MathDB
TOT 070 1984 Autumn Train J4 rectangle inscribed in quadrilateral, ineq.

Source:

August 24, 2019
geometryrectangleperimetergeometric inequalitydiagonalinscribed

Problem Statement

Inside a rectangle is inscribed a quadrilateral, which has a vertex on each side of the rectangle. Prove that the perimeter of the inscribed quadrilateral is not smaller than double the length of a diagonal of the rectangle.
(V. V . Proizvolov , Moscow)