# Confused About Set Notation: A set of two variables is an element of the Cartesian square/product of a set of two numerical values?

I apologize if the title doesn't make sense, I am not fluent in the language of mathematics.

Suppose I have some arbitrary constant $$α>1.$$

Knowing just this, I am trying to interpret the meaning of $$(α,β)∈(0,1)^2$$

My first point of confusion is that I am not sure whether I am meant to view $$(α,β)$$ and $$(0,1)$$ as sets or as ordered pairs. To my understanding, sets are denoted with braces {x,y} whereas ordered pairs are denoted with parenthesis (x,y). Does the phrase "the ordered pair $$(α,β)$$ is an element of the ordered pair $$(0,1)^2$$" make any coherent sense? I assumed this was a mistake of notation, and I am actually trying to find {α,β}∈{0,1}$$^2$$

Secondly, assuming they are actually sets, I am confused about the relationship. Let the set A = {α,β} and the set B = {0,1}, such that $$A∈B^2$$.

I interpreted this to mean "the set A containing the elements $$α$$ and $$β$$ is an element of the Cartesian square of the set B containing the elements 0 and 1, given by the Cartesian product $$B^2 = B*B$$ = {(0,0),(0,1),(1,0),(1,1)} such that {α,β}$$∈$${(0,0),(0,1),(1,0),(1,1)}

But then I got stuck, since I am not sure how the set A containing two undetermined variables as elements can itself be an element of a set of ordered pairs.

Where am I going wrong here?

• $(\alpha,\beta)$ is an ordered pair; $(0,1)$ is the set of real number strictly between $0$ and $1$. Commented Oct 23, 2020 at 2:18
• $(0,1)^2$ is almost certainly the collection of all points $(x,y)$ with $0\lt x\lt 1$ and $0\lt y\lt 1$; this is the topological notation. And $(\alpha,\beta)$ is a point on the plane. So all it is telling you is that $(\alpha,\beta)$ is a point on the plane with $0\lt\alpha\lt 1$ and $0\lt \beta\lt 1$. Commented Oct 23, 2020 at 2:31

As with all ambiguous notation and language (which is to say, all notation and language), the interpretation depends on context. That said, the statement $$(\alpha,\beta)\in(0,1)^2$$ is very likely to mean that the ordered pair $$(\alpha,\beta)$$ is an element of the Cartesian product $$(0,1)\times (0,1)$$ where $$(0,1)$$ denotes the interval $$\{x\in\mathbb{R}:0 (not an ordered pair!). So in other words, $$(\alpha,\beta)\in(0,1)^2$$ just means $$0<\alpha<1$$ and $$0<\beta<1$$.
Of course, with your stated assumption that $$\alpha>1$$, this will never be true. So perhaps you are misunderstanding something about this assumption, or there is a typo somewhere, or this statement is just intended to be a false one.