[Tex/LaTex] LaTeX symbol for “\leftrightarrow” with “\triangleq”

Question

In LaTeX, does it exist any symbol for

Answer 1

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}