A subset $S$ of $\Bbb R^n$ is Jordan measurable if and only if the measure of the set of its boundary points is zero. Basically I tried to imagine a set which has boundary points of nonzero measure, but I couldn't. Can you give me some examples? In my mind every boundary set of points of any set has zero measure.
2026-04-03 07:27:39.1775201259
Example of set which has a boundary of non-zero measure
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