Cardinality of a uncountable set.

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Homework Help Overview

The problem involves demonstrating that the set of all sequences of 0's and 1's, denoted as S, is uncountable. This relates to concepts in set theory and cardinality.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss using proof by contradiction or establishing a bijective map between S and the real numbers. There is mention of Cantor's diagonal argument as a potential method for proving uncountability.

Discussion Status

Some participants express uncertainty about how to begin the proof, while others suggest methods and approaches that could be taken. There is a recognition of the classic nature of the problem and the potential for a productive discussion around the methods proposed.

Contextual Notes

Participants are encouraged to think independently before seeking external explanations or solutions, reflecting the forum's emphasis on learning through exploration.

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Homework Statement



Let S be the set consisting of all sequences of 0's and 1's.

S = {(a_1, a_2, a_3,...):a_n = 0 or 1 }

Show that S is uncountable.

Homework Equations





The Attempt at a Solution



I'm not sure where to start. I think I should either assume that S~N and use proof by contradiction. Or maybe I could show that S has the same cardinality with R which means there is a bijective map between those two. Both of them don't seem easy.
I would really appreciate it if anyone could show me where to start.
 
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R.P.F. said:

Homework Statement



Let S be the set consisting of all sequences of 0's and 1's.

S = {(a_1, a_2, a_3,...):a_n = 0 or 1 }

Show that S is uncountable.

Homework Equations


The Attempt at a Solution



I'm not sure where to start. I think I should either assume that S~N and use proof by contradiction. Or maybe I could show that S has the same cardinality with R which means there is a bijective map between those two. Both of them don't seem easy.
I would really appreciate it if anyone could show me where to start.

We can use the same classic approach as the one used for proving that the set of all real numbers is uncountable, namely, Cantor's diagonal argument. BWOC, suppose the set is countable. List all these sequences in some order. Then generate a sequence of your own by a method that excludes it from this list, thus arriving at a contradiction, i.e., proving S is uncountable.
 
Here, I even found a decent explanation of this method. However, before you click the following link, please try and think of such a method by yourself. Just imagine how great you'll feel afterwards if you get it all by yourself!

http://en.wikipedia.org/wiki/Cantor's_diagonal_argument[/SPOILER]
 
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Thanks a lot! I know how to do this now! :)
 

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