casesequationsvertical alignment
I want to vertically align one equation against two, similar to the cases environment but without the brace: e.g. similar environment to:
There must be another solution to the alignment solution like Case equation without curly brace – I'd like to label it as a single equation.
You could also use a \hphantom{} to add the appropriate amount of horizontal space:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
f(x) &=
\begin{cases}
x\hphantom{-\sqrt{-}} & \text{if } x\geq 0,\\
-x & \text{if } x <0,
\end{cases}\\
g(x) &=
\begin{cases}
\sqrt{x} & \text{if } x \geq 0,\\
-\sqrt{-x} & \text{if } x < 0.
\end{cases}
\end{align}
\end{document}
The following code updates cases to take an optional argument. The optional argument is used as the left delimiter instead of the traditional (default) \lbrace:
\documentclass{article}
\usepackage{amsmath,etoolbox}
\makeatletter
\renewenvironment{cases}[1][\lbrace]{%
\def\@ldelim{#1}
\matrix@check\cases\env@cases
}{%
\endarray\right.%
}
\patchcmd{\env@cases}{\lbrace}{\@ldelim}{}{}
\makeatother
\begin{document}
\[
f(x) = \begin{cases}
a & \text{if $x < 0$} \\
b & \text{otherwise}
\end{cases}
\]
\[
f(x) = \begin{cases}[\langle]
a & \text{if $x < 0$} \\
b & \text{otherwise}
\end{cases}
\]
\end{document}
It should function as expected, even if nested:
\[
f(x) = \begin{cases}
a & \text{if $x < 0$} \\
b & \begin{cases}[\langle]
{} + c & \text{if $x < 7$} \\
{} + d & \text{otherwise}
\end{cases}
\end{cases}
\]
However, you may be better off using a regular array. It depends on how you nest the content.
Best Answer
There's no need to create a special environment; a simple
arrayenvironment will do the job.To make this a numbered
equationenvironment, simply replace\[and\]with\begin{equation}and\end{equation}, respectively.