Excerpt from How to Move a Chair Through a Door To move a given chair through a door, a natural question is how wide the door should be. The minimum width of a passable door is called the width of the chair. The question was first raised by Gilbert Strang [str82] who studied the case of convex chairs in two and three dimensions.' We focus on the polygonal chairs in this paper but allow non-convex chairs. Although the notion of width for convex chairs is easily captured, the width of non-convex chairs admits several reasonable interpretations. We will note three possibilities in this paper. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.