[Tex/LaTex] way to do an “upside down” \widehat

accentssymbols

I've come across this in a book I'm looking through, but I can't find the code for it. I want it to look exactly like the \widehat and go above text like \widehat does…I just want it to be (vertically) flipped!

Best Answer

The symbol you are looking for is widecheck and can be found in the mathabx font package. Please consult pages 10 and 16 of the mathabx user manual. The syntax is \widecheck{xyz}.

Here is a minimum working example to demonstrate:

enter image description here

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathabx}
\begin{document}
$\widecheck{\theta\tilde\theta} + \widecheck{\phi^2-\rho}$
\end{document}

The second example compares the behavior of \hat, \widehat, \check, and \widecheck.

enter image description here

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathabx}
\renewcommand\arraystretch{2.5}
\begin{document}
\begin{tabular}{|c|c|c|}
\hline 
& \textbf{narrow} & \textbf{wide} \\
\hline
\textbf{hat} & $\hat{I}+\hat{II}+\hat{III}+\hat{IIII}$ & $\widehat{I}+\widehat{II}+\widehat{III}+\widehat{IIII}$\\
\hline
\textbf{check} & $\check{I}+\check{II}+\check{III}+\check{IIII}$ & $\widecheck{I}+\widecheck{II}+\widecheck{III}+\widecheck{IIII}$\\
\hline
\end{tabular}
\end{document}

To install the mathabx font package, one of the following may work:

  1. If you are using Debian/Ubuntu, simply run sudo apt-get install texlive-fonts-extra texlive-fonts-extra-doc.
  2. If you have a new version of TexLive, then something like sudo tlmgr update --self followed by tlmgr install mathabx should work (I haven't tested this because I do not have tlmgr).
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