[Tex/LaTex] Cases environment compresses fractions

cases

what should I do to stop the cases environment compressing the first line of the following?

\begin{equation}
\alpha_{mn} = \begin{cases} \frac{16\mu^2}{mn\pi^2\left[\pi^2(m^2/a^2 + n^2/b^2) - \mu^2\right]} &\mbox{for } m \mbox{ and } n \mbox{ odd;} 
\\ 0 &\mbox{for } m \mbox{ or } n \mbox{ even;} \end{cases} \\[1ex]
\end{equation}

I'm not sure to do tex on this site, but if anyone tries it they see the first case is compressed because it's a fraction.

Best Answer

The package mathtools (that also loads amsmath) provides dcases and dcases*:

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{equation}
\alpha_{mn} =
\begin{dcases*}
\frac{16\mu^2}{mn\pi^2[\pi^2(m^2/a^2 + n^2/b^2) - \mu^2]} &
  for $m$ and $n$ odd;\\
0\vphantom{\frac{0}{0}} & for $m$ or $n$ even;
\end{dcases*}
\end{equation}
\end{document}

enter image description here

The difference between cases and dcases is that display style is used in the latter, but not in the former. The dcases* form sets the second part in text mode, making it more convenient to type textual conditions.

The \vphantom{\frac{0}{0}} is an adjustment to make the construction more balanced. Note that you don't need \left and \right in the denominator, which would make the brackets too big.

Related Solutions

[Tex/LaTex] Aligning equations in a cases environment

I think that you want to use \left\{...\right. around your equation. To be able to align your equations inside these you can use the split environment from the amsmath package.

EDIT

In the comments both above and below the consensus is that the aligned environment is superior to split in this situation. Perhaps I am missing it but I can't see the difference in this example, however, as people more knowledgeable than I are advocating using the aligned environment there must be cases where it does matter.

Here is a comparison of the two environments for this example:

enter image description here

This produces:

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator\vol{\text{vol}}
\begin{document}
\[\left\{
  \begin{aligned}
    \pi_n  (i) &= {n^2}/{\vol(G_n)} \cr
    \pi_n (j) &=  {n}/{\vol(G_n)} \cr
    q^{(n)}_{ij} &= {1}/{n^2 } \cr
    q^{(n)}_{ji} &= {1}/{n}
  \end{aligned}\right.\tag{\textbf{aligned}}
\]

\[\left\{
  \begin{split}
    \pi_n  (i) &= {n^2}/{\vol(G_n)} \cr
    \pi_n (j) &=  {n}/{\vol(G_n)} \cr
    q^{(n)}_{ij} &= {1}/{n^2 } \cr
    q^{(n)}_{ji} &= {1}/{n}
  \end{split}\right.\tag{\textbf{split}}
\]

\end{document}

Compress cases environment horizontally

You can move the condition to a new line:

\documentclass{article}
\usepackage{mathtools}
\usepackage{lipsum}

\begin{document}

\lipsum[66]
\begin{equation}
G(x,u) = \begin{cases}
-\dfrac{\cosh(\pi-x-u)+\cosh(\pi+x+u)-2\cosh(\pi+x-u)}{4\sinh\pi} & \\
                     & \makebox[0pt][r]{for $0 \le x \le u \le\pi$} \\[2ex]
-\dfrac{\cosh(\pi-x-u)+\cosh(\pi+x+u)-2\cosh(\pi-x+u)}{4\sinh\pi} & \\
                     & \makebox[0pt][r]{$0\le u\le x\le\pi$}
\end{cases}
\end{equation}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Aligning equations in a cases environment

Compress cases environment horizontally

Related Question