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An accurate 12-hour analog clock has an hour hand

Source: IMO Longlist 1989, Problem 101

September 18, 2008
algebra unsolvedalgebra

Problem Statement

An accurate 12-hour analog clock has an hour hand, a minute hand, and a second hand that are aligned at 12:00 o’clock and make one revolution in 12 hours, 1 hour, and 1 minute, respectively. It is well known, and not difficult to prove, that there is no time when the three hands are equally spaced around the clock, with each separating angle 2π3. \frac{2 \cdot \pi}{3}. Let f(t),g(t),h(t) f(t), g(t), h(t) be the respective absolute deviations of the separating angles from \frac{2 \cdot \pi}{3} at t t hours after 12:00 o’clock. What is the minimum value of max{f(t),g(t),h(t)}? max\{f(t), g(t), h(t)\}?