3.21 Expected values Suppose that two points (X₁, Y₁) and (X₂, Y₂) are uniformly and independently distributed over a circle of area A. Assume that the travel distance D between the two points is the right-angle travel distance

D = | X₁ - X₂| + |Y₁ - Y₂|

Argue that

Hint: Consider D to be the product of the Euclidean distance and a scaling factor R, the ratio between the right-angle and Euclidean distances.