MathDB
UFO can catch the turtle for any inital position

Source: IMO LongList 1970 - P55

May 24, 2011
trigonometrycombinatorics unsolvedcombinatorics

Problem Statement

A turtle runs away from an UFO with a speed of 0.2 m/s0.2 \ m/s. The UFO flies 55 meters above the ground, with a speed of 20 m/s20 \ m/s. The UFO's path is a broken line, where after flying in a straight path of length \ell (in meters) it may turn through for any acute angle α\alpha such that tanα<1000\tan \alpha < \frac{\ell}{1000}. When the UFO's center approaches within 1313 meters of the turtle, it catches the turtle. Prove that for any initial position the UFO can catch the turtle.