Author 
Comment/Response 
Peter Marsh

11/29/03 01:56am
I'm sure you have already received an answer, but I have the same sort of problem. I can get Mathematica to graph ellipsoids, paraboloids, and hyperbolic paraboloids, but so far no luck with hyperboloids or elliptic cones (here x,y,and z are all second power.)
To graph an ellipsoid, you have to use the ParametricPlot3D function. Here is the input:
ParametricPlot3D[{5Cos[\[Phi]]Cos[\[Theta]], 3Sin[\[Phi]]Cos[\[Theta]],
2Sin[\[Theta]]}, {\[Phi], 0, 2\[Pi]}, {\[Theta], \[Pi]/2, \[Pi]/2}]
This uses a conversion of the original equation to spherical coordinates, but apparently the coordinate system in Mathematica is defined differently from that used in my calculus book. (Anton  6th edition)
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