1

Do you have any aesthetically nice suggestion to solve the bad box given by the following formula?

\documentclass[11pt, english, oneside, a4paper]{book}
\usepackage{amsmath}
\usepackage{enumerate}
\newtheorem{proof}{Proof}
\begin{document}
\begin{proof}
text blablabla text blablabla text blablabla text blablabla text blablabla text blablabla text blablabla 
\begin{enumerate}
\item blablabla
\begin{enumerate}
\item \begin{align*}
\nu : \pi[N] & \rightarrow  N \\
\pi(x) &\mapsto \begin{cases}
          \pi^{-1}(\pi(x))=x & \text{ if } x \in o \\
          \{\nu(\pi(y)): \pi(y) \in \pi(x) \}= \{y : \pi(y) \in   \pi(x)\}=x & \text{ otherwise }
         \end{cases}
\end{align*}
\end{enumerate}  
\end{enumerate}
\end{proof}
\end{document}

One solution can be

    \begin{align*}
   \nu : \pi[N] & \rightarrow  N \\
   \pi(x) &\mapsto \begin{cases}
      \pi^{-1}(\pi(x))=x & \text{ if } x \in \on\\
      \{\nu(\pi(y)): \pi(y) \in \pi(x) \}= & \\
      \{y : \pi(y) \in \pi(x)\}=x & \text{ otherwise }
     \end{cases}
 \end{align*}

but I do not like the result...

3
  • Thanks for the reply. You mean documentclass and usepackage are needed?
    – flos
    Mar 15, 2018 at 21:10
  • It is my second time posting here, so I need to practice
    – flos
    Mar 15, 2018 at 21:11
  • I ve edited the post. I hope it is clearer now.
    – flos
    Mar 15, 2018 at 21:32

1 Answer 1

3

May this will suit you?

\documentclass{article}
\usepackage{mathtools}

\begin{document}

\begin{align*}
   \nu \colon \pi[N] & \longrightarrow N \\
   \pi(x) &\longmapsto \begin{cases*}
          \pi^{-1}(\pi(x))=x & if x $ \in \text{on}$\\[0.3ex]
          \begin{multlined}[b]\{\nu(\pi(y)): \pi(y) \in \pi(x) \}\\[-0.2ex]= \{y : \pi(y) \in \pi(x)\}=x \end{multlined}& otherwise
         \end{cases*}
  \end{align*}

\end{document} 

enter image description here

5
  • It looks very pretty! My following question ist very stupid: how do make appear the image of the code ? Thanks!
    – flos
    Mar 15, 2018 at 21:39
  • I'm no sure to see what you mean, but there's a horizontal scrollbar at the bottom of the code window.
    – Bernard
    Mar 15, 2018 at 21:46
  • I mean, how did you put the image/picture of your solution on the page?
    – flos
    Mar 15, 2018 at 22:08
  • In the toolbar of the edit window, the sixth icon (looking like a mountain) is for inserting images.
    – Bernard
    Mar 15, 2018 at 22:14
  • 1

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