<Tri-2023-2072>, hint
Let I. I'be the incenter of triangles ABC. ADE, which are similar. and T be the intesection of DE and AK ( A,I,K are collinear)
Apply Menelaus theorem
Hence m to triangle ALT with traverse PI'Q.
(AQ/QL)x(LP/PT)x(TI'/I'A)=1.
Since TI'/I'A=KI/IA ( Triangles ADE and ABC are simialr). Let A' be antipode of A
LP/PT=AA'/(AA'-AI). AA'=2R sin(B+A/2), AI=(b+c-a/2)/cosA/2
AA'=2R cos(B-C/2), AI=2R (cos(B-C)/2-cos<B+C)2. AA'/(AA'-AI)=cos(B+C/2)/cos(B-C)/2
LP/PT=(b+c)/a=(cos(B-C)/2)/(cos(B+C)/2). Hence Q I' P are collinear.
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