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

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The symbol resembling \ni is used by some professors to denote "such that," although it can cause confusion since \in typically means "in." In set builder notation, the standard symbol for "such that" is often represented by a vertical bar "|". Many students prefer writing "such that" or using "s.t." instead of the symbol. The discussion highlights that while some find the use of \ni acceptable, it is not commonly found in textbooks. Overall, clarity in notation is emphasized as crucial for understanding mathematical expressions.
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My prof writes this symbol that looks (sort of) like this \ni 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 \in means "in" and "|" for "such that". Eg S=\{ k \in \mathbb{Q} | \sqrt{k} \in \mathbb{C} \} 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 \ni 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 \ni 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, \in means a member of and so the backward version means exactly the same: e.g. \mathbb{N}\ni n.
 
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.
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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