15

I want to have a product sign analogously to $A \amalg B$. I tried $A \Pi B$, but as $\Pi$ isn't a binary operator, this does not look that good.

Can you help me?

2
  • 1
    You can try drawing the symbol at detexify; if it can find a match, it will tell you the command for the symbol and which package it's loaded with.
    – ChrisS
    Jul 31, 2013 at 9:00
  • 2
    \coprod, \prod, \amalg, \Pi. You can find those with my classifier write-math.com Apr 28, 2015 at 10:08

2 Answers 2

19

Use \mathbin to fix the spacing issue.

\documentclass{article}
\newcommand*\productop{\mathbin{\Pi}}

\begin{document}
\[ a \amalg b \qquad a \productop b\]
\end{document}

enter image description here

0
18

Another solution is to rotate 180° the symbol \amalg (requires graphicx) to get exactly the same symbol upside down:

\documentclass{article}
\usepackage{graphicx}

\newcommand{\invamalg}{\mathbin{\rotatebox[origin=c]{180}{$\amalg$}}}

\begin{document}
\[ A \amalg B \qquad A \invamalg B\]
\end{document}

enter image description here

To get a size changing symbol you can load the amsmath package and modify the \newcommand line as follows (thanks to egreg for the suggestion):

\newcommand{\invamalg}{\mathbin{\text{\rotatebox[origin=c]{180}{$\amalg$}}}}

In this way you can use the new defined command even in subscripts and superscripts. The following MWE

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}

\newcommand{\invamalg}{\mathbin{\text{\rotatebox[origin=c]{180}{$\amalg$}}}}

\begin{document}

\[
 A \invamalg B_{A \invamalg B_{A \invamalg B}}
\]

\[
 A \amalg B_{A \amalg B_{A \amalg B}}
\]

\end{document}

gives the result:

enter image description here

3
  • \amalg is slightly different from a reversed \Pi. You can get a size changing symbol by loading amsmath and putting \rotatebox[...]{180}{...} inside \text.
    – egreg
    Jul 31, 2013 at 9:29
  • With \mathchoice{\text{...}} you're typesetting the symbol sixteen times instead of the four with the \text method and the result is exactly the same (\text already does \mathchoice by itself). There's no need to load \mathtools in order to have \mathchoice, which is a primitive of TeX.
    – egreg
    Jul 31, 2013 at 11:57
  • @egreg I've deleted that solution. Thanks for pointing it out. Jul 31, 2013 at 13:54

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