Is there a \widecheck like \widehat?

Question

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?

Answer 1

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.