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IMO LongList 1967, Poland 6

Source: IMO LongList 1967, Poland 6

December 16, 2004
geometrycircumcirclereflectionTriangleconcurrencyIMO ShortlistIMO Longlist

Problem Statement

A line ll is drawn through the intersection point HH of altitudes of acute-angle triangles. Prove that symmetric images la,lb,lcl_a, l_b, l_c of ll with respect to the sides BC,CA,ABBC,CA,AB have one point in common, which lies on the circumcircle of ABC.ABC.
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