Adding vertical space in a multi-line equation while using IEEEeqnarray

Question

how can I add vertical space between lines in an equation while using IEEEeqnarray?

Answer 1

You can use the optional argument for \\:

\documentclass{IEEEtran}

\begin{document}

\begin{IEEEeqnarray}{c}
a = b\\[5pt]
c=d
\end{IEEEeqnarray}

\end{document}

Answer 2

If you want to change the spacing for all the lines in the current IEEEeqnarray environment you can use:

\documentclass{IEEEtran}

\begin{document}{\setlength{\IEEEnormaljot}{15pt}%
\begin{IEEEeqnarray}{c}
a = b\\
c=d\\
e=f
\end{IEEEeqnarray}
}
\end{document}

Note the additional { which makes the setting local to this group and does not affect other IEEEeqnarray environments. Alternatively you could define your own environment that contains this setting:

\documentclass{IEEEtran}

\newenvironment{MyIEEEeqnarray}[1][c]{%
    \setlength{\IEEEnormaljot}{15pt}%
    \begin{IEEEeqnarray}{#1}%
}{%
    \end{IEEEeqnarray}%
}%

\begin{document}
\begin{MyIEEEeqnarray}[c]
a = b\\
c=d\\
e=f
\end{MyIEEEeqnarray}
\end{document}

Here I made the [c] setting optional.

Answer 3

You can set the \jot length in the \IEEEeqnarraydecl hook:

\documentclass{article}

\usepackage{IEEEtrantools}

\renewcommand*{\IEEEeqnarraydecl}{%
  \setlength{\jot}{2\IEEEnormaljot}% twice the normal value of \jot
}

\begin{document}

\begin{IEEEeqnarray}{RCL}
  a&=&b\\
  x&=&y
\end{IEEEeqnarray}

\end{document}

Alternatively, you can set \jot in the optional argument of the IEEEeqnarray environment. Note that, in both cases, the change of \jot is only local.