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# samuel peters

In the latter case one obtains hyperbolic geometry and elliptic geometry, the traditional non-Euclidean geometries. [21] There are Euclidean, elliptic, and hyperbolic geometries, as in the two-dimensional case; mixed geometries that are partially Euclidean and partially hyperbolic or spherical; twisted versions of the mixed geometries; and one unusual geometry that is completely anisotropic (i.e. Elliptic geometry is an example of a geometry in which Euclid's parallel postulate does not hold. Khayyam, for example, tried to derive it from an equivalent postulate he formulated from "the principles of the Philosopher" (Aristotle): "Two convergent straight lines intersect and it is impossible for two convergent straight lines to diverge in the direction in which they converge. The proofs put forward in the fourteenth century by the Jewish scholar Levi ben Gerson, who lived in southern France, and by the above-mentioned Alfonso from Spain directly border on Ibn al-Haytham's demonstration. A triangle is defined by three vertices and three arcs along great circles through each pair of vertices. There’s hyperbolic geometry, in which there are infinitely many lines (or as mathematicians sometimes put it, “at least two”) through P that are parallel to ℓ. In his reply to Gerling, Gauss praised Schweikart and mentioned his own, earlier research into non-Euclidean geometry. If the sum of the interior angles α and β is less than 180°, the two straight lines, produced indefinitely, meet on that side. For example, the sum of the angles of any triangle is always greater than 180°. Elliptic geometry is a non-Euclidean geometry, in which, given a line L and a point p outside L, there exists no line parallel to L passing through p.Elliptic geometry, like hyperbolic geometry, violates Euclid's parallel postulate, which can be interpreted as asserting that there is exactly one line parallel to L passing through p.In elliptic geometry, there are no parallel lines at all. In order to achieve a [31], Another view of special relativity as a non-Euclidean geometry was advanced by E. B. Wilson and Gilbert Lewis in Proceedings of the American Academy of Arts and Sciences in 1912. In geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. When it is recalled that in Euclidean and hyperbolic geometry the existence of parallel lines is established with the aid of the assumption that a straight line is infinite, it comes as no surprise that there are no parallel lines in the two new, elliptic geometries. There’s hyperbolic geometry, in which there are infinitely many lines (or as mathematicians sometimes put it, “at least two”) through P that are parallel to ℓ. 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