How to use the negated approximate sign

Question

I'm trying to get the negated \approx sign in LaTeX, as it is in here:

enter image description here

But the \napprox command does not work. Any ideas? Maybe it was switched to a new command? Or do I just need to include some package?

Welcome to TeX.SX! You can have a look on our starter guide to familiarize yourself further with our format. — Marco Daniel, May 31 '13 at 14:52
Question solved, I've used the \not \approx, thanks Corentin! — EmeritusJr, May 31 '13 at 15:03
According to the Comprehensive LaTeX symbol lists, \napprox is defined by the mathabx package — jub0bs, May 31 '13 at 15:14
@EmeritusJr -- some history ... when amssymb was created, space was at a premium, so negated relations that looked (and behaved) okay using \not\xxx weren't included. you can make your life a little easier by making your own definition: \newcommand{\napprox}{\not\approx} — barbara beeton, May 31 '13 at 15:15

score 21 · Answer 1 · answered May 31 '13 at 15:14

The table you show is relative to the symbols provided by mathabx. One can say

\usepackage{mathabx}

but this will change many symbols and not always in a desirable way.

For negated relations one can first try preceding the command by \not:

\not\approx

The placement of the diagonal bar is not always ideal, which is why the negation of \in has its own command \notin. In the case of \not\approx there is no problem.

Here's a visual comparison: above the normal rendition of the symbol, using Computer Modern Math Symbols, below the mathabx rendition. A difference in shape is evident.

enter image description here

score 11 · Answer 2 · answered May 31 '13 at 16:40

11

Unless a font is used that contains the glyph ≉ (U+2249 NOT ALMOST EQUAL TO), the symbol is constructed by the two relational symbols \not and \approx. The appearance looks o.k., but the result from "copy & paste" is "suboptimal". This can be improved by package accsupp that uses the ActualText feature of PDF (for PDF viewers that support this feature such as Acrobat Reader):

\documentclass{article}
\usepackage{accsupp}
\providecommand*{\napprox}{%
  \BeginAccSupp{method=hex,unicode,ActualText=2249}%
  \not\approx
  \EndAccSupp{}%
}
\begin{document}
\[ a \napprox b \]
\end{document}

Result from "copy & paste" (AR9/Linux): a ≉ b

answered May 31 '13 at 16:40

Heiko Oberdiek

271,626

It's nice that \BeginAccSupp and \EndAccSupp don't add items to the math list, so the spacing is correct (tested with a binary operator). – egreg May 31 '13 at 18:06
@egreg Yes, just whatsits are inserted (\pdfliteral or \special), no boxes. And I prefer \begingroup ... \endgroup for grouping. Curly braces for grouping would interfere by adding a subformula. – Heiko Oberdiek May 31 '13 at 21:30

How to use the negated approximate sign

2 Answers2