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Verify that the Divergence Theorem is true for the vector field F on the region E.?
F = <x^2, -y, z>
E is the solid cylinder y^2 + z^2 < 9, 0<x<2
F = <x^2, -y, z>
E is the solid cylinder y^2 + z^2 < 9, 0<x<2
1 Answer
- ?Lv 76 years agoFavorite Answer
∫∫ F⋅ dS = ∫∫∫ div F dV
div F = x
∫∫∫ x dx dy dz
convert to cylindrical
y = r cos t
z = r sin t
x = x
dx dy dz = r dx dr dt
∫[0,2pi] ∫[0,3]∫[0,2] xr dx dr dt
1/2 (2^2)(1/2)(3^2)(2pi)
18 pi
∫∫ F⋅ dS
this has to be done in three pieces. The wall of the cylinder, and the top and bottom.
The bottom
x = 0
∫∫ <0,-y,z><-1,0,0> dy dz
∫∫ 0 dy dz
0
top cap.
∫∫ <2,-y,z><1,0,0> dy dz
∫∫ 2 dy dz
18 pi
about the wall
y = 3 cos t
z = 3 sin t
x = x
dS = <dx/dt,dy/dt,dz/dt>x<dx/dx,dy/dx,dz/dx>
<0, -3 sin t, 3 cos t>X<1,0,0>
<0,3sin t, 3 cos t>
∫ <x^2, -3 cos t, 3 sin t>⋅<0,3sin t, 3 cos t> dx dt
∫ 0 dx dt
0
18pi = 18 pi