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I am planning to have a .sty file for scibing notes. When modifying one that already exists online, I found that I could not use




either to change the usual white square to the black one. So, how would I do this?

On a similar note, if I wanted to add a blacktriangle, how would I do this?

In case, the answer depends on how the rest of the .sty file looks, I am most willing to point to the file I am modifying.

My .sty file:

 \newtheoremstyle{myplain}      {10pt}{10pt}{\itshape}{}{\scshape}{.}{.5em}{}
 \newtheoremstyle{mydefinition} {10pt}{10pt}{}{}{\scshape}{.}{.5em}{}
 \newtheoremstyle{myremark}     {10pt}{10pt}{}{}{\scshape}{.}{.5em}{}

 \renewcommand{\qedsymbol}{\blacksquare}   %replacing this line with 
                                           % does not work either.

 \newtheorem{lem}         [thm]{Lemma}
 \newtheorem{pro}         [thm]{Proposition}
 \newtheorem{cor}         [thm]{Corollary}
 \newtheorem{claim}       [thm]{Claim}
 \newtheorem{fact}        [thm]{Fact}

 \newtheorem{defn}       [thm]{Definition}
 \newtheorem{eg}         [thm]{Example}
 \newtheorem{assumption} [thm]{Assumption}
 \newtheorem{openproblem}[thm]{Open Problem}
 \newtheorem{problem}    [thm]{Problem}

 \newtheorem{remark}        [thm]{Remark}
 \newtheorem{conjecture}    [thm]{Conjecture}

 \numberwithin{equation} {lecture}
 \numberwithin{figure}   {lecture}
 \numberwithin{table}    {lecture}


share|improve this question
I am sure my tags are off. Will someone please fix it for me? – kan May 13 '12 at 11:59
Would you please add a MWE? – egreg May 13 '12 at 12:30
Sure, I'll do @egreg – kan May 13 '12 at 12:47
up vote 3 down vote accepted

You probably forgot to load amssymb:

\documentclass{amsart} % just to have `amsthm` preloaded
share|improve this answer
Oh, OK. It works. I have to load amssymb before loading my .sty file and use \ensuremath{}! – kan May 13 '12 at 13:17
@KannappanSampath You don't have to use \ensuremath: use $\blacksquare$, which is the correct way. – egreg May 13 '12 at 13:55

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