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20

Part of 2018 Iran MO (1st Round)

Problems(1)

Angles in cyclic quadrilateral - Iran First Round 2018, P20

Source:

3/7/2021
In the convex and cyclic quadrilateral ABCDABCD, we have ∠B=110∘\angle B = 110^{\circ}. The intersection of ADAD and BCBC is EE and the intersection of ABAB and CDCD is FF. If the perpendicular from EE to ABAB intersects the perpendicular from FF to BCBC on the circumcircle of the quadrilateral at point PP, what is ∠PDF\angle PDF in degrees?
geometrycyclic quadrilateral