MathDB
Inequality related to defining convex body from halfspaces

Source: Miklós Schweitzer 2019, Problem 5

December 27, 2019
inequalities

Problem Statement

Let SRdS \subset \mathbb{R}^d be a convex compact body with nonempty interior. Show that there is an α>0\alpha > 0 such that if S=iIHiS = \cap_{i \in I} H_i, where II is an index set and (Hi)iI(H_i)_{i \in I} are halfspaces, then for any PRdP \in \mathbb{R}^d, there is an iIi \in I for which dist(P,Hi)αdist(P,S)\mathrm{dist}(P, H_i) \ge \alpha \, \mathrm{dist}(P, S).