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Three geometries – Euclidean, Hyperbolic, Elliptical

Three geometries - Euclidean, Hyperbolic, Elliptical
Three geometries – Euclidean, Hyperbolic, Elliptical

There are precisely three different classes of three-dimensional constant-curvature geometry: Euclidean, hyperbolic and elliptic geometry. The three geometries are all built on the same first four axioms, but each has a unique version of the fifth axiom, also known as the parallel postulate. The 1868 Essay on an Interpretation of Non-Euclidean Geometry by Eugenio Beltrami (1835 – 1900) proved the logical consistency of the two Non-Euclidean geometries, hyperbolic and elliptical.

The parallel postulate is as follows for the corresponding geometries.

Euclidean geometry: Playfair’s version: “Given a line l and a point P not on l, there exists a unique line m through P that is parallel to l.” Euclid’s version: “Suppose that a line l meets two other lines m and nso that the sum of the interior angles on one side of lis less than 180°. Then m and n intersect in a point on that side of l.” These two versions are equivalent; though Playfair’s may be easier to conceive, Euclid’s is often useful for proofs.

Hyperbolic geometry: Given an arbitrary infinite line l and any point P not on l, there exist two or more distinct lines which pass through P and are parallel to l.

Elliptic geometry: Given an arbitrary infinite line land any point P not on l, there does not exist a line which passes through P and is parallel to l.

Source and more info: https://en.m.wikibooks.org/wiki/Geometry/Hyperbolic_and_Elliptic_Geometry

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Unity of Geometry

geometry

Unity of Geometry – Root Power : by Jonathan Quintin

Unity of Geometry Root-Power – the Triangle – excerpt

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      Plato – The Timaeus

      Plato - The Timaeus

      The Timaeus

      The Composition of the Soul

      “We shall therefore borrow all our Rules for the Finishing our Proportions, from the Musicians, who are the greatest Masters of this Sort of Numbers, and from those Things wherein Nature shows herself most excellent and compleat.” Leon Battista Alberti (1407-1472).

      arithmetic, geometric, harmonic means

      arithmetic, geometric, harmonic means

      Continue reading Plato – The Timaeus