# left / right angle accent

Is there a LaTeX math package that provides "angle" accents?

For example, a "right angle accent" applied to "a" would look like this:

I produced this image using the COMBINING LEFT ANGLE ABOVE Unicode character, which however does not seem to work in XeLaTeX, and there isn't a COMBINING RIGHT ANGLE ABOVE character anyway.

If not, is there another recommendation to denote a lower / upper bound? I've seen the convention to use a "L"or "U" as sub- or superscripts, but don't like that.

• Would it be in math mode? – Bernard Apr 19 at 23:16

Maybe something like this?

\documentclass{article}
\usepackage{amsmath}
\usepackage{accents}
\begin{document}
$\accentset{\lnot}{a}$ or $\accentset{\lnot}{\text{a}}$
\end{document}


• In math mode, you probably want \mathrm{a} instead of \text{a}. With \text, the formatting of the surrounding text (such as italics or bold) bleeds through. – Davislor Apr 20 at 2:56
• @Davislor Thanks! Yes, that's true. However, we do not know yet what the OP want's in the end. Maybe they want \textbf{$\accentset{\lnot}{\text{a}}$wesome}. Another concern is that \accentset does not seem to cooperate with hyperref in sections and the like. – user194703 Apr 20 at 3:03

The right angle accent ◌̚ (U+031A) is \droang in unicode-math. The fonts XITS Math and STIX Two Math both have it, but its positioning with STIX Two is off.

\documentclass{book}
\usepackage{unicode-math}

\setmathfont{XITS Math}

\begin{document}
$$\droang{a}$$
\end{document}


You can combine the accent from XITS Math with any math font:

\documentclass{book}
\usepackage{unicode-math}

\defaultfontfeatures{Scale = MatchLowercase}
\setmathfont{Latin Modern Math}
\setmathfont[range=\droang]{XITS Math}

\begin{document}
$$\droang{a}$$
\end{document}


You can use, as suggested, accents. In case you also need the reverse shape, there are two ways: one is more efficient, using wasysym, but it has the defect that the symbol may not blend with \lnot (if the math font is not Computer Modern). The second solution uses the same symbol, but horizontally reflected, so it automatically blends.

\documentclass{article}
\usepackage{amsmath,accents}

\usepackage{wasysym} % for \invneg
\usepackage{graphicx} % for the homemade reflected symbol

\makeatletter
\DeclareRobustCommand{\blnot}{{\mathpalette\b@lnot\relax}}
\newcommand{\b@lnot}[2]{\reflectbox{$\m@th#1\lnot$}}
\makeatother

\begin{document}

$\accentset{\lnot}{a}+\accentset{\invneg}{a}$
$\accentset{\lnot}{a}+\accentset{\blnot}{a}$

\end{document}