在立体几何教学中经常出现求最值问题,其中采用“折叠”与“展开”求最值是这类问题的难点之一.在此,想用下面几个例题来分析这类问题.一、在旋转体中如何展开求其表面上的最短距离例1圆柱的轴截面是边长为5 cm的正方形ABCD,求圆柱侧面上从A点到C点的最短距离.分析曲面上的最短距离AC与侧面展开图中的A,C两点间距离相等.解把圆柱沿母线CD剪开后展开在平 In the three-dimensional geometry teaching, we often find the most value problem, among which “folding ” and “expanding ” find the most value is one of the difficulties of this kind of problem. Problem 1. How to find the shortest distance on the surface in a rotating body Example 1 The axis of a cylinder is a square ABCD with a side length of 5 cm and find the shortest distance from the A point to the C point on the side of the cylinder. The shortest distance between AC and the side of the expansion in Figure A, C, the distance between the two points equal to the solution of the cylinder along the bus CD cut open flat