The size of arrow in an equation is not suitable

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$$}} & x\notin f\big(C\cap f^{-1}(D)\big)\\ & x\in U \end{array}\right\}\Longrightarrow x\in V$$


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

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 $...$

• 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

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:

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}

• 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