一、问题背景在南京市的一次模拟考试中,一道直线与圆相交的问题引发了笔者对高三复习教学中的一些思考.题目在平面直角坐标系xOy中,过点P(5,3)作直线l与圆x2+y2=1相交于A,B两点.若OA⊥OB,则直线l的斜率为.由考后的统计数据知该题的难度系数为0.49,均分为2.47,略低于全卷的难度系数0.51.该题实际上是课本一道例题的简单变 First, the problem background In a simulation test in Nanjing, a straight line intersect with the circle led to the author of the Refresher Teaching Review some of the topics in Cartesian coordinate system xOy, over point P (5,3) for Line l and the circle x2 + y2 = 1 intersect at A, B. If OA ⊥ OB, then the slope of the straight line l. After examination of the statistical data that the difficulty of the question is 0.49, is divided into 2.47, slightly Less than the full volume of the difficulty coefficient of 0.51. The question is actually a simple example of the textbook changes