\[R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)\]
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 r8491267 = R;
double r8491268 = 2.0;
double r8491269 = phi1;
double r8491270 = phi2;
double r8491271 = r8491269 - r8491270;
double r8491272 = r8491271 / r8491268;
double r8491273 = sin(r8491272);
double r8491274 = pow(r8491273, r8491268);
double r8491275 = cos(r8491269);
double r8491276 = cos(r8491270);
double r8491277 = r8491275 * r8491276;
double r8491278 = lambda1;
double r8491279 = lambda2;
double r8491280 = r8491278 - r8491279;
double r8491281 = r8491280 / r8491268;
double r8491282 = sin(r8491281);
double r8491283 = r8491277 * r8491282;
double r8491284 = r8491283 * r8491282;
double r8491285 = r8491274 + r8491284;
double r8491286 = sqrt(r8491285);
double r8491287 = 1.0;
double r8491288 = r8491287 - r8491285;
double r8491289 = sqrt(r8491288);
double r8491290 = atan2(r8491286, r8491289);
double r8491291 = r8491268 * r8491290;
double r8491292 = r8491267 * r8491291;
return r8491292;
}