Workaround for align without using amsmath
I guess you mean the copernicus2.cls
provided by the Biogeosciences.
The files can be found on there website.
The class file loads the package txfonts
which must be loaded after amsmath
.
The package txfonts
has a mechanism to redefine some internal commands of amsmath
which amsmath
doesn't have.
You can load the package amsmath
as follows to use align
:
\RequirePackage[fleqn]{amsmath}
\mathindent0pt
\documentclass[journal abbreviation]{copernicus2}
\begin{document}
\begin{align}
1+1&=2 \\
2&=2
\end{align}
Test
\[1+1=2\]
\end{document}
EDIT: Set option fleqn
and mathindent=0pt
@Marco, amsmath
does not load amssymb
. The problem is two fold.
copernicus2.cls
load txfonts.sty
which define various \XintY
macros which amsmath
also define. Since amsmath
define these using \newcommand
the OP get an error because they are already defined.
This works
\documentclass[journal abbreviation]{copernicus2}
\let\iint\relax
\let\iiint\relax
\let\iiiint\relax
\let\idotsint\relax
\usepackage{amssymb,amsmath}
\begin{document}
\begin{align}
1+1&=2 \\
2&=2
\end{align}
\end{document}
Though Marcos solution may be better, because the solution above may use a different font for those integral symbols than the Journal intended.