Conic Sections - The Ellipse
On an (x, y) graph an ellipse can have this shape:
If a plane intersects the cone all of the way around but is not perpendicular to the axis, the conic section is an ellipse. This is shown below:
Here is a VRML animation that shows several possibilities for forming an ellipse by intersecting a cone and a plane. (For help with VRML go here.)
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