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MathNet 2025 — 50 problems with figures (EN–VI) Question 49

Math Olympiad Vault · MathNet 2025 — 50 problems with figures (EN–VI)

Question 49

In the triangle $ABC$, $\angle B \gt 90^\circ$, the incircle touches the sides $BC$ and $CA$ at $D$ and $E$, respectively. The lines $ED$ and $AB$ intersect at $P$. The incircle of the triangle $AEP$ touches the sides $PE$ and $AP$ at $D_1$ and $E_1$, respectively. The lines $E_1D_1$ and $AE$ intersect at $P_1$. Suppose $P, C, E, B$ are concyclic. Prove that $BE$ is parallel to $PP_1$.