  The inclination of low-eccentricity orbits is shown to significantly affect
the orbital parameters, in particular, the Keplerian, nodal precession, and
periastron rotation frequencies, which are interpreted in terms of observable
quantities. For the nodal precession and periastron rotation frequencies of
low-eccentricity orbits in a Kerr field, we derive a Taylor expansion in terms
of the Kerr parameter at arbitrary orbital inclinations to the black-hole spin
axis and at arbitrary radial coordinates. The particle radius, energy, and
angular momentum in the marginally stable circular orbits are calculated as
functions of the Kerr parameter $j$ and parameter $s$ in the form of Taylor
expansions in terms of $j$ to within $O[j^6]$. By analyzing our numerical
results, we give compact approximation formulas for the nodal precession
frequency of the marginally stable circular orbits at various $s$ in the entire
range of variation of Kerr parameter.
