where is an arbitrary small positive constant. If the series on the right-hand side of (11.6.1) is truncated after terms, then the remainder term is . If is real, is positive, and , then is of the same sign and numerically less than the first neglected term.
and for fixed
and for higher coefficients see Dingle (1973, p. 203).
and for an estimate of the relative error in this approximation see Watson (1944, p. 336).