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Cylinder | ![]() |
In mathematics, a cylinder is a quadric surface, with the following equation in Cartesian coordinates:
This equation is for an elliptic cylinder, a generalization of the ordinary, circular cylinder (a = b). Even more general is the generalized cylinder: the cross-section can be any curve.
The cylinder is a degenerate quadric because at least one of the coordinates (in this case z) does not appear in the equation. By some definitions the cylinder is not considered to be a quadric at all.
In common usage, a cylinder is taken to mean a finite section of a right circular cylinder with its ends closed to form two circular surfaces, as in the figure (right). If the cylinder has a radius r and length (height) h, then its volume is given by
and its surface area is
(source: Cylinder (geometry). (2006, December 13). In Wikipedia, The Free Encyclopedia. Retrieved 14:01, December 21, 2006, from http://en.wikipedia.org/w/index.php?title=Cylinder_%28geometry%29&oldid=94010720)
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