\begin{eqnarray} math formula 1 \\ math formula 2 \\ . . . \end{eqnarray}

The eqnarray environment is used to display a sequence of equations or
inequalities. It is very much like a three-column array environment,
with consecutive rows separated by `\\` and consecutive items within a
row separated by an &. An equation number is placed on every line
unless that line has a `\nonumber` command.