Hi,
The following creates an equation slightly too long for the equation number to
fit on the same line (on a setup with A4 as the default page size).
In LaTeX and XeLaTeX the equation number appears flush right on the next line,
but in LuaLaTeX it appears flush left.
I'm not a member of this list, so if you need further info please contact me
directly.
Bruno Voisin
\documentclass[12pt]{article}
%
\setlength{\oddsidemargin}{0pt}
\setlength{\evensidemargin}{\oddsidemargin}
\setlength{\textwidth}{\paperwidth}
\addtolength{\textwidth}{-2in}
%
\begin{document}
\begin{equation}
\int_0^y
\sqrt{y^2-t^2}
\cos\left(a\sqrt{y^2-t^2}\right)
\cos(bt)\,\mathrm{d}t =
\frac{\pi}{2}y^2
\left[
\frac{J_1\left(y\sqrt{a^2+b^2}\right)}
{y\sqrt{a^2+b^2}}-
\frac{a^2}{a^2+b^2}
J_2\left(y\sqrt{a^2+b^2}\right)
\right].
\end{equation}
\end{document}
