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This page says that amsmath supports the \checkmark symbol. However, when I try to implement this

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}

$\checkmark$

\end{document}

TeXWorks gives me the error

! Undefined control sequence.
recently read> \checkmark

What could be the problem here? Thanks all.

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marked as duplicate by tohecz, Kurt, mafp, zeroth, diabonas Feb 28 '13 at 23:09

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2  
Add \usepackage{amssymb} and Welcome to TeX.sx! –  hpesoj626 Feb 28 '13 at 21:55
    
Welcome to TeX.sx! The package amsmath is useful, but the symbols are loaded by amssymb. That page is wrong. –  egreg Feb 28 '13 at 21:56
    
Thanks both of you, that answers my question! –  Doubt Feb 28 '13 at 22:00
2  
The site detexify.kirelabs.org/classify.html let's you see which package is needed for which symbol, see How to look up a symbol, too. Yeah, and +1 for a perfect Minimal (non)-Working Example! –  tohecz Feb 28 '13 at 22:10
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1 Answer 1

up vote 9 down vote accepted

that page is mistaken. all the symbol names listed there are from amsfonts.

the original implementation of amsmath (then called amstex.sty after the non-latex original) loaded amsfonts, but amsmath does not. from the file amsmath.dtx:

%    A \latex/ package named \pkg{amstex} was created in 1988--1989 by
%    adapting \fn{amstex.tex} for use within \latex/. The \pkg{amsmath}
%    package is the successor of the \pkg{amstex} package. It was
%    substantially overhauled to integrate it with \latex/2e, which
%    arrived on the scene in 1994. It provides more or less the same
%    features, but there are quite a few organizational differences as
%    well as some new features and bug fixes. For example, the
%    \pkg{amstex} package automatically loaded the \pkg{amsfonts}
%    package, but the \pkg{amsmath} package does not. At the present
%    time (November 1999) user-level documentation of the commands
%    provided here is found in the AMSmath Users' Guide,
%    \fn{amsldoc.tex}.

so it's necessary to \usepackage{amsfonts} to get access to \checkmark. most of the rest of the cited page specifies amssymb, which is correct; amssymb loads amsfonts automatically, so it's not necessary to specify both if the additional symbols are needed.

do you know who is responsible for that page? it would be polite to let them know it should be corrected/updated.

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Thanks all! I have informed that site owner. –  Doubt Feb 28 '13 at 22:45
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