As the topics. Proving that $\partial P'\subset \partial P $ if and only in $P'\cap P^0 \subset P'^0$. I am not sure how to start
Proving that $\partial P'\subset \partial P $ if and only in $P'\cap P^0 \subset P'^0$
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general-topology
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2Just to check, $\partial$ is boundary, $'$ is derived set, you're using a superscript zero for interior, and the setting is an arbitrary topological space? – 2012-10-13
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0yup, the notation are defined in that way – 2012-10-13
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0Pick elements.. – 2012-10-13