Thread: carthesian product of two closed sets

1. carthesian product of two closed sets

I have a question, what is the set $[0,1]\times[0,1]$? What does it contain?

I know that, the unit interval is $[0,1]:=\{x\in\mathbb{R}|0\lex\le 1$ but then

$[0,1]\times [0,1]=\{(x,y)|0\le x\le 1,0\le y\le 1|x,y\in\mathbb{R}\}$ is this true?

but then we must have $[0,1]\times [0,1]\subset \mathbb{R}^2$

I was given the following set $A=\{(x,x)|x\in[0,1]\}$ what is it and what does it contain? is it just a set of open intervals of the real line?
or is it a diagonal of the unit square?

2. Re: carthesian product of two closed sets

Hey rayman.

You are correct with your definition of [0,1] x [0,1].

As for (x,x) x in [0,1] - Consider all the points that it forms (it will form a straight line with y = x where x is in [0,1]).

3. Re: carthesian product of two closed sets

thank you chiro!

4. Re: carthesian product of two closed sets

Geometrically, [0, 1]x [0, 1] is the square in the xy-plane with verticex (0, 0), (0, 1), (1, 1), and (1, 0). {(x, x)}, x in [0, 1], is the diagonal from (0, 0) to (1, 1).