- #1
kingwinner
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Homework Statement
Consider sequence of real numbers.
Theorem: If a= sup S, then there exist a sequence xn E S such that xn ->a
Proof:
Take ε = 1/n and find xn E S such that 0 ≤ a - xn < 1/n.
Now show xn -> a.
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I am very very confused about this proof.
1) Why are they taking ε = 1/n? What motivates this?
2) It seems to me that n is simply a "subscript" of the sequence xn and it's a bit weird to talk about ε = 1/n. Is there any relationship between the "n" in ε = 1/n and the "n" in the sequence xn? Are they the SAME "n"?
3) In the proof, they say "find xn E S such that 0 ≤ a - xn < 1/n", but how do we know that such a thing even EXISTS?
4) At the end of the proof, they say "show xn -> a", but HOW??
Homework Equations
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The Attempt at a Solution
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Can someone please explain the proof in greater detail?
Any help is much appreciated! :)