# Wierd symbol what is it?

1. Nov 1, 2007

### futurebird

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?

2. Nov 2, 2007

### Gib Z

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.

3. Nov 2, 2007

### leon1127

I was introduced with this notation back when i started calculus. However most people use s.t rather than that.

4. Nov 2, 2007

### cristo

Staff Emeritus
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. $\mathbb{N}\ni n$.

5. Nov 2, 2007

### futurebird

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.

6. Nov 2, 2007

### leon1127

The symbol for "such that" and epsilon has a bit difference. The symbol is larger. But I havent seen anything springer book using that symbol for such that.