Quote:
Originally Posted by bob jenkins
The "right" means that the "ends" of the finite section are perpendicular (at a "right angle") to the "sides". In theory, a cylinder is analogous to a line, it has no end points. As the rest of the quote shows, in practice, it's used as being analogous to a line segment.
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Thanks. I got it mixed up. This is what threw me: "A cylinder is taken to mean a finite section of a right circular cylinder with its ends closed to form two circular surfaces", from Wikepedia. How can one look at a finite section of something that is already finite? The definition implies that the right cylinder is infinite. Either I misunderstood the definition, or the definition is poorly written. I didn't follow my own rule here: It's alright to use Wikepedia for your first source, but don't use it as your only source.
In summary: A cylinder has no "top", or "bottom" (the circular planes), so the "sides" go on infinitely, the center being a line. A right cylinder has a "top", and a "bottom", perpendicular to the "sides", is therefore finite, the center being a line segment, and volume, and surface area, can be defined, and measured.
Our basketball cylinder, as described in basketball interference, has a bottom, the ring, but has no top, theoretically, the center being a ray, so it's not a true cylinder. Is is a right cylinder, with only a "bottom", and no "top"?