[Tex/LaTex] Two double-line equations need double left brackets

arraysbracketsequations

I have four lines of equations. The first two and the second two need to be grouped by a left bracket, and all four need to be grouped by one overall left bracket.

I am using an array within an equation. I can't manage to add the two 'inner' left brackets. The one big left bracket over all four equations is not a problem, which is the following:

\begin{equation}
    \left\{
      \begin{array}{lcl}
        1\\
        2\\
        3\\
        4
      \end{array}
    \right.
\end{equation}

And this seems to work just fine. But when I try the following

\begin{equation}
  \left\{
    \begin{array}{lcl}
      \left\{ 
        \begin{array}{lcl}
        1\\
        2
        \end{array}{lcl}
      \right.
    \end{array}
    \begin{array}{lcl}
      \left\{      
        \begin{array}{lcl}
        3\\
        4
        \end{array}
      \right.
    \end{array}
  \right.
\end{equation}

it doesn't work. I've tried some other changes, including changing to eqnarray, or changing the places of the brackets, but nothing seems to work. Now I am not sure how to solve this.

Best Answer

I think that some information about the actual expressions might be useful to decide which structure(s) would be best to use; in its present form (using arrays for the two subgroups), one could use a cases environment for the outer brace:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{equation}
\begin{cases}
      \left\{ 
        \begin{array}{lcl}
        1 \\
        2
        \end{array}
      \right. \\
      \left\{      
        \begin{array}{lcl}
        3 \\
        4
        \end{array}
        \right.
\end{cases}
\end{equation}

\end{document}

enter image description here

Here's another option, using a gather environment for the whole structure, and nested arrays:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{gather}
  \left\{
    \begin{array}{@{}l@{}}
      \left\{ 
        \begin{array}{lcl}
        1 \\
        2
        \end{array}
      \right. \\
      \left\{      
        \begin{array}{lcl}
        3 \\
        4
        \end{array}
      \right.
    \end{array}
  \right.
\end{gather}

\end{document}

enter image description here

By the way, your code has some typos like \end{array{lcl}.

Related Solutions

[Tex/LaTex] Break line within array or eqnarray

The environment align is probably the way to go here:

\documentclass[12pt]{article}
\usepackage{amsmath}

\begin{document}


\begin{align}
\lambda_{R,t} &= \dfrac{(C_{R,t}-\phi_c C_{R,t-1})^{-\sigma}} 
{P_t(1+\tau_t^c)} - \phi_c \beta \dfrac{(E_t C_{R,t+1}-\phi_c C_{R,t})^{- 
\sigma}}{P_t(1+\tau_t^c)} \\
Q_t &= \beta E_t{(1-\delta)Q_{t+1} + \lambda_{R,t+1}R_{t+1}U_{t+1}(1- 
\tau^k_{t+1})} \\ 
& - \lambda_{R,t+1}P_{t+1} \left[\Psi_1(U_t-1) + \dfrac{\Psi_2} 
{2}(U_t-1)^2 \right] \nonumber
\end{align}


\end{document}

You also have to use \nonumber in order to avoid having three equation numbers.

Hope that helps.

Romain

[Tex/LaTex] Two equations on the same line

I propose this solution, with a code borrowed on this site from @DavidCarlisle:

\documentclass{article}
\usepackage[utf8]{inputenc}%
\usepackage{tabularx} 
\usepackage{mathtools, nccmath}

\makeatletter
\newcommand{\leqnomode}{\tagsleft@true\let\veqno\@@leqno}%
\newcommand{\reqnomode}{\tagsleft@false\let\veqno\@@eqno}%
\newcommand*{\compress}{\@minipagetrue}
\makeatother

\begin{document}

Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text. Some text.

{\centering\compress
\begin{tabularx}{\linewidth}{>{\leqnomode}XX}
\begin{equation}
\begin{aligned}
       a & =b \\
    c & =d \\
       e & =f
\end{aligned}
\end{equation}
 &
 \begin{equation}
\begin{aligned}
x & =y \\
 y & =z \\
u & =v
\end{aligned}
\end{equation}
\end{tabularx} \vspace{-\baselineskip}}

 Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text.

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Break line within array or eqnarray

[Tex/LaTex] Two equations on the same line

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