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  2. Ptolemy's inequality - Wikipedia

    en.wikipedia.org/wiki/Ptolemy's_inequality

    For four points in order around a circle, Ptolemy's inequality becomes an equality, known as Ptolemy's theorem: ¯ ¯ + ¯ ¯ = ¯ ¯. In the inversion-based proof of Ptolemy's inequality, transforming four co-circular points by an inversion centered at one of them causes the other three to become collinear, so the triangle equality for these three points (from which Ptolemy's inequality may ...

  3. Ptolemaic graph - Wikipedia

    en.wikipedia.org/wiki/Ptolemaic_graph

    In graph theory, a Ptolemaic graph is an undirected graph whose shortest path distances obey Ptolemy's inequality, which in turn was named after the Greek astronomer and mathematician Ptolemy. The Ptolemaic graphs are exactly the graphs that are both chordal and distance-hereditary ; they include the block graphs [ 1 ] and are a subclass of the ...

  4. Category:Geometric inequalities - Wikipedia

    en.wikipedia.org/.../Category:Geometric_inequalities

    Print/export Download as PDF; Printable version; In other projects ... Ptolemy's inequality; Pu's inequality; R. Riemannian Penrose inequality; Ring lemma; S.

  5. Casey's theorem - Wikipedia

    en.wikipedia.org/wiki/Casey's_theorem

    In mathematics, Casey's theorem, also known as the generalized Ptolemy's theorem, is a theorem in Euclidean geometry named after the Irish mathematician John Casey. Formulation of the theorem [ edit ]

  6. Ptolemy's theorem - Wikipedia

    en.wikipedia.org/wiki/Ptolemy's_theorem

    More generally, if the quadrilateral is a rectangle with sides a and b and diagonal d then Ptolemy's theorem reduces to the Pythagorean theorem. In this case the center of the circle coincides with the point of intersection of the diagonals. The product of the diagonals is then d 2, the right hand side of Ptolemy's relation is the sum a 2 + b 2.

  7. File:Ptolemy Inequality.svg - Wikipedia

    en.wikipedia.org/wiki/File:Ptolemy_Inequality.svg

    The following other wikis use this file: Usage on ar.wikipedia.org متفاوتة بطليموس; Usage on ca.wikipedia.org Teorema de Ptolemeu

  8. Angelina Jolie Gets Asked 'the Most Insane Question.' Here's ...

    www.aol.com/angelina-jolie-gets-asked-most...

    Angelina Jolie balked at a question regarding whether there should be a biopic about her life.. When Jolie, 49, and her Maria director Pablo Larraín spoke with the U.K.'s The Times to promote ...

  9. Planisphaerium - Wikipedia

    en.wikipedia.org/wiki/Planisphaerium

    The Planisphaerium is a work by Ptolemy. The title can be translated as "celestial plane" or "star chart". In this work Ptolemy explored the mathematics of mapping figures inscribed in the celestial sphere onto a plane by what is now known as stereographic projection. This method of projection preserves the properties of circles.