编者按 :这是一堂学生活动较多的学习讨论课 .如何由正弦函数、余弦函数的性质来学习正切、余切函数的图象和性质 ,本节课采用由学生从对比中自己提出问题 ,自己设计问题的设计思路是有新意的 .这节课总体上看是较成功的 .比教师平淡地“照本宣科”的教法效果更好 .好在教师正 Editor’s note: This is a learning discussion class with more student activities. How to learn the tangent and cotangent function images and properties from the nature of the sine function and the cosine function. In this lesson, students are asked to ask questions from the comparison. The design idea of ​​the design problem of my own is a new idea. This class is generally more successful. It is better than the teacher’s teaching method of “pronounced script”. Fortunately, the teacher is positive.