前言:我們(筆者)關於“極限”的學習,雖然是在不同的时期,但是在学习过程中,曾發生些共同的問題,我們願意將問題及發生的原因寫出来,然后將现在對於它的看法及教法提出来,供教師及同學們參考,我們歡迎批評,希望直接或间接的對於教学和教法上有些貢献. Foreword: Although we (the author) learn about “limits”, although they are in different periods, some common problems have occurred in the learning process. We are willing to write out the problems and the reasons for the occurrence, and then we will now deal with them. The views and teachings are proposed for reference by teachers and classmates. We welcome criticism and hope to directly or indirectly contribute to teaching and teaching.