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Source: Switzerland Final Round 2021 P8

February 24, 2021
geometry

Problem Statement

Let △ABC\triangle ABC be a triangle with AB=ACAB =AC and ∠BAC=20∘\angle BAC = 20^{\circ}. Let DD be point on the side ABAB such that ∠BCD=70∘\angle BCD = 70^{\circ}. Let EE be point on the side ACAC such that ∠CBE=60∘\angle CBE = 60^{\circ}. Determine the value of angle ∠CDE\angle CDE.
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