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题目:(全国新课标2文科第12题)设点M(x0,1),若在圆O:x2+y2=1上存在点N,使得∠OMN=45°,则x0的取值范围是(原题是选择题)分析:圆的问题,首先想到几何法,抓圆心,半径,切点之类的几何性质解题.圆有关问题在高考中经常被考查,属于重点难点.此题也是可以简单地转化到圆心,利用最大角大于或等于45°,即存在这样的角即可.图1解:如图1,当MN与圆相切时,
Subject: (National New Curriculum 2 liberal arts Question 12) set point M (x0,1), if the circle O: x2 + y2 = 1 there is a point N, so ∠ OMN = 45 °, the range of x0 Is the original question is the multiple-choice questions Analysis: Round questions, first of all think of geometry, grasping the center of the circle, radius, tangent point of the geometric nature of the problem solving. Round of the relevant issues in the college entrance examination is often examined, are the key challenges. Can also be simply converted to the center of the circle, using the maximum angle greater than or equal to 45 °, that is, there is such an angle Figure 1 Solution: Figure 1, when the MN tangent to the circle,