Infinite Subsets: Length & Terms Explained

In summary, A infinite subset of the reals can have either an infinite length, such as the set of all real numbers from 0 to infinite, or it can have a finite length of 0, such as the Cantor Set. It can also have an infinite number of terms, as seen in the Cantor Set. This example highlights the complexity of infinite subsets and the importance of considering all possibilities.
  • #1
jason177
27
0
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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  • #2
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.
 
  • #3
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.
 
  • #4
alright, thank you both for your replies
 

1. What is an infinite subset?

An infinite subset is a subset of a set that has an infinite number of elements. It is a part of a larger set, but it contains an endless number of objects.

2. How is the length of an infinite subset determined?

The length of an infinite subset is determined by the number of elements it contains. Since an infinite subset has an uncountable number of elements, its length is considered infinite.

3. Can an infinite subset have a finite length?

No, an infinite subset cannot have a finite length. By definition, an infinite subset has an infinite number of elements, so its length is always considered infinite.

4. What are the terms used to describe infinite subsets?

The terms used to describe infinite subsets include "infinite", "uncountable", "unbounded", and "endless". These terms emphasize the never-ending nature of infinite subsets.

5. How are infinite subsets used in mathematics and science?

Infinite subsets are used in various areas of mathematics and science, such as set theory, calculus, and physics. They allow for the exploration of infinite concepts and help to solve complex problems involving infinite quantities.

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