"game" on the plane
Source: 2022 China Southeast Grade 10/11 P8
August 3, 2022
combinatoricswinning strategy
Problem Statement
Tao plays the following game:given a constant ;for any positive integer ,the time between the round and the round of the game is seconds;Tao chooses a circular safe area whose radius is (with the border,and the choosing time won't be calculated) on the plane in the round;the chosen circular safe area in each round will keep its center fixed,and its radius will decrease at the speed in the rest of the time(if the radius decreases to ,erase the circular safe area);if it's possible to choose a circular safe area inside the union of the rest safe areas sometime before the round(including the round),then Tao wins the game.If Tao has a winning strategy,find the minimum value of .