单词 | focal conic |
释义 | > as lemmasfocal conic focal conic n. Geometry (now rare) any of the several conics formed in each of the principal planes of a quadric surface by its foci. ΚΠ 1842 London, Edinb., & Dublin Philos. Mag. 21 64 Let the points on the focal conic, at which the tangent is parallel to the trace of the tangent plane, be considered analogous to foci. 1874 Messenger Math. 3 132 Suppose we describe all the quadrics which have given focal conics. Begin with the ellipsoid of infinite size, and let its axes diminish. 1960 W. H. McCrea Anal. Geom. Three Dimensions (rev. ed.) 134 Every point of the conic..lying in the plane ζ = 0 is a focus; this is called a focal conic. < as lemmas |
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