Consider the set The collection of subsets are The book says the one point set is not closed because its complement is not open. What is the complement of
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Originally Posted by dwsmith Consider the set The collection of subsets are The book says the one point set is not closed because its complement is not open. What is the complement of
Originally Posted by Plato But that isn't in topology.
Originally Posted by dwsmith But that isn't in topology. That is exactly the point. The complement of is not an open set, not in the topology. There because the complement of is not open means is not closed.