Art of Problem Solving

Well Ordering Principle: Difference between revisions

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The '''Well Ordering Principle''' states that every nonempty set of positive integers contains a smallest member.
The '''Well Ordering Principle''' states that every nonempty set of positive integers contains a smallest member. The proof of this is simply common sense, but we can construct a formal proof by contradiction. Assume there is no smallest element. Then for each element in the set, there exists a smaller element, so if we take this smaller element, there must a different smaller element, and so on. Since the set is finite, we cannot continue like this infinitely many times, contradiction.


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[[Category:Axioms]]
[[Category:Axioms]]

Revision as of 21:54, 14 July 2020

The Well Ordering Principle states that every nonempty set of positive integers contains a smallest member. The proof of this is simply common sense, but we can construct a formal proof by contradiction. Assume there is no smallest element. Then for each element in the set, there exists a smaller element, so if we take this smaller element, there must a different smaller element, and so on. Since the set is finite, we cannot continue like this infinitely many times, contradiction.

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