proving an intersection empty set


by rbzima
Tags: intersection, proving
rbzima
rbzima is offline
#1
Jan30-08, 06:10 PM
P: 86
I'm trying to prove

[tex]\bigcap^{\infty}_{n=1}(0,1/n) = [/tex] EMPTY SET.

One thing that I can't seem to bypass is getting past the closed intervals as stated in the Nested Interval Property, which states "For each [tex]n\in[/tex] N, assume we are given a closed interval [tex]I_n = [a_n, b_n] = {x \in[/tex] R [tex]: a_n \leq x \leq b_n}[/tex]. Assume also that each [tex]I_n[/tex] contains [tex]I_n_+_1[/tex].

Therefore, [tex]\bigcap^{\infty}_{n=1}I_n \neq [/tex] EMPTY SET.

Basically, I'm stuck at taking care of the open interval part of this proof. The original for R was proved by showing sup A = x, then x is between the closed interval. Any advice would be great!
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d_leet
d_leet is offline
#2
Jan31-08, 12:16 AM
P: 1,076
Obviously the intersection is a subset of (0,1), Why? So it will suffice to show that for any x in (0,1) that there exists a set of the form (0, 1/n) to which x does not belong. So basically given x in (0,1) can you figure out how to find n such that x does not belong to (0, 1/n)?


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