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4.

Part of 2017 Polish Junior Math Olympiad First Round

Problems(1)

2017 Polish Junior Math Olympiad First Round P4

Source: 2017 Polish Junior Math Olympiad First Round

5/23/2023
Quadrilateral ABCDABCD is inscribed in a circle with ∠ABC=60∘\angle ABC=60^\circ and BC=CDBC=CD. Prove that AB=AD+DCAB=AD+DC.
geometry