极限思想作为数学思想方法之一，为教师们所熟知，但对于中学生（包括师范生），由于较多接触的是有限量，或有限变化过程的量的问题，形成了思维定势，即使学习了极限概念，极限意识仍然淡薄，极限思想难以应用；如讲完数列极限后，有学生提出：“０．９·是否等于１？”围绕 Extreme thinking is one of the mathematical thinking methods known to teachers, but for middle school students (including normal students), due to the limited number of exposures, or the problem of limited changes in the process, the mindset is formed, even if the learning With the concept of limit, the consciousness of extremes is still weak, and the idea of ​​limit is difficult to apply. After finishing the series of limits, some students put forward: “Does 0.9 equals 1?”