当我写下这个话题时,自己也吃了一惊。其实,很早之前我就有过这样的朦胧想法,但真正促成动笔成文的还是源于不久前与一位老师的对话。这位老师是市级数学学科带头人,最近他要执教市级公开课,选择的课题是“多边形内角和”。试教时遵循由易到难、由特殊到一般的原则,从 When I wrote this topic, I was also taken aback. Actually, I had such a vague idea long ago, but what really contributed to writing was a dialogue with a teacher not long ago. The teacher is a municipal mathematics leader, and he recently coached the municipal open class. The subject of his choice was “Polygonal Inner Corner and ”. Trying to follow from easy to difficult, from the special to the general principle, from