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Probability 6.0/10

Cutting Off a Segment

Two points are chosen independently and uniformly on the boundary of a disk, and the chord joining them cuts the disk into two pieces. What is the expected area of the smaller piece, as a fraction of the disk's area? Give an exact closed form, or a decimal rounded to 4 places.

Related problems & prerequisites

Worth solving first

Source: Classic geometric-probability exercise in wide circulation; no traceable original source. Statement written for AxiomIQ.