3.20 Crofton's method Here we wish to apply Crofton's method for finding mean values to the problem of finding the mean Euclidean distance,
where (X_{1}, Y_{1}) and (X_{2}, Y_{2}) are uniformly and independently distributed over a circle of radius r. Here, for instance, (X_{1}, Y_{1}) and (X_{2}, Y_{2}) could be the locations of an emergency and a helicopter response unit, respectively, and D would be the travel distance to the emergency.
