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| Math Central | Quandaries & Queries |
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Question from ann, a parent: what does planar curve mean in your definition of a cone? |
Hi Ann,
A planar curve is one that lies in a plane. Some examples are
To be the base of a cone the planar curve must be closed. In the plane, a closed curve is a curve with no endpoints and which completely encloses an area. (See Wolfram Mathworld.) Thus the line and parabola above can not be the base of a cone.
An example of a curve that is not planar is the curve formed by a coil spring.
Penny
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