# The $$\in$$ symbol

• Sep 3rd 2010, 06:07 PM
lilaziz1
The $$\in$$ symbol
I'm reading my calc chapters and I don't know what this sign means. I thought I post it in the pre-algebra & algebra section because the symbol has nothing to do with calc.

So I was wondering what the symbol is called and what it means. Here it is: $\displaystyle \in$

It is used in context like this: The Cartesian product $\displaystyle \Re x \Re x \Re = { (x, y, z) | z, y, z \in \Re }$ is the set of all ordered triples of real numbers and is denoted by $\displaystyle \Re^3$
• Sep 3rd 2010, 07:29 PM
mr fantastic
Quote:

Originally Posted by lilaziz1
I'm reading my calc chapters and I don't know what this sign means. I thought I post it in the pre-algebra & algebra section because the symbol has nothing to do with calc.

So I was wondering what the symbol is called and what it means. Here it is: $\displaystyle \in$

It is used in context like this: The Cartesian product $\displaystyle \Re x \Re x \Re = { (x, y, z) | z, y, z \in \Re }$ is the set of all ordered triples of real numbers and is denoted by $\displaystyle \Re^3$

It means 'is an element of'.
• Sep 3rd 2010, 08:39 PM
Prove It
Or, less formally, it means "in".

So $\displaystyle x \in \mathbf{R}$ means "$\displaystyle x$ is an element of the Real Numbers", or "$\displaystyle x$ is in the set of Real Numbers", or "$\displaystyle x$ is a Real Number"...