In our lecture script, we use the notion of disjoint set union. It uses a special symbol to differentiate the disjoint from the usual set union, where we add an extra dot inside of the \cup symbol. Is there something like a \bigudot? Or any other way to add a centered dot to any symbol?
[Tex/LaTex] Mathematical symbol for disjoint set union
amsmathsymbols
Related Solutions
Rotate \boxplus by 45 degrees:
\documentclass{article}
\usepackage{graphicx,amsmath,amssymb}
\DeclareRobustCommand{\diamondtimes}{%
\mathbin{\text{\rotatebox[origin=c]{45}{$\boxplus$}}}%
}
\begin{document}
$a\diamondtimes b$
$a\times b$
\end{document}
For a smaller version and an empty diamond (note that \diamond already exists, but gives a much smaller symbol):
\documentclass{article}
\usepackage{graphicx,amsmath,amssymb}
\DeclareRobustCommand{\diamondtimes}{%
\mathbin{\text{\scalebox{.75}{\rotatebox[origin=c]{45}{$\boxplus$}}}}%
}
\DeclareRobustCommand{\bdiamond}{%
\mathbin{\text{\scalebox{.75}{\rotatebox[origin=c]{45}{$\Box$}}}}%
}
\begin{document}
$a\diamondtimes b$
$a\bdiamond b$
\end{document}
A case for \ooalign. I provide two variants, in the first one, the D is in math mode; in the second one it is in sans-serif text-mode font (I like this one). The example code shows the symbol for all math styles:
The code:
\documentclass{article}
\usepackage{graphicx}
\newcommand\DUnion{
\mathop{\mathchoice
{\ooalign{$\displaystyle\bigcup$\cr\hss\scalebox{.65}{\raisebox{0.45ex}{$D$}}\hss}}
{\ooalign{$\textstyle\bigcup$\cr\hss\scalebox{.8}{\raisebox{0.5ex}{\tiny$D$}}\hss}}
{\ooalign{$\scriptstyle\bigcup$\cr\hss\scalebox{.45}{\raisebox{0.3ex}{$D$}}\hss}}
{\ooalign{$\scriptscriptstyle\bigcup$\cr\hss\scalebox{.38}{\raisebox{0.4ex}{$D$}}\hss}}
}
}
\newcommand\Dunion{
\mathop{\mathchoice
{\ooalign{$\displaystyle\bigcup$\cr\hss\scalebox{.65}{\raisebox{0.45ex}{\sffamily D}}\hss}}
{\ooalign{$\textstyle\bigcup$\cr\hss\scalebox{.9}{\raisebox{0.5ex}{\tiny\sffamily D}}\hss}}
{\ooalign{$\scriptstyle\bigcup$\cr\hss\scalebox{.45}{\raisebox{0.3ex}{\sffamily D}}\hss}}
{\ooalign{$\scriptscriptstyle\bigcup$\cr\hss\scalebox{.38}{\raisebox{0.3ex}{\sffamily D}}\hss}}
}
}
\begin{document}
$A\DUnion B\quad
{\displaystyle A\DUnion B}\quad
L_{A\DUnion B}\quad
M_{L_{A\DUnion B}}$
$A\Dunion B\quad
{\displaystyle A\Dunion B}\quad
L_{A\Dunion B}\quad
M_{L_{A\Dunion B}}$
\end{document}
Best Answer
Edit I thought amssymb provides
\cupdotwhich does what you want... but it doesn't.\usepackage{MnSymbol}provides\cupdotand\bigcupdotbut is incompatible withamssymbwhich is unfortunate.Sometimes disjoint union is depicted using
\sqcupwhich has the advantage of being inamssymb