private void ZetaInv(double taup, double lam, out double u, out double v)
{
double
psi = Asinh(taup),
scal = 1 / Hypot(1, taup);
if (ZetaInv0(psi, lam, out u, out v))
{
return;
}
var stol2 = tol2_ / Sq(Max(psi, 1));
// min iterations = 2, max iterations = 6; mean = 4.0
for (int i = 0, trip = 0; i < numit_ || GEOGRAPHICLIB_PANIC; ++i)
{
_Eu.Sncndn(u, out var snu, out var cnu, out var dnu);
_Ev.Sncndn(v, out var snv, out var cnv, out var dnv);
Zeta(u, snu, cnu, dnu, v, snv, cnv, dnv, out var tau1, out var lam1);
DwdZeta(u, snu, cnu, dnu, v, snv, cnv, dnv, out var du1, out var dv1);
tau1 -= taup;
lam1 -= lam;
tau1 *= scal;
double
delu = tau1 * du1 - lam1 * dv1,
delv = tau1 * dv1 + lam1 * du1;
u -= delu;
v -= delv;
if (trip != 0)
{
break;
}
var delw2 = Sq(delu) + Sq(delv);
if (!(delw2 >= stol2))
{
++trip;
}
}
}
