MathDB
AB = DE ,Nice

Source: Baltic Way 1999

September 1, 2008
trigonometrygeometrygeometric transformationrotationgeometry proposed

Problem Statement

Let ABCABC be a triangle with ∠C=60∘\angle C=60^\circ and AC<BCAC<BC. The point DD lies on the side BCBC and satisfies BD=ACBD=AC. The side ACAC is extended to the point EE where AC=CEAC=CE. Prove that AB=DEAB=DE.
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