Point-to-line distances in the plane of a triangle (Q1344004)

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scientific article; zbMATH DE number 720430
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Point-to-line distances in the plane of a triangle
scientific article; zbMATH DE number 720430

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    Point-to-line distances in the plane of a triangle (English)
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    27 August 1995
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    In the (Euclidean) plane of a triangle \(\Delta\) ninety-one specific notable points (called ``centers'') are considered (among them: centroid, circumcenter, incenter, orthocenter, symmedian point, Feuerbach point, Fermat point of \(\Delta)\), along with the Euler line \(e\) and the ortho- Euler line \(\overline e\) (line perpendicular to \(e\) that passes through the orthocenter of \(\Delta)\). Having chosen a fixed point \(P_ 0\) not lying on \(e\), for any point \(P\) in the plane of \(\Delta\) let be \(D(P):\) = (directed distance between \(P\) and \(e)\)/(directed distance between \(P_ 0\) and \(e)\); define \(\overline D(P)\) analogously, by replacing \(e\) by \(\overline e\). Now the author first considers the two problems: (1) For what centers \(X\) and \(Y\) is \(D(X) \leq D(Y)\) for all triangles \(\Delta\)? (2) Evaluate \(\inf D(X)\) and \(\sup D(X)\) (for a certain center \(X\) of \(\Delta)\) over all triangles \(\Delta\)! Then, by replacing \(e\) by \(\overline e\), one gets two analogous problems (3), (4). Starting from these four problems, numerous inequalities (most of which are new) involving the 91 specific centers and the lines \(e\), \(\overline e\) of a triangle \(\Delta\) are presented; however, they are only conjectured, not proved: each inequality was detected by computer and then confirmed for 10,740 triangles.
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    notable point
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    center
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    notable line
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    triangle
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    Euler line
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    ortho-Euler line
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    distance
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