# Is there a \widecheck like \widehat?

I read that we can get the function of "widecheck" by importing the \widecheck command from the mathabx (Is there a way to do an "upside down" \widehat?), but I do not want to do that since I do not want to change the font style.

Can we define \widecheck by ourselves?

I did not know if it would be this easy, but it turned out so. I took my revised answer at Really wide hat symbol for \reallywidehat and made two simple changes:

1. I changed all occurences of "hat" to "check"

2. I changed the final \stackon argument from \tmpbox to \scalebox{-1}{\tmpbox}.

That was it. Here it is:

\documentclass{article}
\usepackage{scalerel,stackengine}
\stackMath
\newcommand\reallywidecheck[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}{\scalebox{-1}{\tmpbox}}%
}
\parskip 1ex
\begin{document}

$\reallywidecheck{zbcdefghijklm}$

$\reallywidecheck{zbcdefghijk}$

$\reallywidecheck{zbcdefghi}$

$\reallywidecheck{zbcdefg}$

$\reallywidecheck{zbcde}$

$\reallywidecheck{zbc}$

$\reallywidecheck{zb}$

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

\end{document}


Best of all, it avoids the use of mathabx, which resets a lot of math symbols.

• I've copied/pasted your code, and everything seems to be working nicely for the most part, but when I try to typeset and expression like "\reallywidehat{\chi}" it gives me an error that I'm missing a $. It only seems to work with Roman letters. What can I do to fix this issue? – Patch Aug 19 '19 at 3:04 • @Patch When I take my above code and add the line, $\reallywidecheck{\chi}\$, it works just fine. Remember, \chi is a math symbol and has to be invoked in math mode. – Steven B. Segletes Aug 19 '19 at 3:48
• Yeah, it wasn't working for me even in the dollar signs. I can't figure it out. I ended up just copy/pasting the segment of "widecheck" code directly from mathabx. I didn't need a "really" wide one after all. – Patch Aug 19 '19 at 4:07
• @Patch Make sure your package is up to date: scalerel 2016/12/29 v1.8 – Steven B. Segletes Aug 19 '19 at 4:17