# How to shorten equation left bracket?

I need to make a table with some equations and the codes as follow:

\documentclass[12pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath,amsfonts,amssymb}
\def\arraystretch{3}
\setlength\tabcolsep{0.5cm}
\begin{document}
\begin{tabular}{|l|l|}
\hline
$|A|>B \Leftrightarrow \left[ \begin{array}{l}A>B\\A<-B\end{array} \right.$&$|A|\geq B \Leftrightarrow \left[ \begin{array}{l}A \geq B\\A\leq -B\end{array} \right.$\\
\hline
$\sqrt{A}>B \Leftrightarrow \left[ \begin{array}{l}\begin{cases}B < 0\\A\geq 0\end{cases} \\\begin{cases}B\geq 0\\A>B^2\end{cases} \end{array} \right.$ & $\sqrt{A}\geq B \Leftrightarrow \left[ \begin{array} {l}\begin{cases}B < 0\\A\geq 0\end{cases} \\\begin{cases}B\geq 0\\A\geq B^2\end{cases} \end{array} \right.$ \\
\hline
\end{tabular}
\end{document}


I want to shorten the left brackets so that they use less spaces. Thanks for help.

The error is in setting \arraystretch to 3, because the setting is inherited also by the nested array environments.

With some visual formatting it's easier.

\documentclass[12pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath,amsfonts,amssymb}
\begin{document}

\begin{tabular}{|l|l|}
\hline
&\\[-.5\normalbaselineskip]
$|A|>B \Leftrightarrow \left[ \begin{array}{l} A > B \\ A < -B \end{array} \right.$ &
$|A|\geq B \Leftrightarrow \left[ \begin{array}{l} A \geq B\\A\leq -B \end{array} \right.$
\\
&\\[-.5\normalbaselineskip]
\hline
&\\[-.5\normalbaselineskip]
$\sqrt{A}>B \Leftrightarrow \left[ \begin{array}{l} \begin{cases}B < 0\\A\geq 0\end{cases} \\[4ex] \begin{cases}B\geq 0\\A>B^2\end{cases} \end{array} \right.$ &
$\sqrt{A}\geq B \Leftrightarrow \left[ \begin{array}{l} \begin{cases}B < 0\\A\geq 0\end{cases} \\[4ex] \begin{cases}B\geq 0\\A\geq B^2\end{cases} \end{array} \right.$ \\[2.75\normalbaselineskip]
\hline
\end{tabular}

\end{document}


A different implementation with booktabs:

\documentclass[12pt,a4paper]{article}

\usepackage{amsmath,booktabs,array}

\begin{document}

$\begin{array}{ @{} l @{} >{{}}c<{{}} @{} l @{\qquad} l @{} >{{}}c<{{}} @{} l @{} } \toprule \addlinespace |A|>B & \Leftrightarrow & \left[ \begin{array}{l} A > B \\ A < -B \end{array} \right. & |A|\geq B & \Leftrightarrow & \left[ \begin{array}{l} A \geq B\\A\leq -B \end{array} \right. \\ \addlinespace \midrule \addlinespace \sqrt{A}>B & \Leftrightarrow & \left[ \begin{array}{l} \begin{cases}B < 0\\A\geq 0\end{cases} \\ \addlinespace \begin{cases}B\geq 0\\A>B^2\end{cases} \end{array} \right. & \sqrt{A}\geq B & \Leftrightarrow & \left[ \begin{array}{l} \begin{cases}B < 0\\A\geq 0\end{cases} \\ \addlinespace \begin{cases}B\geq 0\\A\geq B^2\end{cases} \end{array} \right. \\ \addlinespace \bottomrule \end{array}$

\end{document}


This allows you to manually adjust the size of the \lbrace. I wouldn't advise using it, however.

\documentclass[12pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath,amsfonts,amssymb}

\begin{document}
$\left\lbrace\rule{0pt}{2.5ex}\right. \begin{array}{@{}l@{}}B\geq 0\\A\geq B^2\end{array}$
\end{document}