1

I have a mathematical note as follows;

$$\left.\begin{array}{rl}
x\notin f(C)\overset{C\cap f^{-1}(D)\subseteq C}{\longrightarrow} & x\notin f\big(C\cap f^{-1}(D)\big)\\
& x\in U
\end{array}\right\}\Longrightarrow x\in V$$

But as you are seeing the arrow is small in comparing with its superscript and the shape of the equation is not interesting. I would to use the idea at this question, using \scalebox{}{\(\)} as follows but it scales the arrow both horizontal and vertical so again the shape of the equation is not interesting. I will be thankful for any other suggestion.

$$\left.\begin{array}{rl}
x\notin f(C)\overset{C\cap f^{-1}(D)\subseteq C}{\scalebox{2}{\(\longrightarrow\)}} & x\notin f\big(C\cap f^{-1}(D)\big)\\
& x\in U
\end{array}\right\}\Longrightarrow x\in V$$

2 Answers 2

4

I think that you should use the \xrightarrow macro and the rcases environment of the mathtools package. Using these you can produce

enter image description here

using the relatively simple code

\documentclass{article}
\usepackage{mathtools}
\begin{document}

\[
  x\notin f(C)\xrightarrow{C\cap f^{-1}(D)\subseteq C}
    \begin{rcases}
      & x\notin f\big(C\cap f^{-1}(D)\big)\\
      & x\in U
    \end{rcases}
    \Longrightarrow x\in V
\]

\end{document}

Note, in particular, that I have replaced your $$..$$ with \[...\]

3
  • Thank you so much (but $x\in U$ can't be implied from $x\notin f(C)$ plus $C\cap f^{-1}(D)\subseteq C$). And what is the difference of double dollors and the other sign you used? My problem just solved by replacing \overset{}{} by \xrightarrow{}. Commented Nov 8, 2014 at 8:18
  • For the difference between double dollar signs and \[...\] see why-is-preferable-to. As regards the mathematics, I just typeset what you had -- as did Peter Gill:)
    – user30471
    Commented Nov 8, 2014 at 8:47
  • Thank you for the link to why \[...\] is preferable. But about what I wrote, it was a 2 times 2 array with empty entry at second row-first column, so the result is different than what you both have written. Commented Nov 8, 2014 at 9:25
2

You can also use tikz for the overkill solution, but gives you a lot of flexibility in terms of the arrow tip, line thickness and color:

enter image description here

Code:

\documentclass{article}
\usepackage{mathtools}
\usepackage{tikz}

\makeatletter
\newcommand*{\MyArrow}[2][]{%
    \mathbin{%
        \tikz[baseline,remember picture] \node[above, inner sep=1pt, #1, draw=none] (X) at (0,0.5ex) {$\scriptstyle #2$};
        \tikz[baseline,remember picture,overlay] \draw [->, #1] (X.south west) -- (X.south east);
    }%
}
\makeatother

\newcommand{\Rhs}{%
    \begin{rcases}
      & x\notin f\big(C\cap f^{-1}(D)\big)\\
      & x\in U
    \end{rcases}
    \Longrightarrow x\in V 
}%

\begin{document}

\begin{gather}
  x\notin f(C)\MyArrow{C\cap f^{-1}(D)\subseteq C} \Rhs \\
  x\notin f(C)\MyArrow[-latex,draw=red]{C\cap f^{-1}(D)\subseteq C} \Rhs \\
  x\notin f(C)\MyArrow[-stealth,draw=blue,thick]{C\cap f^{-1}(D)\subseteq C} \Rhs \\
\end{gather}

\end{document}
1
  • Thank you so much (but $x\in U$ can't be implied from $x\notin f(C)$ plus $C\cap f^{-1}(D)\subseteq C$). It was too nice to be able to customize shapes of arrows. I like this answer so upvoted it but as the first answer was more simple I chose that one as the answer. I think I will use your suggestions many times in my notes (but not in things like thesis and official ones). Commented Nov 8, 2014 at 8:17

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