I opted to not use the template because this is a pretty general question. I am not understanding how to find out if a set is an open subset of a Euclidean space.(adsbygoogle = window.adsbygoogle || []).push({});

For example,

{(x,y) belongs R2 | x squared + y squared < 1}

The textbook is talking about open balls, greatly confusing me.

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# Homework Help: How to determine if a set is an open subset of a Euclidean space?

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