设置集合并集的格式

Question

在示例中

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

如何获得i=1联合符号正下方的 和正上方的无穷大？

Answer 1

在这种情况下，正确的命令是\bigcup：你可以使用

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

但这会无可挽回地破坏您的文档。当公式是内联时，最好将限制设置在符号的侧面。在显示数学模式下，是\limits隐式的。请参阅以下示例并自行判断。

\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}