MathDB
JBMO 2018 P4

Source: JBMO

June 21, 2018
geometrycircumcircle

Problem Statement

Let △ABC\triangle ABC and A′A',B′B',C′C' the symmetrics of vertex over opposite sides.The intersection of the circumcircles of △ABB′\triangle ABB' and △ACC′\triangle ACC' is A1A_1.B1B_1 and C1C_1 are defined similarly.Prove that lines AA1AA_1,BB1BB_1 and CC1CC_1 are concurent.
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