曲线的切线是学习较早,应用较多,中考,高考命题频率较高的知识点之一.从《平面几何》中圆的切线、《解析几何》中圆锥曲线的切线、到应用导数求曲线的切线,由特殊到一般,由低级到高级,步步深入.然而在学习过程中,老师、学生对各阶段切线知识的认 The tangent of the curve is one of the knowledge points for learning earlier, applying more, taking the exam, and having a higher frequency of the college entrance examination proposition. From the tangent of the circle in “Planar Geometry”, the tangent of the conic curve in “Analysis Geometry” to the application of derivative to the curve The tangent line from special to general, from low level to high level, step by step. However, in the learning process, teachers and students recognize the tangent knowledge at each stage.