Align equal sign inside case with equal sign outside

Question

I want to align the equal sign inside the case with the equal sign outside. How to do that? I have read answers to these questions 1 2 3, but I'm still very clueless. Could anyone please help? Thanks!

\documentclass{article}
\usepackage{amsmath}
\begin{document}  
\begin{align*}
    v&=s\\
    \begin{cases}
    v'_x&=1\\
    v'_y&=2\\
    \end{cases}
\end{align*}
\end{document}

Zarko · Answer 1 · 2022-10-13T21:11:16.267

3

One way is drawing this set of equations:

\documentclass[border=5mm, preview]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,
                matrix}
\begin{document}
[
\begin{tikzpicture}
\matrix (a) [matrix of math nodes, 
             nodes = {inner ysep=2pt},
             column sep=-4pt
             ]
{
v       & = s   \
v'_x    & = 1   \
v'_y    & = 2   \
};
\draw[decorate,decoration={brace, mirror}] 
    (a-2-1.north -| a-3-1.west) -- (a-3-1.south west);
\end{tikzpicture}
]
\end{document}

edited Oct 13 '22 at 21:11

answered Oct 13 '22 at 12:40

Zarko

296,517

Thanks! I'm still a beginner. Let me try to understand it. :) – user2165 Oct 13 '22 at 12:48
Image server seems to be working again ... – Jasper Habicht Oct 13 '22 at 19:58
@JasperHabicht, thank you for info! Image added! – Zarko Oct 13 '22 at 20:10

score 3 · Answer 2 · answered Oct 13 '22 at 19:43

A possibility with the blkarray package:

    \documentclass{article}
    \usepackage{blkarray}
    \usepackage{amsmath}
\begin{document}

\[ \begin{blockarray}{r@{}l}
    v&amp;{}=s\\
    \begin{block}{\{r@{}l}
    v'_x &amp;{}=1\\
    v'_y&amp;{}=2\\
    \end{block}
\end{blockarray} \]

\end{document}

score 3 · Answer 3 · answered Oct 13 '22 at 19:48

Just adapt the code in https://tex.stackexchange.com/a/621802/4427

\documentclass{article}
\usepackage{amsmath}
\usepackage{nicematrix}
\begin{document}
[
\setlength{\arraycolsep}{0pt}
\begin{NiceArray}{r >{{}}c<{{}} l}
    v&=&s\[1ex]
    v'_x&=&1\[1ex]
    v'_y&=&2
\CodeAfter\SubMatrix{{2-1}{3-3}.
\end{NiceArray}
]
\end{document}

Align equal sign inside case with equal sign outside

3 Answers3