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近年来中考与圆有关的动态型试题频频出现,已然成为一道亮丽的风景线.而其中相切作为直线(圆)与圆位置关系中的特殊情形,更是中考命题所关注的热点之一.一、一动圆与一定圆相切例1如图1,∠AOB=45°,点O1在OA上,OO1=7,圆O1的半径为2,点O2在射线OB上运动,且圆O2始终与OA相切,当圆O2和圆O1相切时,圆O2的半径
In recent years, the dynamic test of the middle school entrance exam and the circle frequently appear, which has become a beautiful landscape, and the tangent as a special case in the relationship between the line (circle) and the circle is one of the hot spots in the middle school entrance examination. 1, ∠AOB = 45 °, point O1 is on OA, OO1 = 7, radius of circle O1 is 2, point O2 moves on ray OB, and circle O2 is always equal to OA tangent, the radius of circle O2 when circle O2 is tangent to circle O1