Cantor's theorem: Difference between revisions

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better shortdesc
Fizykz (talk | contribs)
Changed order of reasons for contradiction to clarify. This is a more logical order as it's clear to see xi cannot be in f(xi) to get B at first glance, then leading to the next contradictory statement.
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Equivalently, and slightly more formally, we just proved that the existence of ξ ∈ ''A'' such that ''f''(ξ) = ''B'' implies the following [[contradiction]]:
:<math>\begin{aligned}
\xi \innotin f(\xi) &\iff \xi \in B && \text{(by assumptiondefinition thatof }f(\xi)=B\text{)}; \\
\xi \in B &\iff \xi \notinin f(\xi) && \text{(by definitionassumption ofthat }f(\xi)=B\text{)}.; \\
 
\end{aligned}</math>