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Homework Help: The cardinality of the set of irrational numbers

  1. Mar 15, 2012 #1
    1. The problem statement, all variables and given/known data
    Suppose [itex]\mathbb{Q},\mathbb{R}[/itex] are the set of all rational numbers and the set of all real numbers, respectively. Then what is [itex]|\mathbb{R} \backslash \mathbb{Q}|[/itex]?

    2. Relevant equations
    [itex]|\mathbb{Q}| = |\mathbb{Z^{+}}| < |P(\mathbb{Z^{+}})| = |\mathbb{R}|[/itex]

    3. The attempt at a solution
    I can prove the relevant equations by the method of cut and general concepts of functions and logic. But actually my understanding of cut construction for R is kinda poor. So should I revise this concept to know the cardinality of the set of irrational numbers? Or do I need to know extra stuff?
  2. jcsd
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