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圆是既是轴对称图形,又是中心对称图形,由于它的这种特殊性,圆中存在许多两解问题,解答时要善于挖掘题目的所给条件,分多种情况,逐一讨论解决,现举例说明圆中的两解问题,以供同学们参考。一、点与圆的位置关系问题例1已知点P到圆上的点最大距离是9㎝,最小距离是3㎝,则⊙O的半径是cm.A.6㎝B.3㎝C.6㎝或3㎝D.9㎝.【分析】本题未指明点P与⊙O的位置关系,显然点P不可能在⊙O上,因此,应分点P在⊙O内或点P在⊙O外两种情况来考虑.
Because of its special nature, the circle is both an axisymmetric figure and a centrosymmetric figure. Because of its particularity, there are many solutions to the problem in the circle. When solving a problem, Give an example of two problems in the circle, for the students to refer to. First, the relationship between the point and the circle Problem Example 1 Known point P to the point on the circle the maximum distance is 9 ㎝, the minimum distance is 3 ㎝, the radius of ⊙ O is cm.A.6 ㎝ B.3 ㎝ C. 6 ㎝ or 3 ㎝ D.9 ㎝. [Analysis] This question does not specify the location of point P and ⊙ O, obviously P can not be in ⊙ O, therefore, should be points P in ⊙ O or point P in ⊙ O outside the two situations to consider.