The problem can be reproduced from your code. However, the LaTeX run shows several errors:
! LaTeX Error: Environment align undefined.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.6 \begin{align}
After this error, TeX tries to recover as best it can.
You need \usepackage{amsmath}
in the document preamble.
Besides, never use $$
in LaTeX, see Why is \[ ... \] preferable to $$ ... $$?
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
\int_V \mu(u,v,w) \,du\,dv\,dw
\end{equation*}
Some text in between.
\begin{align}
\int_V \mu(u,v,w) \,du\,dv\,dw
\end{align}
\end{document}
\int
. Please, make a complete example reproducing the issue, from\documentclass
to\end{document}
$$ ... $$
anyway (and it helps the readers tremendously if differential d's are upright).$\int$
(one pair of dollars) with the display math version that you get with thealign
environment?