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Math Help - Countable Principle of Choice

  1. #1
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    Countable Principle of Choice

    Prove, using the Countable Principle of Choice, that every countable subset of \omega_1 has an upper bound in \omega_1.

    Notation: \omega_1 denotes the first uncountable ordinal.
    Last edited by selenne431; March 6th 2010 at 04:28 PM.
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  2. #2
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    Hi

    Hint: With the countable principle of choice, a countable union of countable sets is also countable.
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