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近年来,范围与最值问题是高考的热点,也是难点.有的题,学生是有思路,但是方法选的不好,导致解不出来;有的题,学生是根本无从下手,尤其是以圆为载体与存在、恒成立问题综合的题目.鉴于此,我把平时积累的此类问题做了一番整理.例1如图1,已知圆M:(x-1)~2+(y-1)~2=4,直线l:x+y-6=0,A为直线l上一点.若圆M上存在两点B,C,使∠BAC=60°,则A点横坐标的
In recent years, the scope and value of the most important issue is a hot college entrance examination, but also difficult. Some questions, students have ideas, but the method selected poor, leading to unsolvable; some questions, students simply can not start, especially in order to As a carrier and the existence of the circle, the problem of the establishment of a comprehensive problem. In view of this, I usually do some sort of accumulation of these problems. Example 1 In Figure 1, known circle M: (x-1) ~ 2 + ( If there are two points B and C on the circle M such that ∠BAC = 60 °, then the abscissa of point A of