geom
51parallel axiom — Geom. See parallel postulate. * * * …
52parallel postulate — Geom. the axiom in Euclidean geometry that only one line can be drawn through a given point so that the line is parallel to a given line that does not contain the point. Also called parallel axiom. * * * One of the five postulates, or axioms, of… …
53parallel projection — Geom. a projection from one plane to a second plane in which the lines joining points on the first plane and corresponding images are parallel. * * * …
54Pascal's limaçon — Geom. limaçon. [1950 55; after Blaise PASCAL, who studied and named it] * * * …
55Pascal's theorem — Geom. the theorem that the lines joining adjacent vertices of a hexagon intersect the same straight line if alternate vertices lie on two intersecting straight lines. [named after PASCAL] * * * …
56Platonic solid — Geom. one of the five regular polyhedrons: tetrahedron, octahedron, hexahedron, icosahedron, or dodecahedron. [1950 55] * * * also known as regular polyhedron Geometric solid all of whose faces are identical regular polygons and all of whose… …
57polyhedral angle — Geom. a configuration consisting of the lateral faces of a polyhedron around one of its vertices. The portion of a pyramid including one of its points is such a configuration. See illus. under pyramid. [1860 65] * * * …
58Pythagorean theorem — Geom. the theorem that the square of the hypotenuse of a right triangle is equal to the sum of the squares of the other two sides. [1905 10] * * * Rule relating the lengths of the sides of a right triangle. It says that the sum of the squares of… …
59radical axis — Geom. the line such that tangents drawn from any point of the line to two given circles are equal in length. [1840 50] * * * …
60rectangular hyperbola — Geom. a hyperbola with transverse and conjugate axes equal to each other. Also called equiangular hyperbola, equilateral hyperbola. [1880 85] * * * …
