symbols
I was simply messing around on a website called:
Detexify
just drawing various math symbols, when I came across a cool and interesting symbol of a fax machine. The following command for it being: \Faxmachine
My question was, does anyone know what package is needed to be able to compile with the command in the tex file because I keep getting undefined control sequence.
If I go to the detexify site and draw the double-integral-with-circle symbol, the answer I get is \oiint from the esint package. The package also provides the command \varoiint for a perfectly circular-shaped circle symbol. (Sounds rather circular, doesn't it?!)
Aside: If the esint package is loaded, the macros \iint and \oint are modified relative to the definitions provided by the amsmath package. With \iint, the two integral symbols are spaced more closely, and with \oint, the circle is enlarged. (Note that the shape of the basic integral symbol itself is still the one that's provided by the Computer/Latin Modern math font.) Speaking purely for myself, I find both changes to be ok, and even quite good. However, it's probably worth pointing this out explicitly, if for no other reason than to avoid any surprises by unsuspecting users of the esint package.
\documentclass{article}
\usepackage{esint} % various fancy integral symbols
\begin{document}
\[
\int \iint \oint \oiint \varoiint
\]
\end{document}
Addendum, March 2018: If you use LuaLaTeX and the unicode-math package, you wouldn't need to load any particular package to get access to macros such as \iint, \oint, and \oiint -- the corresponding symbols should be provided by just about all unicode-based math font. Here's how the symbols look when using 11 different math fonts. (Aside: I chose the math fonts purely based on their ability on my TeX distribution (MacTeX2018).)
% !TEX TS-program = lualatex
\documentclass{article}
\newcommand\blurb{$\displaystyle \int\ \iint\ \oint\ \oiint $}
\usepackage{unicode-math,booktabs}
%% Load 11 math fonts
\setmathfont{Latin Modern Math}[version=LM]
\setmathfont{Stix Math}[version=Stix]
\setmathfont{XITS Math}[version=XITS]
\setmathfont{Stix Two Math}[version=Stix2]
\setmathfont{Cambria Math}[version=Cambria]
\setmathfont{Asana Math}[version=Asana]
\setmathfont{TeX Gyre Pagella Math}[version=Pagella]
\setmathfont{TeX Gyre Termes Math}[version=Termes]
\setmathfont{TeX Gyre DejaVu Math}[version=DejaVu]
\setmathfont{Neo Euler}[version=Euler]
\setmathfont{Libertinus Math}[version=Libertinus]
\begin{document}
\begin{tabular}{@{}ll@{}}
Latin Modern Math & \mathversion{LM} \blurb \\ \addlinespace
Stix Math & \mathversion{Stix} \blurb \\ \addlinespace
XITS Math & \mathversion{XITS} \blurb \\ \addlinespace
Stix Two Math & \mathversion{Stix2} \blurb \\ \addlinespace
Cambria Math & \mathversion{Cambria} \blurb \\ \addlinespace
Asana Math & \mathversion{Asana} \blurb \\ \addlinespace
Pagella Math & \mathversion{Pagella} \blurb \\ \addlinespace
Termes Math & \mathversion{Termes} \blurb \\ \addlinespace
DejaVu Math & \mathversion{DejaVu} \blurb \\ \addlinespace
Neo Euler & \mathversion{Euler} \blurb \\ \addlinespace
Libertinus Math& \mathversion{Libertinus}\blurb
\end{tabular}
\end{document}
In the Comprehensive List (texdoc symbols) one can find something near to what you want, looking for \independent. Here's a modified version:
\documentclass{article}
\makeatletter
\DeclareRobustCommand{\varamalg}{%
\mathbin{\mathpalette\var@malg\perp}%
}
\newcommand\var@malg[2]{%
\rlap{$\m@th#1#2$}\mkern6mu{#1#2}%
}
\makeatother
\begin{document}
\[
\alpha\varamalg\beta=\alpha\times\{0\}\cup\beta\times\{1\}
\]
\end{document}
Adjust \mkern6mu to suit.
Best Answer
Actually Detexify always adds the necessary package to a symbol after presenting possible matches to what you have drawn. But you also can click on the „symbols“ button and enter the command. Here, too, the necessary package is added. So, in this case you will need the marvosym package.