# Fundamental theorem of calculus for surface integrals?

1. Dec 27, 2013

### Jhenrique

Hellow!

A simple question: if exist the fundamental theorem of calculus for line integrals not should exist too a fundamental theorem of calculus for surface integrals? I was searching about in google but I found nothing... What do you think? Such theorem make sense?

2. Dec 27, 2013

### Boorglar

Yes, there are similar theorems for surface integrals. Look up Stokes' Theorem, and also the Divergence Theorem.

Stokes' theorem says that the surface integral of the curl of a vector field on a surface in R^3 is equal to the line integral of the vector field on the boundary of the surface.

The Divergence theorem says that the triple integral of the divergence of a vector field in a volume in R^3 is equal to the flux of the vector field through the surface which bounds the volume.

http://en.wikipedia.org/wiki/Kelvin–Stokes_theorem
http://en.wikipedia.org/wiki/Divergence_theorem

3. Dec 27, 2013

### Jhenrique

I disagree. The divergence theorem connects a double integral of a closed surface with a triple integral, similarly, the rotational theorem connects a simple integral of a closed curve with a dobule integral. These concepts are different from the fundamental theorem of calculus...

4. Dec 27, 2013

### Number Nine

Actually, all are just special cases of Stokes' theorem. They are deeply related.

5. Dec 27, 2013

### Jhenrique

I disagree again. The divergence theorem is used to calculate a volume by means of a triple integral or by means of a double integral of a closed surface of this volume. The rotational theorem is used to calculate an area by means of a double integral or by means of a simple integral of a closed curve of this area.
The fundamental theorem of calculus for line integrals is a concept that relates to the independence of a path, similarly, the fundamental theorem of calculus for surface integrals should give an explanation for integrals independent of the surface of integration.

6. Dec 27, 2013

### Number Nine

They are, in fact, all just special cases of Stokes' theorem (i.e. they all follow immediately). If you want "independence of surfaces", let F be a C1 vector field and let S1 and S2 be surfaces with a common boundary B (with all of the usual assumptions). By the Kelvin-Stokes theorem, the surface integrals of the curl of F over S1 and S2 are equal to the line integral of F over B, and so are identical. The value of the surface integral depends only on the line integral around the boundary.

Last edited: Dec 27, 2013
7. Dec 27, 2013

### Jhenrique

The rotational theorem says:
or:
$$\oint \vec{f}\cdot d\vec{s}=\iint |\vec{\bigtriangledown}\times\vec{f}|\;\;dxdy$$

And the divergence theorem says:
or:
$$\iint\!\!\!\!\!\!\!\!\!\!\subset\!\supset \vec{f}\cdot d\vec{S}=\iiint |\vec{\bigtriangledown}\cdot \vec{f}|\;\;dxdydz$$

* Of course the two circulations below are equals, independent of the path of integration. And the same goes for the two fluxes below, they are equals, independent of the surface of integration.

But now I ask you. What all this have to do with the fundamental theorem of calculus?

8. Dec 27, 2013

### Number Nine

They are all special cases of Stokes' theorem, as I said. Stokes' theorem unifies not only the fundamental theorem of calculus, but almost every major result in vector calculus. The link above explains everything quite well. Stokes' theorem relates integrals over the boundary of a manifold (a generalization of a surface) to integrals over the manifold itself. A curve is a one dimensional manifold, and its boundary consists of points; Stokes' theorem implies the fundamental theorem of calculus/line integrals in this case. The boundary of a 2 dimensional manifold (a surface) is a curve; Stokes' theorem implies most of the results from vector calculus in this case.

Last edited: Dec 27, 2013
9. Dec 27, 2013

### Jhenrique

Hmmm, now I undertood, so so, because I don't know how make a exterior derivative. But, anyway, exist a geometric explanation for the fundamental theorem of calculus for surface integral, a geometric explanation analogous to t.f.c. for line integral?

10. Feb 5, 2014

### ibdsm

Stokes Theorem connects (n+1)-fold integrals over a region with n-fold integrals over the boundary of the region.

The fundamental theorem of calculus is the case n=0. (An integral over a discrete set is a sum - use counting measure)