TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

This question already has an answer here:

Recently in some LaTeX documentation I noticed that there is a special LaTeX command for the symbol meaning "corresponds to", which is similar to an equal sign with a hat on top. \hat{=} or \widehat{=} both do not give satisfying results (my personal view). Unfortunately, I cannot remember which documentation it was! Does anyone know the command or the documentation where to find it?

The symbol I am looking for:

The symbol I am looking for

PS: I have already tried detexify but it didn't produce anything useful! Also, browsing the comprehensive LaTeX symbol list wasn't successful.

share|improve this question

marked as duplicate by Joseph Wright Jun 27 '14 at 17:09

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
$\cong$ might be what you want. Other related symbols are \simeq, \sim, \approx. There is a symbol bible out on the web called symbols-A4.pdf. Very useful. – Steven B. Segletes Mar 20 '13 at 12:21
    
In addition to trying the above, could you perhaps draw what you want and upload it here? (Carefully drawing it on paper and then taking a picture is probably the easiest way.) Mathematical notation varies greatly from region to region; e.g. my training urges me to use something similar to \func. – Sean Allred Mar 20 '13 at 12:25
    
\stackrel{\frown}{=} – hpesoj626 Mar 20 '13 at 12:26
4  
Since you even linked to the Comprehensive LaTeX symbol list: Table 76, second column, last row on page 32 ;-) – mafp Mar 20 '13 at 12:32
3  
I addition to @mafp's command \mathrel{\widehat{=}} might help you. It would help us, if you discribe, what is not good with the commands you found. – Dominikus K. Mar 20 '13 at 12:35
up vote 7 down vote accepted

Try this. Of course, the parameters can be adjusted to change vertical separation height or horizontal width of wedge relative to = sign, or aspect ratio of wedge. Note that the appearance of this is not quite the same as \hateq cited in comments above, but better conforms to the symbol illustrated by the questioner.

REVISED SOLUTION eliminated use of array to make space around \equalhat compatible with \mathrel.

\documentclass{article}
\usepackage{scalerel,stackengine,amsmath}
\newcommand\equalhat{\mathrel{\stackon[1.5pt]{=}{\stretchto{%
    \scalerel*[\widthof{=}]{\wedge}{\rule{1ex}{3ex}}}{0.5ex}}}}
\begin{document}
\[
x^2 \equalhat \ensurestackMath{\Centerstack[c]{a b c}}
\]

\begin{align}
a &\equalhat b \\
a &= b
\end{align}
\end{document}

enter image description here

ORIGINAL SOLUTION

\documentclass{article}
\usepackage{scalerel,amssymb}

\newcommand\equalhat{%
\let\savearraystretch\arraystretch
\renewcommand\arraystretch{0.3}
\begin{array}{c}
\stretchto{
    \scalerel*[\widthof{=}]{\wedge}
    {\rule{1ex}{3ex}}%
}{0.5ex}\\ 
=%
\end{array}
\let\arraystretch\savearraystretch
}

\begin{document}

$x^2 \equalhat \begin{array}{c}a\\b\\c\end{array}$

\end{document}

enter image description here

share|improve this answer
    
What I don't like with this solution is that $a \equalhat b$ and $a = b$ have different spacing. Can this be fixed? – bers Feb 3 at 17:30
    
@bers That is a problem with the array environment, as I understand it. I will give thought to fixing that (after I get back from next meeting). – Steven B. Segletes Feb 3 at 17:58
    
@bers One quick and simple fix is to edit the \equalhat definition by adding a \! at the very beginning and very end of the definition. – Steven B. Segletes Feb 3 at 18:20
    
Sure, this work, but rather imperfectly (if what one is after is alignment with the regular = character). – bers Feb 3 at 18:34
    
@bers I am not sure that the quick fix is imperfect, but in any event, I have revised the solution to eliminate the use of array. – Steven B. Segletes Feb 3 at 19:12

Not the answer you're looking for? Browse other questions tagged or ask your own question.