由于圆心到圆的切割线的距离总是等于或小于圆的半径,于是得到一个不等关系.依此,我们将一类函数、方程中的问题转化为圆心到圆的切割线距离问题,从而使问题顺利得到解决.下面列举几例阐述,供读者参考.例1若点P(x,y)的坐标满足方程xcosα+ysinα-4=0,则当角α在实数范围内变化时, Since the distance from the center of the circle to the circle’s cutting line is always equal to or less than the radius of the circle, we get an unequal relationship. Thus, we convert the problems in a class of functions and equations into the distance from the circle center to the circle, So that the problem is solved smoothly. The following is a few examples for readers reference. Example 1 If the point P (x, y) coordinates satisfy the equation xcosα + ysinα-4 = 0, then when the angle α in the real range of changes,