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# 微積分 Identify the surface

Identify the surface whose equation is as following:

z=4-r^2

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- 天助Lv 71 decade agoFavorite Answer
z=4-r^2 is a elliptic-paraboloid surface in the cyclindrical coordinate system.

This surface is the same as z=4-x^2-y^2 in the Cartesian coordinate system,

and can be obtained by rotating the plane curve z=4-y^2 about the z-axis,

or by rotating the plane curve z=4-x^2 about the z-axis.

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