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isosceles triangle wanted, parallelogram related

Source: TOT 528 1997 Spring J O5 - Tournament Of Towns

September 11, 2024
geometryparallelogram

Problem Statement

EE is the midpoint of the side ADAD of a parallelogram ABCDABCD. FF is the foot of the perpendicular from the vertex BB to the line CECE. Prove that ABFABF is an isosceles triangle.
(MA Bolchkevich)
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