geom
31conic section — Geom. a curve formed by the intersection of a plane with a right circular cone; an ellipse, a circle, a parabola, or a hyperbola. Also called conic. [1655 65] * * * Any two dimensional curve traced by the intersection of a right circular cone… …
32conjugate axis — Geom. 1. the axis of a hyperbola perpendicular to the transverse axis at a point equidistant from the foci. 2. the segment of this axis equal to one side of a rectangle that has its other side equal to the transverse axis and diagonals that are… …
33corresponding angles — Geom. two nonadjacent angles made by the crossing of two lines by a third line, one angle being interior, the other exterior, and both being on the same side of the third line. Cf. alternate angles. [1790 1800] * * * …
34Desargues's theorem — Geom. the theorem that if two triangles are so related that the lines joining corresponding vertices meet in a point, then the extended corresponding lines of the two triangles meet in three points, all on the same line. [named after G.… …
35dihedral angle — Geom. 1. the angle between two planes in a dihedron. 2. dihedron. [1820 30] * * * …
36duplication of the cube — Geom. the insoluble problem of constructing a cube having twice the volume of a given cube, using only a ruler and compass. [1650 60] * * * …
37elliptic paraboloid — Geom. a paraboloid that can be put into a position such that its sections parallel to one coordinate plane are ellipses, while its sections parallel to the other two coordinate planes are parabolas. Cf. hyperbolic paraboloid. * * * …
38exterior angle — Geom. 1. an angle formed outside parallel lines by a third line that intersects them. See diag. under interior angle. 2. an angle formed outside a polygon by one side and an extension of an adjacent side; the supplement of an interior angle of… …
39face angle — Geom. the angle formed by two successive edges of a polyhedron. [1910 15] * * * …
40hyperbolic geometry — Geom. the branch of non Euclidean geometry that replaces the parallel postulate of Euclidean geometry with the postulate that two distinct lines may be drawn parallel to a given line through a point not on the given line. Cf. Riemannian geometry …
