5

When I use $\iint_R f(x,y)dA$ the letter $R$ is to the right of the double integral sign. How to make it under the sign? This is a simple question but I couldn't find a related question.

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    @JouleV I managed to mess up the markdown quoting:-), I'll delete and repost the comment, thanks. – David Carlisle Apr 19 at 8:46
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    you are using inline mathematics ($) the entire design of the layout for inline math is to make it fit within the normal line spacing of the text in a paragraph so limits move to subscript position, if you need the display style it it best to set it as a math display(\[...\]) – David Carlisle Apr 19 at 8:46
  • @DavidCarlisle Thanks a lot! – Haoran Chen Apr 24 at 14:37
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Apart from JouleV's nice answer, you can use \limits option to typeset the inline with equation with limits under the integral symbol.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
$\iint\limits_a f(x,y) dA$
\end{document}

to get:

enter image description here

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    I'd say that \iint\limits_R centers the R term far better than \underset{R}{\iint} does. – Mico Apr 19 at 8:58
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    No upper limit should be used when \limits follows a command for multiple integrals. You should also respect the OP’s preference for the differential. – egreg Apr 19 at 9:09
  • @egreg I have updated my answer, thanks for the remark. Could you also briefly explain why no upper limit must be used? – Raaja Apr 19 at 9:13
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    @Raaja Because they’re badly positioned. – egreg Apr 19 at 9:14
  • @egreg Huhh, like that ;) thanks. – Raaja Apr 19 at 9:15
3

I don't think this is a good idea, but if you want to have it, you can use \underset:

\documentclass{standalone}
\usepackage{amsmath}
\begin{document}
$\underset{R}{\iint} f(x,y)dA$
\end{document}

enter image description here

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    Sorry, but this is not the best choice. – egreg Apr 19 at 9:10
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    @egreg Yes, it may not be the best, but it surely is a bad one. I will never write like that in my documents – user156344 Apr 19 at 9:19

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