# Curly Bracket size and appearance

I have the following MWE:

\documentclass[12pt, A4paper]{article}
\usepackage{mathtools}
\usepackage[left=2cm, right=2cm, top=2cm,bottom=2cm]{geometry}
\DeclarePairedDelimiter\set\{\}

\begin{document}
\begin{align}
\mathcal{T}^R=&\set[\Bigg]{\frac{\Gamma+2\Theta\times PC^R}{\sqrt{var(\Gamma)+var(\Theta)\times \left[2PC^{R}\right]^2+covar(\Gamma\Theta)\times{2PC^R}}}<-t_{\alpha}} \nonumber \\
& \set[\Bigg]{\frac{\Gamma+2\Theta\times PC^R}{\sqrt{var(\Gamma)+var(\Theta)\times \left[2PC^{R}\right]^2+covar(\Gamma\Theta)\times{2PC^R}}}>t_{\alpha}}
\end{align}
\end{document}


I have two problems:

1) The curly brackets are not big enough to cover the entire equation;

2) Ideally I would like to eliminate the curly bracket on the right in the first line and the one on the left in the second line. I tried with \phantom but it did not work.

Any suggestion?

EDIT: I was able to eliminate the brackets using \left\{ and \right. But still the brackets are not large enough to cover the entire equation.

My MWE is now:

\documentclass[12pt, A4paper]{article}
\usepackage{mathtools}
\usepackage[left=2cm, right=2cm, top=2cm,bottom=2cm]{geometry}

\begin{document}
\begin{align}
\mathcal{T}^R=&\left\{\frac{\Gamma+2\Theta\times PC^R}{\sqrt{var(\Gamma)+var(\Theta)\times \left[2PC^{R}\right]^2+covar(\Gamma\Theta)\times{2PC^R}}}<-t_{\alpha} \right. \nonumber \\
& \left.\frac{\Gamma+2\Theta\times PC^R}{\sqrt{var(\Gamma)+var(\Theta)\times \left[2PC^{R}\right]^2+covar(\Gamma\Theta)\times{2PC^R}}}>t_{\alpha}\right\}
\end{align}
\end{document}

• Removing \left and \right cures the problem of the too big radical. Use ={}& to fix the spacing; don't forget to define operator names for “var” and “covar”. – egreg Sep 6 '18 at 13:28
• On the other hand, it's quite hard to understand the meaning of that equation: what's the dummy variable in the set denotation? – egreg Sep 6 '18 at 13:38
• @egreg I agree. I did not copy the entire explanation of the equation. I presume you are referring to R. In that case R stands for High and Low. I wrote this just after the equation in my paper. – Dario Sep 6 '18 at 13:49

For 1), simply remove \left, \right under the square root. In addition the 2 exponent will have a better placement.

For 2), we can use Sébastien Gouezel \MTkillspecial command, which allows line breaks with alignments within paired delimiters (p.29-30 of mathtools documentation).

I added some improvements, among which the alignment of the two lines on their ends.

\documentclass[12pt, a4paper]{article}
\usepackage{mathtools}
\usepackage[margin=2cm]{geometry}
\DeclarePairedDelimiter\set\{\}

\newcommand\MTkillspecial[1]{% helper macro
\bgroup
\catcode\&=9
\let\\\relax%
\scantokens{#1}%
\egroup
}
\reDeclarePairedDelimiterInnerWrapper\set{star}{
E\mathopen{#1\vphantom{\MTkillspecial{#2}}\kern-\nulldelimiterspace\right.}
#2
\mathclose{\left.\kern-\nulldelimiterspace\vphantom{\MTkillspecial{#2}}#3}}

\DeclareMathOperator{\var}{var}
\DeclareMathOperator{\covar}{covar}

\begin{document}

\begin{align}
\mathcal{T}^R= \set[\Bigg]{\frac{\Gamma+2\Theta\times PC^R}{\sqrt{\var(\Gamma)+\var(\Theta)\times[2PC^{R}]^2+ \covar(\Gamma\Theta)\times{2PC^R}}}<-t_{\alpha}& \notag\\
\frac{\Gamma+2\Theta\times PC^R}{\sqrt{\var(\Gamma)+\var(\Theta)\times [2PC^{R}]^2+\covar(\Gamma\Theta)\times{2PC^R}}}>t_{\alpha} &}
\end{align}

\end{document}
`