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July 3, 2008
geometryparallelogramvectortrigonometrygeometric transformationreflectioncyclic quadrilateral

Problem Statement

The diagonals of the cyclic quadrilateral ABCD ABCD are intersecting at the point E E. K K and M M are the midpoints of AB AB and CD CD, respectively. Let the points L L on BC BC and N N on AD AD s.t. EL⊥BC EL\perp BC and EN⊥AD EN\perp AD.Prove that KM⊥LN KM\perp LN.
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