How can I plot a set of points in 3d?












0












$begingroup$


durnig exams I often have the problem to visualize the sets I should work with, especially in 3D. So I wanted to ask if there is a trick on how to sketch the following set for example



$ G:={(x,y,z)^T in mathbb{R}^3: x^2+y^2<4,~0<z<4-x^2-y^2} $



I would also really like to know how I could plot this by using WolframAlpha?










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  • $begingroup$
    It seems off-topic to ask about 3D plotting using WolframAlpha, though I can imagine having access to it during exams would simplify a large number of tasks. In general there is no trick to visualizing 3D sets using pencil and paper, or rather the approaches (isometric drawing and orthographic projection) are reasonably well-known but not taught specifically in math courses.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:05
















0












$begingroup$


durnig exams I often have the problem to visualize the sets I should work with, especially in 3D. So I wanted to ask if there is a trick on how to sketch the following set for example



$ G:={(x,y,z)^T in mathbb{R}^3: x^2+y^2<4,~0<z<4-x^2-y^2} $



I would also really like to know how I could plot this by using WolframAlpha?










share|cite|improve this question









$endgroup$












  • $begingroup$
    It seems off-topic to ask about 3D plotting using WolframAlpha, though I can imagine having access to it during exams would simplify a large number of tasks. In general there is no trick to visualizing 3D sets using pencil and paper, or rather the approaches (isometric drawing and orthographic projection) are reasonably well-known but not taught specifically in math courses.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:05














0












0








0





$begingroup$


durnig exams I often have the problem to visualize the sets I should work with, especially in 3D. So I wanted to ask if there is a trick on how to sketch the following set for example



$ G:={(x,y,z)^T in mathbb{R}^3: x^2+y^2<4,~0<z<4-x^2-y^2} $



I would also really like to know how I could plot this by using WolframAlpha?










share|cite|improve this question









$endgroup$




durnig exams I often have the problem to visualize the sets I should work with, especially in 3D. So I wanted to ask if there is a trick on how to sketch the following set for example



$ G:={(x,y,z)^T in mathbb{R}^3: x^2+y^2<4,~0<z<4-x^2-y^2} $



I would also really like to know how I could plot this by using WolframAlpha?







functional-analysis






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asked Dec 20 '18 at 18:58









JaneJane

31




31












  • $begingroup$
    It seems off-topic to ask about 3D plotting using WolframAlpha, though I can imagine having access to it during exams would simplify a large number of tasks. In general there is no trick to visualizing 3D sets using pencil and paper, or rather the approaches (isometric drawing and orthographic projection) are reasonably well-known but not taught specifically in math courses.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:05


















  • $begingroup$
    It seems off-topic to ask about 3D plotting using WolframAlpha, though I can imagine having access to it during exams would simplify a large number of tasks. In general there is no trick to visualizing 3D sets using pencil and paper, or rather the approaches (isometric drawing and orthographic projection) are reasonably well-known but not taught specifically in math courses.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:05
















$begingroup$
It seems off-topic to ask about 3D plotting using WolframAlpha, though I can imagine having access to it during exams would simplify a large number of tasks. In general there is no trick to visualizing 3D sets using pencil and paper, or rather the approaches (isometric drawing and orthographic projection) are reasonably well-known but not taught specifically in math courses.
$endgroup$
– hardmath
Dec 20 '18 at 19:05




$begingroup$
It seems off-topic to ask about 3D plotting using WolframAlpha, though I can imagine having access to it during exams would simplify a large number of tasks. In general there is no trick to visualizing 3D sets using pencil and paper, or rather the approaches (isometric drawing and orthographic projection) are reasonably well-known but not taught specifically in math courses.
$endgroup$
– hardmath
Dec 20 '18 at 19:05










1 Answer
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$begingroup$

HINT



Do you recognize the surface $z = x^{2} + y^{2}$? It is a paraboloid! The same applies to $z = -x^{2} - y^{2}$, which is the reflection of $z = x^{2} + y^{2}$ as to the plane $xy$. If you translate its vertice to $(0,0,4)$, you obtain the given surface when you restrict its domain to the circle $x^{2} + y^{2} < 4$.






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  • $begingroup$
    This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:07












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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









0












$begingroup$

HINT



Do you recognize the surface $z = x^{2} + y^{2}$? It is a paraboloid! The same applies to $z = -x^{2} - y^{2}$, which is the reflection of $z = x^{2} + y^{2}$ as to the plane $xy$. If you translate its vertice to $(0,0,4)$, you obtain the given surface when you restrict its domain to the circle $x^{2} + y^{2} < 4$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:07
















0












$begingroup$

HINT



Do you recognize the surface $z = x^{2} + y^{2}$? It is a paraboloid! The same applies to $z = -x^{2} - y^{2}$, which is the reflection of $z = x^{2} + y^{2}$ as to the plane $xy$. If you translate its vertice to $(0,0,4)$, you obtain the given surface when you restrict its domain to the circle $x^{2} + y^{2} < 4$.






share|cite|improve this answer









$endgroup$













  • $begingroup$
    This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:07














0












0








0





$begingroup$

HINT



Do you recognize the surface $z = x^{2} + y^{2}$? It is a paraboloid! The same applies to $z = -x^{2} - y^{2}$, which is the reflection of $z = x^{2} + y^{2}$ as to the plane $xy$. If you translate its vertice to $(0,0,4)$, you obtain the given surface when you restrict its domain to the circle $x^{2} + y^{2} < 4$.






share|cite|improve this answer









$endgroup$



HINT



Do you recognize the surface $z = x^{2} + y^{2}$? It is a paraboloid! The same applies to $z = -x^{2} - y^{2}$, which is the reflection of $z = x^{2} + y^{2}$ as to the plane $xy$. If you translate its vertice to $(0,0,4)$, you obtain the given surface when you restrict its domain to the circle $x^{2} + y^{2} < 4$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 20 '18 at 19:03









APC89APC89

2,371720




2,371720












  • $begingroup$
    This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:07


















  • $begingroup$
    This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
    $endgroup$
    – hardmath
    Dec 20 '18 at 19:07
















$begingroup$
This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
$endgroup$
– hardmath
Dec 20 '18 at 19:07




$begingroup$
This might help with visualization (and the general technique might be called finding cross-sections), but it avoids the issue of plotting. I'll let the OP be the judge whether it helps.
$endgroup$
– hardmath
Dec 20 '18 at 19:07


















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