\[R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)\]
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 r2507598 = R;
double r2507599 = 2.0;
double r2507600 = phi1;
double r2507601 = phi2;
double r2507602 = r2507600 - r2507601;
double r2507603 = r2507602 / r2507599;
double r2507604 = sin(r2507603);
double r2507605 = pow(r2507604, r2507599);
double r2507606 = cos(r2507600);
double r2507607 = cos(r2507601);
double r2507608 = r2507606 * r2507607;
double r2507609 = lambda1;
double r2507610 = lambda2;
double r2507611 = r2507609 - r2507610;
double r2507612 = r2507611 / r2507599;
double r2507613 = sin(r2507612);
double r2507614 = r2507608 * r2507613;
double r2507615 = r2507614 * r2507613;
double r2507616 = r2507605 + r2507615;
double r2507617 = sqrt(r2507616);
double r2507618 = 1.0;
double r2507619 = r2507618 - r2507616;
double r2507620 = sqrt(r2507619);
double r2507621 = atan2(r2507617, r2507620);
double r2507622 = r2507599 * r2507621;
double r2507623 = r2507598 * r2507622;
return r2507623;
}