medium   Probability

Uniform Angle Overlap

A release-checked medium problem for training Law of Total Probability, Uniform, Expected Value, Continuous Random Variables.

Question

Suppose that we have a unit circle sitting on the $(x,y)$ plane centered at $(0,0)$. We randomly generate an angle $\theta \sim \unif{0}{2\pi}$, and move along the perimeter of the circle $\theta$ radians counterclockwise from the point $(1,0)$, coloring the perimeter orange as we go. We then generate two more angles, $\alpha$ and $\beta$, independently from $\unif{0}{2\pi}$. An arc along the perimeter of the circle of length $\beta$ radians starting from the point that is $\alpha$ radians counterclockwise from $(1,0)$ is then colored green. What is the probability that the orange and green regions are disjoint?

Practice focus

This Probability problem is tagged Law of Total Probability, Uniform, Expected Value, Continuous Random Variables. State the random variables and conditioning information explicitly, then check the result against boundary cases before opening hints or a solution.

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