A gallery of conics by five elements (Q2929580)

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scientific article; zbMATH DE number 6369206
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English
A gallery of conics by five elements
scientific article; zbMATH DE number 6369206

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    13 November 2014
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    geometry of conics
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    involutory projectivity
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    common harmonics of two pairs of collinear points
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    pencil of conics
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    range of conics
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    quadratic transformation
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    eleven point conic
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    eleven tangent conic
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    Desargues' theorem for pencils of conics
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    Desargues' theorem for ranges of conics
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    Plücker's theorem
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    Pascal's theorem
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    Brianchon's theorem
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    A gallery of conics by five elements (English)
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    This paper addresses the beginner in constructive geometry of conics in the projectively extended real affine plane; the author offers an extensive training in dealing with infinite elements and with duality. The main task says: A conic \(c\) is given by five points in general position; construct a further point of the conic (is done via Pascal's theorem). The author discusses all further eleven (not necessarily unique) determinations of a conic by points and tangents using well-known theorems which are listed above as keywords.NEWLINENEWLINEOccasionally the author leaves the frame of plane geometry and employs descriptive geometry when a task is solved by spacial interpretation.NEWLINENEWLINEThe reviewer considers the gallery to be incomplete because the determinations of conics by elements of osculation or hyperosculation are missing.
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