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Show inline math as if it were display math

Whenever I try to get something below the product character, it actually puts it next to it.

The recommended code to do this is \Prod_{n=1}, but contrary to the example, for me it looks more like Nn=1 than actually below the prod character.

It does not mention a specific package though.

How to do this?

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You are probably in inline math mode $\prod_n$ try display math \[\prod_n\] or if you want that form inline $\displaystyle\prod_n$ –  David Carlisle Dec 1 '12 at 12:11
    
\Prod doesn't even exist for me. If you use \prod may be you are not in display math. If you use $\prod_{n=1}$ it will show as you said. If you use \[ \prod_{n=1} \] or $\displaymath \prod_{n=1}$ it should work. May be a little bit late... –  Manuel Dec 1 '12 at 12:13
2  
If you want to badly spoil your document, use $\prod\limits_{n=1}^{\infty}...$. If you want to have a preposterously horrible document, use $\displaystyle\prod_{n=1}^{\infty}$ –  egreg Dec 1 '12 at 12:16
2  
In the question's title, you mention \Pi as a possibility for creating a product symbol. Don't do it! Be sure to use the command \prod instead (with \limits if you absolutely have to set index of multiplication below the symbol). –  Mico Dec 1 '12 at 12:21
    
@Mico Thanks. egreg, I don't see the problem with the \limits method. –  Dualinity Dec 1 '12 at 12:51
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marked as duplicate by Mico, Count Zero, Kurt, Thorsten, egreg Dec 1 '12 at 13:18

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1 Answer

up vote 3 down vote accepted

In textstyle the limits (the n=1 in that case) are pushed to the right of the operator, while in displaystyle it is above and below.

The style used to display the formula depends on where it is in the text (inline in text or in an equation-like environment), and where it is in the formula (for example, in matrices or fractions, the subformulas are in text style by default).

In any case, you can use {\displaystyle \prod_{n=1}^{\infinity} a_n} to locally force the display style. Do it at your own risks, as the formula will become much taller, and is likely to break the appearance of your paragraph.

If you'd prefer a compromise, you can use the \limits command to force the limits to be placed above and below the operator, without changing the operator size (which \displaystyle does). Beware, even if the operator isn't resized, the limits will still enlarge the formula a bit and add to your line spacing.

In my humble opinion, these options are worth knowing, but should be restricted to cases where the formula has to appear correctly inside of a fraction or matrix. For inline formulas, the default text style is okay.

An example :

\documentclass{article}

\usepackage{amsmath}

\begin{document}

This is an inline formula : $\prod_{i=1}^{\infty} a_{i}$, \\
and now this is the same inline formula in display style : ${\displaystyle \prod_{i=1}^{\infty} a_{i}}$, \\
and now this is the same inline formula with limits : $\prod\limits_{i=1}^{\infty} a_{i}$

Now the same formula in an equation:
\begin{equation*}
  \prod_{i=1}^{\infty} a_{i}
\end{equation*}
or in an equation, but in a fraction :
\begin{equation*}
  \frac{\prod_{i=1}^{\infty} a_{i}}{2}
\end{equation*}
or in an equation, but in a fraction, but with forced display style :
\begin{equation*}
  \frac{\displaystyle \prod_{i=1}^{\infty} a_{i}}{2}
\end{equation*}


\end{document}

Example

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It was explained in the comments. However, I think you forget the option of including \limits which would be a good suggestion? It does not have the huge "forced display" style, but a smaller version. –  Dualinity Dec 1 '12 at 12:52
    
@Dualinity : Comments were posted at the same time as I was posting this. But thanks, you're right, I'll add the \limits. –  T. Verron Dec 1 '12 at 13:09
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