#24

Show[Plot3D[x,{x,0,1},{y,0,2},RegionFunction->Function[{x,y,z},x<y<2-x],AxesLabel->{x,y,z},PlotRange->{0,1}],Plot3D[0,{x,-1,1},{y,0,1},RegionFunction->Function[{x,y,z},x<y<2-x],AxesLabel->{x,y,z},PlotRange->{0,1}]]

#32

Show[Plot3D[2+y,{x,-1,1},{y,0,1},RegionFunction->Function[{x,y,z},y>x^2],AxesLabel->{x,y,z},PlotRange->{0,3}],Plot3D[3y,{x,-1,1},{y,0,1},RegionFunction->Function[{x,y,z},y>x^2],AxesLabel->{x,y,z},PlotRange->{0,3}]]

Example 1

Plot3D[Exp[-x^2-y^2],{x,-2,2},{y,0,4},RegionFunction->Function[{x,y,z},0<y<Sqrt[4-x^2]],AxesLabel->{x,y,z}]