# Any reason why \blacksquare and \box are causing errors?

I am using the amsmath package. I just want a black box at the end of a proof, right-justified.

\blacksquare and \box both cause errors.

Actually, I'd prefer a musical quarter note if that's possible :)

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The wasysym package provides \quarternote. – Torbjørn T. Oct 7 '11 at 1:39
what, precisely, are the errors? the open square used by amsthm (not defined in amsmath) is the open box at location hex03 in the msam font if amsfonts are loaded, otherwise it's a drawn box. if you're using amsthm, you can simply \renewcommand{\qedsymbol}{...} with whatever symbol you want, but if you're not using amsthm, i can't help without knowing more. – barbara beeton Oct 7 '11 at 21:15
The \blacksquare is defined in amssymb. – ntc2 Jan 27 '14 at 9:18

Are you including the appropriate packages?

\documentclass{article}

\usepackage{amsmath}%
\usepackage{MnSymbol}%
\usepackage{wasysym}%

\begin{document}
$\blacksquare$  \halfnote \quarternote
\end{document}

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I was only including amsmath – iDontKnowBetter Oct 7 '11 at 1:14
The \blacksquare is defined in amssymb. – ntc2 Jan 27 '14 at 9:19
@mtc: Good point. So instead of \usepackage{MnSymbol} one can use \usepackage{amssymb}. – Peter Grill Jan 27 '14 at 13:40