纵观近几年的高考试题,总存在部分与指数函数、对数函数、幂函数或三角函数有关的图象题,它们大都存在渐近线,而曲线的渐近线是最易被忽略的一个性质.曲线的渐近线是极限思想的直观体现,若能重视这一性质,可借助于自变量x趋于某一个值或趋于无穷时函数值的变化情况来研究图象的形状,从而 Throughout the entrance examination papers in recent years, there are always some of the exponential function, logarithmic function, power function or trigonometric function-related image problems, most of them exist asymptotic lines, and the curve asymptotes are the most easily overlooked One property is that the asymptotic curve of the curve is the direct embodiment of the limit idea. If we can pay attention to this property, we can study the shape of the image by means of the change of the value of the function when the argument x tends to a certain value or tends to infinity, thereby