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pyramid, in geometry

(Encyclopedia)CE5 Pyramid pyramid, in geometry, solid figure bounded by a polygon (the base, or directrix) and the surface generated by a moving line (the generator) passing through a fixed point (vertex) and c...

non-Euclidean geometry

(Encyclopedia)non-Euclidean geometry, branch of geometry in which the fifth postulate of Euclidean geometry, which allows one and only one line parallel to a given line through a given external point, is replaced b...

quadrant, in analytic geometry

(Encyclopedia)quadrant. 1 In analytic geometry, one of the four regions of the plane determined by two lines, the x-axis and the y-axis. Commonly these lines are drawn perpendicular to each other, and the quadrants...

Steiner, Jakob

(Encyclopedia)Steiner, Jakob yäˈkôp shtīˈnər [key], 1796–1863, Swiss mathematician. He was largely self-taught and was professor of geometry at the Univ. of Berlin from 1834. A pioneer in the development of...

Erlangen program

(Encyclopedia)Erlangen program: see geometry.

Monge, Gaspard, comte de Péluse

(Encyclopedia)Monge, Gaspard, comte de Péluse gäspärˈ môNzh kôNt də pālüzˈ [key], 1746–1818, French mathematician, physicist, and public official. He was distinguished for his geometrical research, whic...

Chern, Shiing-Shen

(Encyclopedia)Chern, Shiing-Shen, 1911–2004, Chinese-American mathematician, b. Kashing (now Jiaxing), China, D.Sc. Hamburg, 1936. While undertaking graduate studies in China (1932–34), Chern developed what bec...

Darboux, Jean Gaston

(Encyclopedia)Darboux, Jean Gaston zhäN gästôNˈ därbo͞oˈ [key], 1842–1917, French mathematician. He is known for his work on orthogonal surfaces and for his application of infinitesimal calculus to geometr...

Lobachevsky, Nikolai Ivanovich

(Encyclopedia)Lobachevsky, Nikolai Ivanovich nyĭkəlīˈ ēväˈnəvĭch ləbəchĕfˈskē [key], 1793–1856, Russian mathematician. A pioneer in non-Euclidean geometry, he challenged Euclid's fifth postulate tha...

triangle , in mathematics

(Encyclopedia)triangle, in mathematics, plane figure bounded by three straight lines, the sides, which intersect at three points called the vertices. Any one of the sides may be considered the base of the triangle....