“四龟问题”是一个古老而又传统的问题.例1如图1,在边长为3m的正方形ABCD的四顶点各有一只小乌龟,代号依次为1、2、3、4,从某时刻开始,它们同时以1cm/s的速度匀速追赶与其相邻的一只乌龟,运动方向始终指向被追赶的乌龟,追赶方向分别为:1号追2号,2号追3号,3号追4号,4号追1号.问:经过多长时间它们同时相遇?分析正方形是成90°旋转的对称图形.由于四乌龟开始处于正方形的四个顶点上,它们的运动速度又相同,所以,在它们按题目要求的运动方式追赶过程中的任一时刻,四个乌龟所在的四个点组成 Example 1 As shown in Fig. 1, a small turtle at four vertices of a square ABCD with a side length of 3m each has a code of 1, 2, 3, 4, At a certain time, they also catch a turtle at a constant speed of 1 cm / s at the same time. The direction of the movement always points to the turtle being chased. The direction of chase is: chase no. 2, chase no. 3, no.3 No. 4, No. 1, No. 4. Q: After how long they meet together? Analysis of the square is a 90 ° rotation of the symmetrical figure. Since the four turtles began in the square of the four vertices, and their movement speed are the same , So at any point in the process of pursuing the sport they require by the subject, the four points where the four turtles are located form