\[R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)\]
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 r2185285 = R;
double r2185286 = 2.0;
double r2185287 = phi1;
double r2185288 = phi2;
double r2185289 = r2185287 - r2185288;
double r2185290 = r2185289 / r2185286;
double r2185291 = sin(r2185290);
double r2185292 = pow(r2185291, r2185286);
double r2185293 = cos(r2185287);
double r2185294 = cos(r2185288);
double r2185295 = r2185293 * r2185294;
double r2185296 = lambda1;
double r2185297 = lambda2;
double r2185298 = r2185296 - r2185297;
double r2185299 = r2185298 / r2185286;
double r2185300 = sin(r2185299);
double r2185301 = r2185295 * r2185300;
double r2185302 = r2185301 * r2185300;
double r2185303 = r2185292 + r2185302;
double r2185304 = sqrt(r2185303);
double r2185305 = 1.0;
double r2185306 = r2185305 - r2185303;
double r2185307 = sqrt(r2185306);
double r2185308 = atan2(r2185304, r2185307);
double r2185309 = r2185286 * r2185308;
double r2185310 = r2185285 * r2185309;
return r2185310;
}