MathDB
IMC 1996 Problem 10

Source: IMC 1996

March 4, 2021
conicsellipsegeometry

Problem Statement

Let BB be a bounded closed convex symmetric (with respect to the origin) set in R2\mathbb{R}^{2} with boundary Γ\Gamma. Let BB have the property that the ellipse of maximal area contained in BB is the disc DD of radius 11 centered at the origin with boundary CC. Prove that AΓA \cap \Gamma \ne \emptyset for any arc AA of CC of length l(A)π2l(A)\geq \frac{\pi}{2}.