周期函数是中学数学学习中的一个难点.现行的高中数学教材是从正弦函数值、余弦函数值按一定规律不断重复这一性质引出的,并没有对周期函数相关问题进行较为系统的分析、讨论,不少同学对周期函数概念的理解比较模糊,经常出现各种错误解答.下文给出几点说明供参考. The periodic function is a difficult point in the study of middle school mathematics. The current high school mathematics textbooks are derived from the constant repetition of the sine function value and the cosine function value according to a certain rule. There is no systematic analysis and discussion of the periodic function related problems. Many students have a rather ambiguous understanding of the concept of the periodic function, and often have various wrong answers. Here are some explanations for reference.