# Solid bounded by given region.

Posted 9 years ago
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 Why can't Wolfram do this: plot solid bounded by (z=0, z=4(?(X^2+y^2)), and (?(X^2+y^2))=2) ? Am I missing an app or widget somewhere? Please and thanks!
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Posted 9 years ago
 Am I missing an app or widget somewhere? No, what you're missing is called syntax, not widget RegionPlot3D[0 <= z >= 4 Sqrt[x^2 + y^2] && (x^2 + y^2) <= 4, {x, -2.1, 2.1}, {y, -2.1, 2.1}, {z, -.1, 8.1}, PlotPoints -> 35, PlotRange -> All, PlotStyle -> Directive[Yellow, Opacity[0.8]], PerformanceGoal -> "Quality"] 
Posted 9 years ago
 I am not quite sure I understand your constraints, but probably you want to use RegionPlot3D. Here is an example which may be close to yours: RegionPlot3D[ z > 0 && z < 4 Sqrt[x^2 + y^2] && z > 2 Sqrt[x^2 + y^2], {x, -10, 10}, {y, -10, 10}, {z, 0, 20}] Also ContourPlot3D can give some insight: ContourPlot3D[{z == 0, z == 4 Sqrt[x^2 + y^2], 2 == Sqrt[x^2 + y^2]}, {x, -10, 10}, {y, -10, 10}, {z, 0, 20}]