I'm having trouble understanding how to find the boundary in the sense of boundary of a surface, as opposed to boundary in the sense of boundary of a point-set. From what my professor said, it seems as though for surface boundaries, you just stare at the surface and figure out its boundary, but there's got to be a formalized method for doing this.(adsbygoogle = window.adsbygoogle || []).push({});

For example, take the upper hemisphere of a sphere in 3 space. Its boundary according the the point-set definition of boundary is the entire surface; put another way, if the surface is thought of as a subset of R3, it has no interior.

But the "surface boundary" of the hemisphere is the circle defining its base, according to my professor. How did he reach this conclusion???

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# Boundary vs. Boundary

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