Definition of Terms, ContinuedSolids(Continued)Cylinders are two parallel bases formed by a fixed curve or directrixrevolving around a straight line or generatrix at the center. The generatrix atthe center of the cylinder is also called an axis. The height of the cylinder iscalled the altitude. Any point along the edges of the cylinder is referred to asan element. Right circular cylinders have lateral edges perpendicular to thebases and oblique circular cylinders have lateral edges oblique to the bases.Moving a point around and along the surface of a cylinder with uniformangular velocity to the axis and with a uniform linear velocity in the directionof the axis produces a helix.You may construct a helix using a cylinder orcone.Figure 2-12 show examples of cylinders and a helix.Figure 2-12.—Cylinders and a helix.Continued on next page2-14

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