Is the Nested Interval Theorem Flawed in My Textbook?

[pyfgcr]

The Nested interval theorem: If A_n = [a_n, b_n] is a sequence of closed intervals such that A_n+1 \subseteq A_n for all n \in N, then _{n \in n}\bigcapA = ∅.
I think of the case where a1=a2=...=an and b1=b2=...=bn for all n, hence every set A(n+1) will be the "subset" of A(n) and the intersection is the original closed interval. So I think the theorem in my textbook have some problem. Any correction for this ?

 

[micromass]

The Nested interval theorem: If A_n = [a_n, b_n] is a sequence of closed intervals such that A_n+1 \subseteq A_n for all n \in N, then _{n \in n}\bigcapA = ∅.
I think of the case where a1=a2=...=an and b1=b2=...=bn for all n, hence every set A(n+1) will be the "subset" of A(n) and the intersection is the original closed interval. So I think the theorem in my textbook have some problem. Any correction for this ?

It should be:
If A_n=[a_n,b_n] is a sequence of closed intervals such that A_{n+1}\subseteq A_n for all n\in\mathbb{N}, then \bigcap_{n\in \mathbb{N}}A_n \neq \emptyset.

 

[DonAntonio]

It should be:
If A_n=[a_n,b_n] is a sequence of closed intervals such that A_{n+1}\subseteq A_n for all n\in\mathbb{N}, then \bigcap_{n\in \mathbb{N}}A_n \neq \emptyset.

...and not only that: it must be also that \,b_n-a_n\xrightarrow[n\to\infty]{} 0\, , as \,A_n:=[n,\infty)\, would contradict.

DonAntonio

 

[Bacle2]

Or, more generally, a collection of nested sequence of sets in a complete metric space

with diameter approaching 0 as n-->00 .