Infinite Subsets: Length & Terms Explained

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Homework Help Overview

The discussion revolves around the properties of infinite subsets of the real numbers, particularly focusing on the relationship between the number of terms in a set and its length. Participants explore whether an infinite subset necessarily implies an infinite length or if it can have a finite length despite containing infinitely many elements.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants question the implications of a set being infinite, discussing examples such as the Cantor set and its properties in relation to length and cardinality.

Discussion Status

The discussion is active, with participants providing examples and counterexamples to clarify their points. Some guidance has been offered regarding the nature of infinite sets, but no consensus has been reached on the implications of these properties.

Contextual Notes

There is an ongoing exploration of definitions related to length and terms in infinite sets, with references to specific examples that challenge initial assumptions. The conversation reflects a mix of perspectives on the topic.

jason177
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Alright this is a pretty simple question. So if A is a infinite subset of the reals, does that mean that its length is infinite (eg. the set of all numbers from 0 to infinite) or could it also be just a set with an infinite number of terms (eg. the set of all real numbers between 1 and 2)?
 
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jason177 said:
Alright this is a pretty simple question. So if A is a infinite subset of the reals, does that mean that its length is infinite (eg. the set of all numbers from 0 to infinite)
No.
or could it also be just a set with an infinite number of terms (eg. the set of all real numbers between 1 and 2)?
Yes.In fact its length could be zero.
 
jason177 said:
Alright this is a pretty simple question. So if A is a infinite subset of the reals, does that mean that its length is infinite (eg. the set of all numbers from 0 to infinite) or could it also be just a set with an infinite number of terms (eg. the set of all real numbers between 1 and 2)?

Everyone's favorite counter example to everything: The Cantor Set.

Let C be the Cantor set. C is a subset of the unit interval. After you remove C from the unit interval, the length of what is left in the unit interval is 1, so the length of C is 0. At the same time, there are the same number of points in C as there are left in the unit interval, so C is infinite. C is an odd little set, you should check it out.
 
alright, thank you both for your replies
 

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