4

I want to write a limit with the "arrows' notation." This is, instead of \lim_{n \rightarrow \infty} x_{n} = x I want to use x_{n} \rightarrow_{n \rightarrow \infty} x. My problem is that with this last code, the n \rightarrow \infty appears down to the right of the arrow, and I would like it to appear below the arrow. How can I do that?

2
  • BTW, you can us \to instead of \rightarrow (reads better). Feb 13 '15 at 4:28
  • Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. Feb 13 '15 at 9:04
6

You can use the extensible arrow \xrightarrow provided by amsmath, which has two arguments, an optional one for text below the arrow and a mandatory one for text above the arrow

\xrightarrow[text below]{text above}

In your case you have to use

\xrightarrow[n \to \infty]{}

MWE

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\[
x_{n} \xrightarrow[n \to \infty]{} x
\]

\end{document} 

enter image description here

Note that in the limit it's better to use \to rather than \rightarrow

1

Here's a way with the amsmath package's \underset macro.

\documentclass{article}
\usepackage{amsmath}
\def\xtend{-\!\!\!}
\begin{document}
\[ x_{n} \underset{\scriptscriptstyle n \rightarrow \infty}{\xtend\xtend\rightarrow} x\]
\end{document}

enter image description here

Here's a way with a stack. the option argument (here [2pt]) controls the depth of the underset.

\documentclass{article}
\usepackage{stackengine}
\stackMath
\def\xtend{-\!\!\!}
\begin{document}
\[ x_{n} \mathrel{%
  \stackunder[2pt]{\xtend\xtend\rightarrow}{\scriptscriptstyle n \rightarrow \infty}} x\]
\end{document}

enter image description here

4
  • \underset sets the "limit" too far away from the main arrow. this would be a disaster in an in-line expression. Feb 13 '15 at 16:36
  • @barbarabeeton I agree. But being always joked with about doing everything via stacks, I thought I would show something using amsmath too. I guess I should stick with stacks 8^b Feb 13 '15 at 17:55
  • @barbarabeeton I would add that the other given answer (\xrightarrow) also ruins linespacing. Only the stacking approach (perhaps with a 0pt underset) looks nice inline. Feb 13 '15 at 17:59
  • well, the main arrow would look better if it were a little longer. at least the back-tip of the arrowhead shouldn't poke at the infinity. (actually, if i were copyediting something that contained that expression in text, i would encourage the author to find some other way.) Feb 13 '15 at 18:40

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