Really wide hat symbol

Question

Is there any way to get a hat wider than widehat?

Why doesn't

\widehat{abcdefghijklmnopqrstuvwxyz}

really go over all of it?

Answer 1

The question wasn't "should it be done?" But, for the same reason men climb mountains, "could it be done?" The answer, with the scalerel package, is yes. Thus, we introduce \reallywidehat [EDITED to add phantom rule below argument, so that baseline of result matches baseline of original argument. RE-EDITED to \ensuremath on the \widthof calculation (thanks to Thruston)]

See also my answer at Serious problem with \widebar for a related approach.

NEW ANSWER WITH stackengine

This answer is an improvement because it handles vertical space much better than the earlier solution.

\documentclass{article}
\usepackage{scalerel,stackengine}
\stackMath
\newcommand\reallywidehat[1]{%
\savestack{\tmpbox}{\stretchto{%
  \scaleto{%
    \scalerel*[\widthof{\ensuremath{#1}}]{\kern-.6pt\bigwedge\kern-.6pt}%
    {\rule[-\textheight/2]{1ex}{\textheight}}%WIDTH-LIMITED BIG WEDGE
  }{\textheight}% 
}{0.5ex}}%
\stackon[1pt]{#1}{\tmpbox}%
}
\parskip 1ex
\begin{document}

$\reallywidehat{zbcdefghijklm}$

$\reallywidehat{zbcdefghijk}$

$\reallywidehat{zbcdefghi}$

$\reallywidehat{zbcdefg}$

$\reallywidehat{zbcde}$

$\reallywidehat{zbc}$

$\reallywidehat{zb}$

$x\cdot\reallywidehat{a_1+a_2}\cdot y$

\end{document}

ALTERNATE ANSWER USING \mathchar"0362 (the \widehat accent) RATHER THAN \bigwedge

EDITED to use \mathchar"0362 rather than the normal carat accent (\mathchar"305E)

A comment requested this alternate form, which is perhaps superior to the given form above.

\documentclass{article}
\usepackage{scalerel,stackengine}
\stackMath
\newcommand\reallywidehat[1]{%
\savestack{\tmpbox}{\stretchto{%
  \scaleto{%
    \scalerel*[\widthof{\ensuremath{#1}}]{\kern.1pt\mathchar"0362\kern.1pt}%
    {\rule{0ex}{\textheight}}%WIDTH-LIMITED CIRCUMFLEX
  }{\textheight}% 
}{2.4ex}}%
\stackon[-6.9pt]{#1}{\tmpbox}%
}
\parskip 1ex
\begin{document}

$\reallywidehat{zbcdefghijklm}$

$\reallywidehat{zbcdefghijk}$

$\reallywidehat{zbcdefghi}$

$\reallywidehat{zbcdefg}$

$\reallywidehat{zbcde}$

$\reallywidehat{zbc}$

$\reallywidehat{zb}$

$x\cdot\reallywidehat{a_1+a_2}\cdot y$

$\widehat{zb}$ is actual widehat

\end{document}

EARLIER ANSWER WITH array

\documentclass{article}
\usepackage{scalerel}

\newcommand\reallywidehat[1]{\arraycolsep=0pt\relax%
\begin{array}{c}
\stretchto{
  \scaleto{
    \scalerel*[\widthof{\ensuremath{#1}}]{\kern-.5pt\bigwedge\kern-.5pt}
    {\rule[-\textheight/2]{1ex}{\textheight}} %WIDTH-LIMITED BIG WEDGE
  }{\textheight} % 
}{0.5ex}\\           % THIS SQUEEZES THE WEDGE TO 0.5ex HEIGHT
#1\\                 % THIS STACKS THE WEDGE ATOP THE ARGUMENT
\rule{-1ex}{0ex}
\end{array}
}

\begin{document}

$\reallywidehat{zbcdefghijklm}$

$\reallywidehat{zbcdefghijk}$

$\reallywidehat{zbcdefghi}$

$\reallywidehat{zbcdefg}$

$\reallywidehat{zbcde}$

$\reallywidehat{zbc}$

$\reallywidehat{zb}$

$x\cdot\reallywidehat{a_1+a_2}\cdot y$

\end{document}

Answer 2

While echoing the sentiment expressed in the earlier answer -- "this stuff really shouldn't be encouraged" -- I can't resist pointing out that \widehat can easily be made super-wide with the help of the mtpro2 (MathTime Professional II) package. Note that this package isn't free of charge and can't be downloaded from the CTAN. However, its "lite" subset -- which is all that's needed to create superwide "widehat" accents -- is free of charge and may be downloaded from this site.

\documentclass{article}
\usepackage[lite]{mtpro2}
\begin{document}
$ \widehat{abcdefghijklmnopqrstuvwxyz} $
\end{document}

Answer 3

I tried some of these except the {mtpro2} since for submitting articles that might not be acceptable by publishers!

As I was not satisfied by the previous methods mentioned above, I tried to tailor another method, you can apply the following code, play with the scale factors and positions and choose which one you prefer. The last two I recommend but I myself prefer the last, which I am going to use myself:

\documentclass{article}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[ngerman]{babel}
\usepackage{stackengine}
\usepackage{scalerel}

\begin{document}

\[\widehat{ABCDEF}\]

\[\stackon[0pt]{ABCDEF}{\hstretch{7.0}{\wedge}}\]

\[\stackon[-8pt]{ABCDEF}{\vstretch{1.5}{\hstretch{9.0}{\widehat{\phantom{\;}}}}}\] 

\[\stackon[-8pt]{ABCDEF}{\vstretch{1.5}{\hstretch{2.4}{\widehat{\phantom{\;\;\;\;\;\;\;\;}}}}}\] 

\end{document}

The result would be something like this:

Have fun

Ehsan Tavakoli