# LaTeX symbol for “\leftrightarrow” with “\triangleq”

In LaTeX, does it exist any symbol for

Here are two possible alternatives. In both cases (\symA and \symB), I use both a left and right arrow joined in order to get a wider arrow. The \mkern can be increased negatively, if you want the width narrower. The \symA uses the \triangleq component from amssymb, but the vertical gap can be controlled with the optional argument to \stackon. The \symB does not require amssymb, but tries to mimic the tapered equal sign you showed in your figure, by using stacked \rules. Again, the vertical spacings are adjustable.

\documentclass{article}
\usepackage[usestackEOL]{stackengine}
\usepackage{amssymb}
\def\symA{\mathrel{\stackon[-0.8pt]{\leftarrow\mkern-6mu\rightarrow}%
{\scriptstyle\triangleq}}}
\def\symB{\mathrel{\stackon[.7pt]{\leftarrow\mkern-6mu\rightarrow}%
{\setstackgap{S}{0pt}\Shortstack{%
\scriptscriptstyle\triangle\\\rule[.8pt]{6pt}{0.25pt}\\\rule{8pt}{.25pt}}}}}
\stackMath
\begin{document}
$A \symA B \symB C$
\end{document}


There is no ready made symbol per se, but you can definitely create a new one.

Simply define a new macro using either \mathbin or \mathrel. I think that you will need the later one, since an arrow usually shows a relation.

Please see here two understand the subtle differences between the two solutions.

You use the \overset command to stack up your operators.

\documentclass{article}

\usepackage{amsmath}

\usepackage{amssymb}

\newcommand{\leftrightarrowtriangleqbin}{\mathbin{\overset\triangleq\leftrightarrow}}

\newcommand{\leftrightarrowtriangleqrel}{\mathrel{\overset\triangleq\leftrightarrow}}

\begin{document}

$S \leftrightarrowtriangleqbin T$

$S \leftrightarrowtriangleqrel T$

\end{document}


And here is a sample output.

See the subtle spacing difference between the two?

Actually, for the second one \mathrel around the construction is redundant. As pointed out by egreg below, \overset will keep the binary relation nature of its second argument.

• \DeclareMathOperator? Just a new command with \mathrel enclosing the code… – Manuel Dec 29 '13 at 16:30
• @Manuel Yes, may be. Depends on the context the symbols will be used. – Masroor Dec 29 '13 at 16:35
• It has nothing to do with \DeclareMathOperator which is not suited for this situation. By the way, an arrow usually shows a relation. Like (almost?) all the arrows defined in Latex, I would use \newcommand\leftrightarrowtriangleq{\mathrel{\overset\triangleq\leftrightarrow}}. – Manuel Dec 29 '13 at 16:41
• You can edit your answer if you think my comment is right. It was written as a suggestion to your answer, not as an answer to the original question. – Manuel Dec 29 '13 at 16:50
• @Manuel \overset{\triangleeq}{\leftrightarrow} is sufficient, because \overset will keep the "binary relation" nature of its second argument. So \mathrel around the construction is redundant. – egreg Dec 29 '13 at 16:53