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angle wanted, cyclic ABCD, AB=BC=CD, AE//CD (2020 Kyiv City MO 9.4.1)

Source:

September 20, 2020
geometryanglesequal segments

Problem Statement

The points A,B,C,DA, B, C, D are selected on the circle as followed so that AB=BC=CDAB = BC = CD. Bisectors of ∠ABD\angle ABD and ∠ACD\angle ACD intersect at point EE. Find ∠ABC\angle ABC, if it is known that AE∥CDAE \parallel CD.
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