| 释义 |
torus (tori) Suppose that a circle of radius a is rotated through one revolution about a line, in the plane of the circle, a distance b from the centre of the circle, where b > a. The resulting surface or solid is called a torus, the shape of a ‘doughnut'. The surface area of this torus equals 4π2ab, and its volume equals 2π2a2b. More generally, the term ‘torus' applies to an orientable closed surface with g holes, called the genus of the torus. See classification theorem for surfaces.
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