93

In the example

$\cup^{i=1}_{\infty}F_i$

How do you get the i=1 directly below the union symbol and the infinity directly above?

Joseph Wright
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Trajan
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    You should use $\bigcup\limits_{i=1}^{\infty} F_{i}$, but in inline math mode it's better to set the limits on the side (just don't use \limits, which is implicit in display math mode). Note that MathJax is not used on this site, because we don't want the code to become an approximation of the result, but want to talk about the code itself. – egreg Oct 08 '14 at 11:13

1 Answers1

128

The correct command to use in this case is \bigcup; you could go with

$\bigcup\limits_{i=1}^{\infty} F_{i}$

but this will irremediably spoil your document. When a formula is inline, it's better if limits are set to the side of the symbol. In display math mode the \limits is implicit. See the following example and judge for yourself.

\documentclass{article}
\begin{document}

The correct command to use in this case is \verb|\bigcup|;
if you use \verb|\limits| your formula will appear inline
like $\bigcup\limits_{i=1}^{\infty} F_{i}$, but this will
irremediably spoil your document. When a formula is inline,
it's better if limits are set to the side of the symbol. In
display math mode the \verb|\limits| is implicit. Here is the
same formula without it $\bigcup_{i=1}^{\infty} F_{i}$ and you
can clearly see that the vertical spacing is much better.
In a display there is no problem
\[
\bigcup_{i=1}^{\infty} F_{i}
\]
and the limits can be set above and below without spoiling
the spacing, which is an important factor when readability
is considered.

\end{document}

enter image description here

egreg
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