MathDB
Angle bisectors meets the circumcircle

Source: 2016 Azerbaijan JBMO TST, D2 P2

July 29, 2023
geometryangle bisectorcircumcircle

Problem Statement

Let the angle bisectors of BAC,\angle BAC, CBA,\angle CBA, and ACB\angle ACB meets the circumcircle of ABC\triangle ABC at the points M,N,M,N, and K,K, respectively. Let the segments ABAB and MKMK intersects at the point PP and the segments ACAC and MNMN intersects at the point Q.Q. Prove that PQBCPQ\parallel BC