786 = pow(r5064785, r5064780);
double r5064787 = cos(r5064781);
double r5064788 = cos(r5064782);
double r5064789 = r5064787 * r5064788;
double r5064790 = lambda1;
double r5064791 = lambda2;
double r5064792 = r5064790 - r5064791;
double r5064793 = r5064792 / r5064780;
double r5064794 = sin(r5064793);
double r5064795 = r5064789 * r5064794;
double r5064796 = r5064795 * r5064794;
double r5064797 = r5064786 + r5064796;
double r5064798 = sqrt(r5064797);
double r5064799 = 1.0;
double r5064800 = r5064799 - r5064797;
double r5064801 = sqrt(r5064800);
double r5064802 = atan2(r5064798, r5064801);
double r5064803 = r5064780 * r5064802;
double r5064804 = r5064779 * r5064803;
return r5064804;
}