# Math Help - Verifying Stokes' Theorem

1. ## Verifying Stokes' Theorem

Problem- Given the vector field F= <yx, 0, x>, calculate both $\oint_{\partial S}$Fds ​and $\iint_S$curl(F)•dS over the portion of the plane $\frac{x}{2}$+ $\frac{y}{3}$+ z = 1 where x, y, z > 0, oriented with an upward normal vector.

I took $\nabla$ x F to get <0, y-1, z> which I dotted with nG(x,y)= < $\frac{1}{2}$, $\frac{1}{3}$,1> of my parameterization of the plane G(x,y) = (x, y, 1-( $\frac{x}{2}$+ $\frac{y}{3}$ ) to get $\frac{y-1}{3}$ +z. I then computed $\int_0^1$ $\int_0^{3-3z}$ $\frac{y-1}{3}$ +z dy dz to get $\frac{1}{2}$ which I believe is correct.

My issue lies in finding $\oint_{\partial S}$Fds. I tried defining $\partial$S as the sum of a set of three parameterized line segments c1 c2 c3 in the xy-plane, however none have a z-component, so when I took F(c1)•c'1 , F(c2)•c'2, and F(c3)•c'3 they all ended up as <0, 0, 0>. I tried defining $\partial$S in the yz-plane, but I met the same <0, 0, 0> dot products, so $\oint_{\partial S}$Fds​ and all of the three scalar line integrals composing it equated to be 0. I feel like I'm doing something wrong.

Any help?
Thanks
Anthony

2. ## Re: Verifying Stokes' Theorem

Three parametrized line segments are indeed how you would break up the boundary of S. But one each lies in the xy-, xz-, and yz-planes. Try drawing a picture like the one I've added below.