[Tex/LaTex] Symbol for disjoint union

symbols

I found two symbols for the disjoint union. One is the union with a dot and I can do it. The other possibility is to put a small 'D' inside the union and this is what I don't find in any list of symbols I've checked. Could some one help me with this??Thank you so much!

Best Answer

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:

enter image description here

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}
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