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## Main Question or Discussion Point

If we define a set, c, to be R^2, how is it open and closed?

The definitions I'm using:

Open set: Open set, O, is an open set if for all points

Closed set: Compliment of an open set, AKA R^n/O.

This isn't a HW question, I'm reviewing the analysis part of my PDE course from fall semester, and this is something extra she told us, and now I don't know how this could be true!

Thanks for the help.

The definitions I'm using:

Open set: Open set, O, is an open set if for all points

__x__are in O, and we can find ONE B(x,ρ) such that B(__x__,ρ) is less than zero.Closed set: Compliment of an open set, AKA R^n/O.

This isn't a HW question, I'm reviewing the analysis part of my PDE course from fall semester, and this is something extra she told us, and now I don't know how this could be true!

Thanks for the help.

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