I found this maths operator in Unicode:
⋇
It is called "Division Times" (U+22C7).
Does it behave like ±? For example: 3 ± 2 means it is an ∈ {1, 5}. So 3 ⋇ 2 means it is an ∈ {1.5, 6}?
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3First time i hear of this "operator". Not a standard one. I wonder why this made into Unicode... – lhf Jul 16 '16 at 13:29
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Idly I wonder if there is a LaTeX command for this. – quid Jul 16 '16 at 13:44
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1@quid: Detexify doesn't seem to know it. – hmakholm left over Monica Jul 16 '16 at 13:48
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It's been in Unicode since the first version of the Unicode Character Database (version 1.1.5, July 1995). Digging up a rationale for it may be difficult. – hmakholm left over Monica Jul 16 '16 at 13:50
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Why edit my my element of symbols into "is an element of"? – alan2here Jul 16 '16 at 14:05
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Your = ∈ is not a well-formed expression. It does not mean anything. – quid Jul 16 '16 at 14:09
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@HenningMakholm thanks for that information. I asked it on [tex.se] – quid Jul 16 '16 at 14:10
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"is equal to a member of" using symbols instead of words seemed reasonable. I have changed it back to something similar to your edit @quid – alan2here Jul 16 '16 at 14:19
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The version with just $\in$ is alright. I feel it is slightly less precise than the earlier version, but then I am biased. :-) I understood that was what you meant but one must not use = in that way. – quid Jul 16 '16 at 14:19
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Unicode characters do not "behave". Your semantic interpretation of them "behaves". – Kaz Jul 16 '16 at 16:16
2 Answers
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The intent ought to be what you said. So, it is $a ⋇ b$ is short for "$a \ b$ or $a \ b^{-1}$" that is the multiplicative analogue of $\pm$.
Yet, a more common way to write $a ⋇ b$ is just $a \ b^{\pm 1}$.
In addition, I never heard of this operator, all the early search hits are for Unicode-tables not math, and at least to me it looks quite similar to an asterisks at small font size.
In short, it seems more like an artifact of getting a symbol-set somehow 'complete.' Rather than something that is actually used.
That said, I just learned that there is a LaTeX (needs amssymb) and also MatjJax command for it, it is \divideontimes giving $\divideontimes$
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This answer won, but both answers are good and appreciated. I wish there was a feature to combine similar answers into one answer. – alan2here Jul 16 '16 at 14:35
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Coincidentally, I saw it appear yesterday in Go Yamashita's notes on inter-universal Teichmüller theory, and while I'm not sure, I imagine it didn't mean anything like what you said. – MJD Jul 16 '16 at 16:18
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@MJD that's amazing. I just checked some of the slides. I actually think it is used roughly with about those semantics though. Well, it is not even used as a binary operator, but rather as a superscript. Yet it does appear to indicate that elements and their multiplicative inverses are identified. – quid Jul 16 '16 at 17:48
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No, it doesn't behave like $\pm$. An important part of how $\pm$ behaves is that it is likely to be understood without further explanation, and the $⋇$ sign does not have that property.
You can use it for "divided or multiplied by" if you want, but you will have to explain this usage to your reader before you do so, because you can't expect it to be clear that is what you want.
I would expect it is most likely to be used when someone needs a symbol for a new thing that behaves syntactically like a multiplication-like operator but is not actual multiplication -- and there is reason not to use the more common choices such as $*$, $\star$, $\otimes$, $\circledast$, and so forth.
hmakholm left over Monica
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1Downvoted because the lede here is simply neither tenable nor persuasive. I introduce a legion of community college students to the plus-or-minus every semester, and the majority are uniformly confused, baffled, and desperate for an explanation. Just like any notation someone hasn't seen before. – Daniel R. Collins Jul 16 '16 at 18:08
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2@DanielR.Collins Sure, but any paper using ± can rely on much of its audience being part of the legions of students that have been introduced to it. Sure, everything has to be introduced some time - you had to learn + and − themselves in primary school, after all. But ⋇ is never introduced to any general population of students at all. – Random832 Jul 16 '16 at 18:21
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@DanielR.Collins, how did people get to a college without having seen the quadratic formula? Even the Wikipedia entry on it mentions the ± symbol. – Bolpat Jul 11 '23 at 11:36
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@QuirinF.Schroll: That level of math (Algebra II) isn't required to graduate a U.S. high school. It's not even required to graduate from college (U.S. 2-year degree). – Daniel R. Collins Jul 11 '23 at 13:56
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@DanielR.Collins, really? You sure, we talk about the same thing, the solutions for x² + a x + b = 0? That’s baffling. – Bolpat Jul 12 '23 at 17:57
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As an example I'll cite the CUNY Elementary Algebra Final Exam, which was previously a base-level requirement to graduate with a CUNY 2-year college degree. Note the quadratic formula isn't required in that curriculum (e.g., see question #17). I say was because even this level of algebra requirement was removed as of last year. https://www.cuny.edu/wp-content/uploads/sites/4/page-assets/academics/testing/Sample-CEAFE-D-1.pdf – Daniel R. Collins Jul 12 '23 at 19:17
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... and to relate directly to this question, note that the $\pm$ symbol appears no place in that final exam. – Daniel R. Collins Jul 12 '23 at 19:19