[Tex/LaTex] Align some equations in empheq environment

alignempheqhorizontal alignment

I am trying to align some equations in an empheq environment but cannot get it right. Here is my MWE:

\documentclass{article}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{empheq}
\usepackage{amsfonts}

\newcommand{\integers}[2]{[\![#1,#2]\!]}

\begin{document}

Test 1:
\begin{empheq}{align}
&\max~w_1 \sum_{i,j} t_{ij}(1-x_{ij})+w_2 gl\sum_{i,j} \Big(4x_{ij}-\sum_{(p,q)\in A_{ij}} z_{ijpq}\Big)&&\\
& z_{ijpq} \leq y_i &\forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \leq y_j &\forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \geq y_i + y_j - 1 &\forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& x_{ij} \in \{0,1\}&\forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \in \{0,1\}&\forall i,p \in \integers{1}{m}, \forall j,q \in \integers{1}{n}
\end{empheq}

Test 2:

\begin{empheq}{align}
a&=b\\
E&=mc^2 + \int_a^a x\, dx
\end{empheq}


\end{document}

Test2 comes from the empheq documentation. Here are my two questions:

Test2 is aligned left, as expected, but Test1 is not. How can I align all left in Test1?

The first equation of Test1 being very long, I would like to ignore it in the align, and get something like this (the green lines show the alignment I am looking for):

I tried something which does not compile:

\begin{empheq}[left=(P_2)\empheqlbrace]
\max~w_1 \sum_{i,j} t_{ij}(1-x_{ij})+w_2 gl\sum_{i,j} x_{ij}\Big(4-\sum_{(p,q)\in A_{ij}} x_{pq}\Big)\\
\begin{align*}
& x_{ij} \in \{0,1\} &forall i \in \integers{1}{m}, j \in \integers{1}{n}
\end{align*}
\end{empheq}

I found this on StackExchange but I couldn't make it work with empheq.

Best Answer

with use of alignat=3 you can obtain:

edit as noted barbara beeton in her comment below (thank you very much!), if really want to left-align the column on the right, you should use &&:

\documentclass{article}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{empheq}
\usepackage{amsfonts}

\newcommand{\integers}[2]{[\![#1,#2]\!]}

\begin{document}

Test 1:
\begin{empheq}{alignat=3} % <---
& \max~w_1 \sum_{i,j} t_{ij}(1-x_{ij})
                        && + w_2 gl\sum_{i,j} \Big(4x_{ij}-\sum_{(p,q)\in A_{ij}} z_{ijpq}\Big)\\
& z_{ijpq} \leq y_i     &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \leq y_j     &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \geq y_i + y_j - 1
                        &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& x_{ij} \in \{0,1\}    &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \in \{0,1\}  &&   \forall i,p \in \integers{1}{m}, \forall j,q \in \integers{1}{n}
\end{empheq}

Test 2:

\begin{empheq}{align}
a&=b\\
E&=mc^2 + \int_a^a x\, dx
\end{empheq}

\end{document}

The very same result can be obtain without use of empheq environment:

\begin{alignat}{3} % <---
& \max~w_1 \sum_{i,j} t_{ij}(1-x_{ij})
                        && + w_2 gl\sum_{i,j} \Big(4x_{ij}-\sum_{(p,q)\in A_{ij}} z_{ijpq}\Big)\\
& z_{ijpq} \leq y_i     &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \leq y_j     &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \geq y_i + y_j - 1
                        &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& x_{ij} \in \{0,1\}    &&   \forall i \in \integers{1}{m}, j \in \integers{1}{n}\\
& z_{ijpq} \in \{0,1\}  &&   \forall i,p \in \integers{1}{m}, \forall j,q \in \integers{1}{n}
\end{alignat}

Test 2:
\begin{align}
a&=b\\
E&=mc^2 + \int_a^a x\, dx
\end{align}

Related Solutions

[Tex/LaTex] Force to align left a empheq box

You just need to add the option fleqn to your document class line.

Here is the full code:

\documentclass[fleqn]{article}
\usepackage{xcolor}
\usepackage{tcolorbox}
\tcbuselibrary{skins,theorems}
\usepackage{empheq}
\newtcbox{\resultbox}[1][lightgray]{
    nobeforeafter,
    math upper,
    tcbox raise base,
    enhanced,
    boxrule=1pt,
    colback = #1!30,
    drop lifted shadow,
    sharp corners
}

\begin{document}

    \begin{empheq}[box=\resultbox]{equation*}
        v(t) = 2\alpha t - \gamma\omega sen(\omega t))
    \end{empheq}

\end{document}

Next time please give a full minimal working example. In particular, the code should compile.

EDIT to typeset equation on the left without setting fleqn globally

The fleqn option sets a flag @fleqn that is used by the empheq package to typeset the equation on left. The hack below sets this flag when the package is loaded and then creates a new environment Empheq that sets this flag for the environment only. With this in place, you can have your cake and eat it too, so to speak.

\documentclass{article}
\usepackage{xcolor}
\usepackage{tcolorbox}
\tcbuselibrary{skins,theorems}
\newtcbox{\resultbox}[1][lightgray]{
    nobeforeafter,
    math upper,
    tcbox raise base,
    enhanced,
    boxrule=1pt,
    colback = #1!30,
    drop lifted shadow,
    sharp corners
}
\makeatletter% hack to allow empheq environment to be used with fleqn in force only locally
\@fleqntrue
\usepackage{empheq}
\newenvironment{Empheq}{\@fleqntrue\empheq[box=\resultbox]{equation*}}{\endempheq}
\@fleqnfalse
\makeatother

\begin{document}

    \begin{Empheq}
        v(t) = 2\alpha t - \gamma\omega sen(\omega t))
    \end{Empheq}
    \begin{equation*}
        v(t) = 2\alpha t - \gamma\omega sen(\omega t))
    \end{equation*}

\end{document}

This produces:

I have typeset the equation normally underneath to highlight the difference. I have not tested this hack comprehensively. It is unlikely that it breaks something else as this is not the way the fleqn is meant to be used. In particular, other empheq environments in your document will almost certainly be broken.

[Tex/LaTex] How to make set of equations appear side by side using empheq package

Honestly I find empheq quite the overkill here.

\documentclass{article}

\usepackage[margin=.2in, paperwidth=8.5in, paperheight=11in]{geometry}
\usepackage{amsmath}% or empheq, which loads mathtools, which loads amsmath

\begin{document}
Lorem ipsum dolor sit et amet.
\[
\boxed{
\begin{aligned}
\sin(A+B)&=\sin A\cos B+\cos A\sin B\\
\sin(A-B)&=\sin A\cos B-\cos A\sin B\\
\cos(A+B)&=\cos A\cos B-\sin A\sin B\\
\cos(A-B)&=\cos A\cos B+\sin A\sin B
\end{aligned}}
\quad
\boxed{
\begin{aligned}
\sin(A+B)+\sin(A-B)&=2\sin A\cos B\\
\sin(A+B)-\sin(A-B)&=2\cos A\sin B\\
\cos(A-B)+\cos(A+B)&=2\cos A\cos B\\
\cos(A-B)-\cos(A+B)&=2\sin A\sin B
\end{aligned}}
\]
Lorem ipsum dolor sit et amet.
\end{document}

You need an awfully small margin to fit that though...

Best Answer

Related Solutions

[Tex/LaTex] Force to align left a empheq box

[Tex/LaTex] How to make set of equations appear side by side using empheq package

Related Question