Problem of the Week 1030

A Tilted Average

A tennis ball of diameter 1 has a disk inside it, sewn in along the equator. It is tossed around and lands in a random orientation. The disk projects down to an ellipse, with major axis of length 1. What is the expected length of the minor axis?

© Copyright 2005 Stan Wagon. Reproduced with permission.

18 March 2005