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<CDE=<BEF wanted, 2 parallelograms, AC=AD, AE=2CD

Source: Champions Tournament (Ukraine) - Турнір чемпіонів - 2018 Seniors p3

September 2, 2020
geometryparallelogramequal anglesequal segmentsChampions Tournament

Problem Statement

The vertex FF of the parallelogram ACEFACEF lies on the side BCBC of parallelogram ABCDABCD. It is known that AC=ADAC = AD and AE=2CDAE = 2CD. Prove that ∠CDE=∠BEF\angle CDE = \angle BEF.
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