Talk:Excision theorem

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"The theorem states that if the closure of U is contained in the interior of A, then U can be excised". Is this the closure of U in X, rather than A? I think it should be but didn't want to change it without checking. This makes a real difference since A is always closed in itself.

Yes - the closure of U in X, and the interior of A in X (the interior of A in A is again A).

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