# Numbered equation, alignedat enviroment, tall curly brace [duplicate]

I want to get a single equation number for this multiple equation with \label I need for cross referencing. Also, I need a tall curly brace prior to the equation number.

mathtools has rcases

\documentclass{article}

\usepackage{mathtools}

\begin{document}

\label{eq:abc} \begin{rcases} \begin{alignedat}{3} \log L&=0 && \implies &u_1&=x\\ \log L&=0 && \implies &u_2&=y \end{alignedat} \end{rcases}
See \eqref{eq:abc}
\end{document}


You can use alignedat, but you can exploit that the two equations have the same structure and the same width.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\left. \begin{alignedat}{3} \frac{\partial}{\partial\mu_1}\log L &= 0 &\enspace\Rightarrow &\enspace& \hat{\mu}_1&=\bar{x}_1 \\ \frac{\partial}{\partial\mu_2}\log L &= 0 &\enspace\Rightarrow &\enspace& \hat{\mu}_2&=\bar{x}_2 \end{alignedat} \right\}

$$\left. \begin{gathered} \frac{\partial}{\partial\mu_1}\log L = 0 \;\Rightarrow\; \hat{\mu}_1=\bar{x}_1 \\ \frac{\partial}{\partial\mu_2}\log L = 0 \;\Rightarrow\; \hat{\mu}_2=\bar{x}_2 \end{gathered} \right\}$$

\end{document}


Here's a solution that encases an array environment in a \left. ... \right\} construct.

\documentclass{article} % or some other suitable document class

\usepackage{array} % for '\newcolumntype' macro
\newcolumntype{C}{>{{}}c<{{}}} % for mathbin and mathrel objects
\newcolumntype{L}{>{\displaystyle}l}
\newcolumntype{R}{>{\displaystyle}r}

\setlength\textwidth{4in}  % just for this example
\counterwithin{equation}{section}
\begin{document}
\setcounter{section}{16}   % just for this example
\setcounter{equation}{44}

$$\label{eq:hello} \setlength\arraycolsep{0pt} % default value: 5pt \left. \begin{array}{ RCL @{\quad} c @{\quad} RCL } \frac{\partial}{\partial\mu_1} \log L &=& 0 &\Rightarrow& \hat{\mu}_1 &=& \bar{x}_1 \\ \addlinespace \frac{\partial}{\partial\mu_2} \log L &=& 0 &\Rightarrow& \hat{\mu}_2 &=& \bar{x}_2 \end{array} \right\}$$
A cross-reference to equation (\ref{eq:hello}).
\end{document}


Another solution, with the drcases environment, to ensure \displaystye inside rcases, and the diffcoeff package, which eases typesetting partial derivatives (and also ordinary derivatives):

    \documentclass{article} % or some other suitable document class

\usepackage{mathtools}
\usepackage{diffcoeff}

\begin{document}

$$\label{eqn} \begin{drcases} \diffp*{\log L}{\mu_1} = 0 \implies & \widehat{\mu}_1 = \bar{x}_1 \\[1ex] \diffp*{\log L}{\mu_2} = 0 \implies & \widehat{\mu}_2 = \bar{x}_1 \end{drcases}$$

\end{document}