Assume three points, one of which is red, are uniformly and independently distributed over the circumference of a circular track, which has a total length of 1. Equivalently, you can interpret the circle as
a unit interval with its two ends tied together, and all distances of points are measured in terms of the
length on the track. The Figure below gives a simple illustration.
X
1. Let X be the distance of the red point to its neighbor in the counter-clockwise direction. Find the
PDF of X.
2. Let Y be the minimum distance of the red point to its nearest neighbor (either in the clockwise or
counter-clockwise direction, whichever is smaller). Find the PDF of Y.
3. Let Z be the minimum distance between any two of the points. Find the PDF of Z.
Hint: You can represent the event {Z > z} in terms of two random variables that are uniformly
distributed on a unit square. To nd P(Z > z), determine the area that corresponds to {Z > z}
graphically