double f(double lambda1, double lambda2, double phi1, double phi2) {
double r2789701 = lambda1;
double r2789702 = lambda2;
double r2789703 = r2789701 - r2789702;
double r2789704 = sin(r2789703);
double r2789705 = phi2;
double r2789706 = cos(r2789705);
double r2789707 = r2789704 * r2789706;
double r2789708 = phi1;
double r2789709 = cos(r2789708);
double r2789710 = sin(r2789705);
double r2789711 = r2789709 * r2789710;
double r2789712 = sin(r2789708);
double r2789713 = r2789712 * r2789706;
double r2789714 = cos(r2789703);
double r2789715 = r2789713 * r2789714;
double r2789716 = r2789711 - r2789715;
double r2789717 = atan2(r2789707, r2789716);
return r2789717;
}