Chapter 5, Class problem 2

Plot3D[
{(Sqrt[(x^2)+(y^2)])},
{x,-2,2},{y,-2,2},
ColorFunction->"Rainbow",
SphericalRegion->True,
AspectRatio->1,
AxesOrigin->{0,0,0},
ImageSize->600,
AxesStyle->Black,
Mesh->None,
RegionFunction->Function[{x,y,z},1≤(Sqrt[(x^2)+(y^2)])≤2],
PlotRange->{{-2.2,2.2},{-2.2,2.2},{0,2.2}}
]