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**Indexed Collection of Sets ... :(((**

My notes are confusing me so bad, worst part is that we're not using our book till later on and that just kills me a lot. I'm very text-book because notes never make sense to me.

Let [tex]A_n=[0,n][/tex]

a) What numbers are in [tex]\bigcup_{n=1}^{\infty}A_n[/tex]?

b) What numbers are in [tex]\bigcap_{n=1}^{\infty}A_n[/tex]?

Ok, so I have an example here ...

If

[tex]I=\{1,2,3...\}[/tex]

[tex]A_i=[-i,i][/tex]

Then

[tex]\bigcup=\mathbb{R}[/tex]

[tex]\bigcap=[-1,1][/tex]

I honestly, can't remember how we got [-1,1]???

a) Since An goes from 0 to n, wouldn't that make [tex]\bigcup=[0,\infty)[/tex]???