Conic Sections - The Line
On an (x, y) graph a line can have this shape:
If a plane intersects the cone when it is slanted the same as the side of the cone, (formally, when it is parallel to the slant height), and when it passes through the tip of the cone, (formally when it passes through the vertex), the conic section is a line. This is shown below:
Here is a VRML world that shows how to form a line by intersecting a cone and a plane. (For help with VRML go here.)
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