# How can we give a single number for a system of equations?

I want to type the following equation, as it is.. I need the left flower to be right and the numbering also should be right..

How I can do that?

Do we have an environment like \begin{cases}...\end{cases}?

## My work:

I tried out with the following codes, but with that I am getting left brace only and that also very closed to the argument.

I want that the bracket has to be right.

\begin{equation}
\begin{cases}
TT^\dagger = Q\\
T^\dagger T T^\dagger =T^\dagger\\
T^\dagger T =(I-P)\\
TT^\dagger =Q.
\end{cases}
\end{equation}


And my output is ... • Have you tried with the cases environment ? If yes, can you send your Minimal Working Example ? – Jérôme Dequeker Dec 10 '15 at 14:18
• mathtools provides an rcases environment which puts the brace on the right. – campa Dec 10 '15 at 14:34
• 'rcases? k I will try that.. – David Dec 12 '15 at 9:06
• can you give me a link for that? @campa – David Dec 12 '15 at 9:10

Use an array:

\begin{equation}
\left.\begin{array}{l}
TT^\dagger = Q\\
T^\dagger T T^\dagger =T^\dagger\\
T^\dagger T =(I-P)\\
TT^\dagger =Q.
\end{array}\right\}
\end{equation}


I would go for something like this:

\documentclass[leqno]{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\left.
\begin{array}{l}
TT^\dagger = Q\\
T^\dagger T T^\dagger =T^\dagger\\
T^\dagger T =(I-P)\\
TT^\dagger =Q.
\end{array}
\right\]
\end{equation}
\end{document} BTW, if the dagger means transpose I would tend to use $T^{\top}$` instead.