Question #101044
give an example of a choice function on the collection.

X = {{0.1},{2,3},{4,5}}
1
Expert's answer
2020-01-06T09:42:17-0500

Axiom of Choice.

Let XX be a collection of nonempty sets. Then we can choose a member from each set in that collection. In other words, there exists a function ff defined on XX with the property that, for each set SS in the collection, f(S)f(S) is a member of S.S.

The function ff is then called a choice function.

For example, if XX is the collection X={{0,1},{2,3},{4,5}}X =\{ \{{0,1\}} ,\{{2,3\}},\{{4,5\}}\}, then we can define ff quite easily: just let f(S)f(S) be the smallest member of S.S.

Then the function that assigns 0 to the set {0,1},\{{0,1\}}, 2 to {2,3},\{{2,3\}}, and 4 to {4,5}\{{4,5\}} is a choice function on X.



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Comments

Assignment Expert
06.01.20, 18:06

If the set is finite, then there is a finite number of choice functions over this set. It was also discussed at https://math.stackexchange.com/questions/2469459/count-the-number-of-choice-functions .

younus
06.01.20, 16:56

so how many choice function can we defined on the set X

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