How to generate \biguminus math symbol?

Question

How do I create a \biguminus symbol which is similar to \biguplus except there is a minus sign instead of plus sign?

Answer 1

You can use \ooalign.

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\newcommand*\biguminus{\mathop{\mathpalette\@biguoperator{-}}}
\newcommand*\bigutimes{\mathop{\mathpalette\@biguoperator{\times}}}
\newcommand*\bigucdot{\mathop{\mathpalette\@biguoperator{\cdot}}}
\newcommand*\@biguoperator[2]{\ooalign{\hidewidth$#1\m@th#2$\hidewidth\cr$#1\m@th\bigcup$\cr}}
\makeatother
\begin{document}

\[
  \biguplus_{\biguplus_{\biguplus}}
  \biguminus_{\biguminus_{\biguminus}}
  \bigutimes_{\bigutimes_{\bigutimes}}
  \bigucdot_{\bigucdot_{\bigucdot}}
\]

\end{document}