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MathNet 2015-part-04 — 191 problems (EN–VI) Question 42

Math Olympiad Vault · MathNet 2015-part-04 — 191 problems (EN–VI)

Question 42

In a triangle $ABC$, $D$ is the intersection of the internal bisector of $\angle BAC$ with side $BC$. Let $P$ be the second intersection of the external bisector of $\angle BAC$ with the circumcircle of $\triangle ABC$. A circle through $A$ and $P$ intersects segment $BP$ in its interior in $E$ and segment $CP$ in its interior in $F$. Prove that $\angle DEP = \angle DFP$.