How can I write a reflected \sqrt operator?

Question

How can I produce this symbol in LaTeX? It is used in Galois theory for p-adic fields to denote a root of the equation X^{p}-X-a with a \in k, and being k a p-adic field. I have tried a lot of different things like rotatebox or reflect box, but I can't produce the same output.

Welcome to TeX SX! Are p and a part of the symbol (what does it denote, by the way)? — Bernard, Aug 22 '17 at 15:07
If I could obtain a command (for instance named "modified") and obtain the output writing \modified[p]{a} it would be nice, but it doesn´t matter really, I only need to obtain the same output. — matemagreek, Aug 22 '17 at 15:10
It´s usually used in Galois theory of p-adic field, to denote a rooth of the equation $X^{p}-X-a$ with $a\in k$, and being $k$ a $p$-adic field. — matemagreek, Aug 22 '17 at 15:11
Will a always be a single letter or may it be a longer expression? — Bernard, Aug 22 '17 at 15:16
if this is an "accepted" symbol (i.e., it has appeared in a publication reviewed for mathscinet), and you can provide a citation of where it appears, i can submit it to be considered for inclusion in unicode. the best documentation shows the symbol in a context that clarifies its meaning and usage. — barbara beeton, Aug 22 '17 at 18:53

score 26 · Answer 1 · answered Aug 22 '17 at 15:22

26

\documentclass{article}
\usepackage{graphicx}
\newcommand\reflectsqrt[2][\relax]{
  \ifx\relax#1
    \scalebox{1}[-1]{$\sqrt{\scalebox{1}[-1]{$#2$}}$}
  \else
    \scalebox{1}[-1]{$\sqrt[{\scalebox{1}[-1]{%
      \raisebox{-4pt}{$\scriptscriptstyle#1$}}}]{\scalebox{1}[-1]{$#2$}}$}
  \fi
}
\begin{document}
$x\reflectsqrt{a}$

$x\reflectsqrt[p]{a_3 + b^3}$
\end{document}

answered Aug 22 '17 at 15:22

Steven B. Segletes

237,551

2

@matemagreek please accept the answer if you think it solved your problem :-) – johk95 Aug 22 '17 at 15:53
It even works with $\reflectsqrt[p]{\frac{x}{y+1}}$ – Steven B. Segletes Aug 22 '17 at 16:16
I think using \ifx #1\relax is a little safer than \ifx\relax #1. – Werner Aug 24 '17 at 22:29
@Werner Why would that be? I am always reminded that doing an if-test using #1 first allows for false positives if, for example, #1 is specified as 11. – Steven B. Segletes Aug 29 '17 at 02:00
@StevenB.Segletes: True. I think best would be to use one of the techniques in How to check if a macro value is empty or will not create text with plain TeX conditionals? or What's the best practice way to test whether parameter is empty? – Werner Aug 29 '17 at 15:31
@Werner I see my test along the vein of (but not quite the same as)\if\relax\detokenize{#1}\relax. In my flavor of the test, the only failure I see is if the optional argument is a macro whose expansion begins with \relax. I'm still trying to imagine a valid invocation scenario where that actually could occur... – Steven B. Segletes Aug 29 '17 at 15:44
@Werner Perhaps Heiko's example of \ifx\TestEmptyFence#1\TestEmptyFence would be best... – Steven B. Segletes Aug 29 '17 at 15:46
@samcarter I used the same double-reflection trick here, except about the vertical axis: https://tex.stackexchange.com/questions/334813/how-to-create-a-backslash-fraction – Steven B. Segletes Sep 18 '17 at 17:23
@StevenB.Segletes I would upvote your other answer if I had not already done so :) – samcarter_is_at_topanswers.xyz Sep 18 '17 at 18:33

Bernard · Answer 2 · 2017-08-22T16:22:01.157

6

With stackengine:

\documentclass{article}

\usepackage{stackengine}
\newlength\rlength

\newcommand\padicroot[2]{\settowidth{\rlength}{\ensuremath{\,#2}}%
\stackMath\stackinset{c}{}{c}{-1.3ex}{\scriptscriptstyle#1}%
{\raisebox{-0.6ex}{\Large$\wedge$}}\mkern-2mu\rlap{\rule[-0.68ex]{\rlength}{0.5pt}}%
\mkern1mu#2}

\begin{document}

\[ \padicroot{p}{y} \]%

\end{document}

edited Aug 22 '17 at 16:22

answered Aug 22 '17 at 16:01

Bernard

271,350

2

Hoist by my own petard! +1 – Steven B. Segletes Aug 22 '17 at 16:02
I must say I was surprised you didn't use your own package ;o) I also thought of a solution like yours, but finally opted for this one as more flexible. – Bernard Aug 22 '17 at 16:07
You should edit your answer so that it does not require rightward scrolling. Just sayin' – Steven B. Segletes Aug 22 '17 at 16:14

How can I write a reflected \sqrt operator?

2 Answers2