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Results tagged with elementary-set-theory
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user 31
For elementary questions on set theory. Topics include intersections and unions, differences and complements, De Morgan's laws, Venn diagrams, relations and countability.
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Construct a bijection from $\mathbb{R}$ to $\mathbb{R}\setminus S$, where $S$ is countable
An explicit bijection $(0,1) \to [0,1]$ for part $1$ is given by:
$$f\left(\frac{1}{2}\right) = 0,\quad f\left(\frac{1}{3}\right) = 1,\quad f\left(\frac{1}{n}\right) = \frac{1}{n-2}\ \textrm{for}\ n …