\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.