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Can anyone explain the underlined part in green. I know what green's identity is it's just I don't understand why we are summing over the surfaces of the holes.

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usainlightning
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1 Answers1

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The boundary of $V$ consists of $S_0,S_1,...,S_N$, although you need to be somewhat careful about orientation here. Does that answer your question?

Steven Gubkin
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