以圆为载体的最值问题是近几年中考热点考题之一,这类题新颖、独特,综合性强,有利于培养同学们的学习兴趣,对提高同学们的解题能力也大有益处.现精选几例如下,供参考.一、最长线段例1如图1,某数学兴趣小组,利用树影测量树高.已测出树AB的影长AC为9米,并测出此时太阳光线与地面成30°夹角.(1)求出树高AB;(2)因水土流失,此时树AB沿太阳光线方向倒下,在倾倒过程中,树影长度发生了变 The circle as the carrier of the most value issue is one of the hottest entrance exams in recent years, such questions are novel, unique, comprehensive, conducive to cultivating students ’interest in learning, to improve students’ ability to solve problems is also beneficial Now select a few examples below, for reference .A, the longest line segment Example 1 Figure 1, a mathematical interest group, the use of tree shadow measurement tree height has been measured AB tree shadow length AC 9 meters, and measured (1) Calculate the height AB of the tree; (2) Because of soil erosion, the trees AB fall along the sun’s rays at this time, and the tree shadow length changes during the dumping process