Porism
Porism Po"rism, n. [Gr. ? a thing procured, a deduction from a demonstration, fr. ? to bring, provide: cf. F. porisme.] 1. (Geom.) A proposition affirming the possibility of finding such conditions as will render a certain determinate problem indeterminate or capable of innumerable solutions. --Playfair. [1913 Webster]

2. (Gr. Geom.) A corollary. --Brande & C. [1913 Webster]

Note: Three books of porisms of Euclid have been lost, but several attempts to determine the nature of these propositions and to restore them have been made by modern geometers. [1913 Webster]


The Collaborative International Dictionary of English. 2000.

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  • porism — /pöˈ or pōˈri zm/ noun 1. In ancient Greek geometry, a corollary 2. Also a kind of proposition intermediate between a problem and a theorem, according to some a proposition affirming the possibility of finding such conditions as will render a… …   Useful english dictionary

  • porism — [pō′riz΄əm, pôr′iz΄əm] n. 〚ME porysme < ML porisma < Gr, lit., a thing brought < porizein, to bring < poros, passage: see PORE2〛 Ancient Math. a geometrical proposition variously defined, as a) a proposition deduced from some other demonstrated… …   Universalium

  • porism — [pō′riz΄əm, pôr′iz΄əm] n. [ME porysme < ML porisma < Gr, lit., a thing brought < porizein, to bring < poros, passage: see PORE2] Ancient Math. a geometrical proposition variously defined, as a) a proposition deduced from some other… …   English World dictionary

  • Porism — The subject of porisms is perplexed by the multitude of different views which have been held by geometers as to what a porism really was and is.The treatise which has given rise to the controversies on this subject is the Porisms of Euclid, the… …   Wikipedia

  • porism —   n. geometric proposition that it is possible, in certain conditions, for a problem to have any number of solutions …   Dictionary of difficult words

  • Poncelet's porism — In geometry, Poncelet s porism, named after French engineer and mathematician Jean Victor Poncelet, states the following: Let C and D be two plane conics. If it is possible to find, for a given n > 2, one n sided polygon which is simultaneously… …   Wikipedia

  • Steiner chain — In geometry, a Steiner chain is a set of n circles, all of which are tangent to two given non intersecting circles (blue and red in Figure 1), where n is finite and each circle in the chain is tangent to the previous and next circles in the chain …   Wikipedia

  • Poristic — Po*ris tic, Poristical Po*ris tic*al, a. [Gr. ? for providing, ? provided.] Of or pertaining to a porism; of the nature of a porism. [1913 Webster] …   The Collaborative International Dictionary of English

  • Poristical — Poristic Po*ris tic, Poristical Po*ris tic*al, a. [Gr. ? for providing, ? provided.] Of or pertaining to a porism; of the nature of a porism. [1913 Webster] …   The Collaborative International Dictionary of English

  • Ptolemy's theorem — In mathematics, Ptolemy s theorem is a relation in Euclidean geometry between the four sides and two diagonals or chords of a cyclic quadrilateral. The theorem is named after the Greek astronomer and mathematician Ptolemy (Claudius Ptolemaeus).If …   Wikipedia

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