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Corollaries for Stokes' Theorem

COROLLARY 1

If f(x, y, z) has continuous second partials, then the line integral of grad f around the boundary of any oriented surface is zero,

13_vector_calculus-320.gif

(See Figure 13.6.3.)

13_vector_calculus-323.gif

Figure 13.6.3 

PROOF

curl(grad f) = 0,

so

13_vector_calculus-321.gif

COROLLARY 2

The surface integral of curl F over an oriented surface depends only on the boundary of the surface. That is, if ∂S1 = ∂S2 then

13_vector_calculus-322.gif

(See Figure 13.6.4.)

13_vector_calculus-324.gif

Figure 13.6.4

PROOF

By Stokes' Theorem, both surface integrals are equal to the line integral

13_vector_calculus-325.gif

For fluid flows, Stokes' Theorem states that the circulation of fluid around the boundary of an oriented surface S is equal to the surface integral of the curl over S.

We shall not prove Stokes' Theorem, but will illustrate it in the following examples.


Last Update: 2006-11-22