Double linespacing inside equation array

Question

I want to make the spacing between lines inside an equation array wider because the equations are very near to each other, how can I achieve this?

Answer 1

With eqnarray and other multi-line display math environment, you can indicate how much extra vertical whitespace should be inserted after \\ by providing an optional argument (yes, \\ is a macro that can take an optional argument) indicating a valid length, e.g., 1ex or [1cm].

The following screenshot shows eqnarray and align environments without any additional vertical spacing between the rows; on the right, the same equations are separated by additional whitespace, in the amount of 1ex. Select the optimal amount of extra whitespace on a case-by-case basis -- there is no single, uniformly optimal amount.

Finally, if you compare the outputs of eqnarray and align, can you tell why one should not use eqnarray and, instead, use align?

\documentclass{article}
\usepackage{amsmath} % for 'align' environment
\begin{document}
%% set up two side-by-side 'minipage' environments
\begin{minipage}[t]{0.5\textwidth}
\begin{eqnarray}
1 &=& \frac{1}{2}+\frac{1}{2}\\
5 &=& \frac{8}{4}+\frac{5}{15}
\end{eqnarray}
\begin{align}
1 &= \frac{1}{2}+\frac{1}{2}\\
5 &= \frac{8}{4}+\frac{5}{15}
\end{align}
\end{minipage}%
\begin{minipage}[t]{0.5\textwidth}
\begin{eqnarray}
1 &=& \frac{1}{2}+\frac{1}{2}\\[1ex]
5 &=& \frac{8}{4}+\frac{5}{15}
\end{eqnarray}
\begin{align}
1 &= \frac{1}{2}+\frac{1}{2}\\[1ex]
5 &= \frac{8}{4}+\frac{5}{15}
\end{align}
\end{minipage}
\end{document}