把一个图形绕着某一个点O转动一个角度后得另一图形的变换叫做旋转,点O叫做旋转中心,转动的角叫做旋转角。解题中会常用到旋转的一重要性质:旋转前后的图形全等。这样,许多不易推证全等的两个图形,只要通过旋转就会简化过程。特别是有关正三角形、等腰三角形、正方形一类的问题的求解、证明尤其是这样,现举例如下: Rotating a figure around a certain point O to obtain another figure is called rotation. Point O is called rotation center, and the angle of rotation is called rotation angle. One important property of rotation is often used in the problem solving: graphics before and after rotation are all equal. In this way, many of the two figures that are not easy to certify as a whole will only have to simplify the process by rotating them. In particular, the solution to the problems involving isosceles triangles, isosceles triangles, and squares, and the proof is especially true. Here are some examples: