How to Prove the Cardinality of Unions of Infinite Sets?

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SUMMARY

The union of c sets, each with cardinality c, also has cardinality c. This conclusion is established by demonstrating a bijection between the union of c intervals and the set of real numbers, specifically \(\mathbb{R}^2\). The discussion highlights the importance of understanding one-to-one and onto functions in proving this concept. The participant successfully navigates the complexities of infinite sets and cardinality through the use of mathematical mappings.

PREREQUISITES
  • Understanding of cardinality in set theory
  • Familiarity with bijective functions
  • Knowledge of real number properties and \(\mathbb{R}^2\)
  • Concept of countable and uncountable sets
NEXT STEPS
  • Study the properties of cardinality in set theory
  • Learn about bijections and their applications in mathematics
  • Explore the concept of countable unions of sets
  • Investigate the relationship between \(\mathbb{R}\) and \(\mathbb{R}^2\)
USEFUL FOR

Mathematicians, students of set theory, and anyone interested in the foundations of infinite sets and cardinality.

mufq15
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Homework Statement


Prove that the union of c sets of cardinality c has cardinality c.


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The Attempt at a Solution


Well, I could look for a one-to-one and onto function... maybe mapping the union of c intervaks to the reals, or something? I know how to demonstrate that a countable union of countable sets is countable, by showing how to label them.
I'm having a hard time with this one, though.
 
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[tex]\mathbb{R}^2 = \bigcup _{r \in \mathbb{R}} (\mathbb{R} \times \{ r\} )[/tex]

This should give you an easy way to associate a c-union of c-sets with R2. Now all you need is a bijection between R and R2.
 
Ohh, I think I finally get it! (after thinking about it for a loong while...) Infinity is hard for me to wrap my head around. Thanks a lot for your help.
 

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