Green's identities are a set of three vector derivative/integral identities which can be derived starting with the vector derivative identities
(1)
|
and
(2)
|
where
is the divergence,
is the gradient,
is the Laplacian, and
is the dot
product. From the divergence theorem,
(3)
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(4)
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This is Green's first identity.
(5)
|
Therefore,
(6)
|
This is Green's second identity.
Let
have continuous first partial derivatives and
be harmonic inside the region of integration.
Then Green's third identity is
(7)
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(Kaplan 1991, p. 361).