R \cdot \sqrt{\left(\left(\lambda_1 - \lambda_2\right) \cdot \cos \left(\frac{\phi_1 + \phi_2}{2}\right)\right) \cdot \left(\left(\lambda_1 - \lambda_2\right) \cdot \cos \left(\frac{\phi_1 + \phi_2}{2}\right)\right) + \left(\phi_1 - \phi_2\right) \cdot \left(\phi_1 - \phi_2\right)}\begin{array}{l}
\mathbf{if}\;\phi_1 \le -9.164522153818591 \cdot 10^{+154}:\\
\;\;\;\;R \cdot \left(\phi_2 - \phi_1\right)\\
\mathbf{else}:\\
\;\;\;\;R \cdot \sqrt{\left(\phi_1 - \phi_2\right) \cdot \left(\phi_1 - \phi_2\right) + \left(\left(\lambda_1 - \lambda_2\right) \cdot \cos \left(\frac{\phi_1 + \phi_2}{2}\right)\right) \cdot \left(\left(\sqrt[3]{\cos \left(\frac{\phi_1 + \phi_2}{2}\right)} \cdot \left(\sqrt[3]{\cos \left(\frac{\phi_1 + \phi_2}{2}\right)} \cdot \sqrt[3]{\log \left(e^{\cos \left(\frac{\phi_1 + \phi_2}{2}\right)}\right)}\right)\right) \cdot \left(\lambda_1 - \lambda_2\right)\right)}\\
\end{array}double f(double R, double lambda1, double lambda2, double phi1, double phi2) {
double r3629403 = R;
double r3629404 = lambda1;
double r3629405 = lambda2;
double r3629406 = r3629404 - r3629405;
double r3629407 = phi1;
double r3629408 = phi2;
double r3629409 = r3629407 + r3629408;
double r3629410 = 2.0;
double r3629411 = r3629409 / r3629410;
double r3629412 = cos(r3629411);
double r3629413 = r3629406 * r3629412;
double r3629414 = r3629413 * r3629413;
double r3629415 = r3629407 - r3629408;
double r3629416 = r3629415 * r3629415;
double r3629417 = r3629414 + r3629416;
double r3629418 = sqrt(r3629417);
double r3629419 = r3629403 * r3629418;
return r3629419;
}
double f(double R, double lambda1, double lambda2, double phi1, double phi2) {
double r3629420 = phi1;
double r3629421 = -9.164522153818591e+154;
bool r3629422 = r3629420 <= r3629421;
double r3629423 = R;
double r3629424 = phi2;
double r3629425 = r3629424 - r3629420;
double r3629426 = r3629423 * r3629425;
double r3629427 = r3629420 - r3629424;
double r3629428 = r3629427 * r3629427;
double r3629429 = lambda1;
double r3629430 = lambda2;
double r3629431 = r3629429 - r3629430;
double r3629432 = r3629420 + r3629424;
double r3629433 = 2.0;
double r3629434 = r3629432 / r3629433;
double r3629435 = cos(r3629434);
double r3629436 = r3629431 * r3629435;
double r3629437 = cbrt(r3629435);
double r3629438 = exp(r3629435);
double r3629439 = log(r3629438);
double r3629440 = cbrt(r3629439);
double r3629441 = r3629437 * r3629440;
double r3629442 = r3629437 * r3629441;
double r3629443 = r3629442 * r3629431;
double r3629444 = r3629436 * r3629443;
double r3629445 = r3629428 + r3629444;
double r3629446 = sqrt(r3629445);
double r3629447 = r3629423 * r3629446;
double r3629448 = r3629422 ? r3629426 : r3629447;
return r3629448;
}



Bits error versus R



Bits error versus lambda1



Bits error versus lambda2



Bits error versus phi1



Bits error versus phi2
Results
if phi1 < -9.164522153818591e+154Initial program 60.8
rmApplied add-exp-log61.5
Applied add-exp-log61.8
Applied prod-exp61.8
Applied add-exp-log61.8
Applied prod-exp61.8
Simplified60.8
Taylor expanded around 0 15.4
if -9.164522153818591e+154 < phi1 Initial program 34.6
rmApplied add-cube-cbrt34.7
rmApplied add-log-exp34.7
Final simplification32.6
herbie shell --seed 2019138
(FPCore (R lambda1 lambda2 phi1 phi2)
:name "Equirectangular approximation to distance on a great circle"
(* R (sqrt (+ (* (* (- lambda1 lambda2) (cos (/ (+ phi1 phi2) 2))) (* (- lambda1 lambda2) (cos (/ (+ phi1 phi2) 2)))) (* (- phi1 phi2) (- phi1 phi2))))))