What is the meaning of the symbol that looks like \ni in mathematics?

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Discussion Overview

The discussion centers around the interpretation and usage of a mathematical symbol resembling \ni, which some participants associate with the phrase "such that." The conversation explores its application in set builder notation and the potential confusion it may cause among students.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants mention that in set builder notation, \in typically means "in," while the vertical bar "|" is commonly used for "such that."
  • One participant expresses confusion regarding the use of \ni for "such that," suggesting it may lead to misunderstandings, as it resembles \in, which denotes membership.
  • Another participant notes that they were introduced to the notation during calculus but acknowledges that most people prefer using "s.t." instead.
  • A participant points out that the symbol for "such that" differs from the epsilon symbol in size, but they have not encountered it in standard mathematical texts.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness and clarity of using the \ni symbol for "such that." There is no consensus on its usage, with some finding it confusing while others do not.

Contextual Notes

There are unresolved questions regarding the notation's acceptance in mathematical literature and its potential for confusion among students.

futurebird
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My prof writes this symbol that looks (sort of) like this [tex]\ni[/tex] for "such that"

I just write the words "such that" in my notes...

But what is this symbol? I just choose the latex that looked most like what's on the board... is it the right one?
 
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Well in set builder notation usually [tex]\in[/tex] means "in" and "|" for "such that". Eg [tex]S=\{ k \in \mathbb{Q} | \sqrt{k} \in \mathbb{C} \}[/tex] means the set S is equal to the set of rational numbers such that sqrt k is a complex number.
 
futurebird said:
My prof writes this symbol that looks (sort of) like this [tex]\ni[/tex] for "such that"

I just write the words "such that" in my notes...

But what is this symbol? I just choose the latex that looked most like what's on the board... is it the right one?

I was introduced with this notation back when i started calculus. However most people use s.t rather than that.
 
futurebird said:
My prof writes this symbol that looks (sort of) like this [tex]\ni[/tex] for "such that"

I just write the words "such that" in my notes...

But what is this symbol? I just choose the latex that looked most like what's on the board... is it the right one?

I think that if your professor does use that symbol, then it's very confusing. As Gib Z says, [itex]\in[/itex] means a member of and so the backward version means exactly the same: e.g. [itex]\mathbb{N}\ni n[/itex].
 
leon1127 said:
I was introduced with this notation back when i started calculus. However most people use s.t rather than that.

Okay. I just wanted to know if anyone else had seen it. I don't find it that confusing... I wanted to know if this is what it looked like becuse my prof writes it in this odd way.
 
The symbol for "such that" and epsilon has a bit difference. The symbol is larger. But I haven't seen anything springer book using that symbol for such that.
 

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