MathDB
perpendicular planes

Source: Ukraine 1997 grade 10

July 21, 2009
geometry proposedgeometry

Problem Statement

Two regular pentagons ABCDE ABCDE and AEKPL AEKPL are placed in space so that \angle DAK\equal{}60^{\circ}. Prove that the planes ACK ACK and BAL BAL are perpendicular.
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