Perseus
fl. second century B.C.
Greek mathematician known chiefly through Proclus's (410?-485) comments on his development of spiric surfaces and sections. A spiric surface, as defined by Proclus, is one in which a circle revolves around a straight line (the axis of revolution) but always remains in the same plane as the axis.
Depending on whether the axis cuts the circle, is tangent to it, or is outside the circle, three distinct varieties of spiric surface are possible. (Visually these resemble an oval, a figure 8 with a broad waist, and a figure 8 with a narrow waist.) Proclus compared Perseus's work on spiric sections—formed when a plane parallel to the axis of revolution cuts the spiric surface—to Apollonius's (c. 262-c. 190 B.C.) studies of conics.
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