quarto=RegionPlot[And[1≤x≤2,0≤y≤(Sqrt[1-(((x-1))^2)])],{x,0,2},{y,0,2},BoundaryStyle->{Blue,Thick},PlotPoints->30,GridLines->Automatic]

Show[quarto,Graphics[{Thick,Black,Dashed,Circle[{1,0},1,{π/2,π}]}]]

picanha=Plot3D[{0, (1/(Sqrt[(x^2)+(y^2)]))},{x,1,2},{y,0,1},RegionFunction->Function[{x,y,z},(((x-1))^2)+(y^2)≤1],Mesh->False,PlotStyle->{Opacity[0.3],Opacity[0.2]},BoundaryStyle->{{Blue,Thick},{Blue,Thick}},Filling->Bottom]

g[x_,y_]=(1/(Sqrt[(x^2)+(y^2)]));

fatia=ParametricPlot3D[{1.5,y,z},{y,0,(Sqrt[1-(((1.5-1))^2)])},{z,0,g[1.5,y]},Mesh->False,PlotStyle->{Yellow},BoundaryStyle->{Blue,Thick}];

Show[picanha,fatia]

Show[quarto,Graphics[{PointSize[Large],Black,Thick,Point[{{0,0},{1.5,(Sqrt[1-(((1.5-1))^2)])},{1,((Sqrt[1-(((1.5-1))^2)])/1.5)}}],Line[{{0,0},{1.5,(Sqrt[1-(((1.5-1))^2)])}}],Circle[{0,0},0.5,{0,ArcTan[((Sqrt[1-(((1.5-1))^2)])/1.5)]}],Text[Style["θ",Large],{0.6,0.1}],Text[Style["r1 = secθ",Large],{0.6,0.6}],Text[Style["r2 = 2cosθ",Large],{1.7,1}]}]]

AbsoluteTiming[Integrate[Integrate[1 ,{r, Sec[θ], 2Cos[θ]}],{θ,0,π/4}]]

cilindro=ParametricPlot3D[{2 Cos[θ],2 Sin[θ],z},{θ,0,2π},{z,0,2},PlotStyle->{Opacity[0.4],LightGray,Specularity[White,300]}]

inclisemi=ParametricPlot3D[{r Cos[θ],r Sin[θ],r Cos[θ]},{θ,-π/2,π/2},{r,0,2},PlotStyle->{Opacity[0.6],LightBlue,Specularity[White,300]}]

Show[cilindro,inclisemi]

esfera=ParametricPlot3D[{Cos[λ]Cos[ϕ],Cos[λ]Sin[ϕ],Sin[λ]},{λ,-π/2,π/2},{ϕ,-π,π},PlotStyle->{Opacity[0.4],LightGray,Specularity[White,300]}]

plano=Plot3D[1/2,{x,-1,1},{y,-1,1},MeshFunctions->(((#1)^2)+((#2)^2)&),Mesh->{{3/4}},PlotStyle->{Opacity[0.6],LightBlue,Specularity[White,300]},MeshStyle->{Black,Dashed,Thick}]

Show[esfera,plano]

Graphics3D[Sphere[{0,0,0},1]]

bicirc=Graphics[{{LightGreen,Disk[{0,0},1],Disk[{4,0},1]},{Dashed,Black,Thick,Circle[{0,0},1],Circle[{4,0},1],Line[{{2,-1},{2,1}}]}}];

Show[ContourPlot[{x==0,y==0},{x,-1,5},{y,-1,1},GridLines->Automatic,AspectRatio->Automatic],bicirc]

toro=ParametricPlot3D[{2,0,0}+{(2+Cos[λ])Cos[ϕ],(2+Cos[λ])Sin[ϕ],Sin[λ]},{ϕ,-π,π},{λ,-π,π}]