三垂线定理(及其逆定理,以下同)是立体几何中很重要的定理。它沟通了空间的直线与直线及直线与平面这两类位置关系之间的联系,表达了平面与空间不同范围内问题的互相转化的规律,同时这个定理应用广泛,解决的问题较多。现就这个定理的教学,谈一些粗浅看法。 The triple vertical theorem (and its inverse theorem, the same below) is a very important theorem in solid geometry. It communicates the relationship between the straight lines and straight lines of space and the positional relationships between straight lines and planes. It expresses the law of mutual transformation of problems in different planes and spaces. At the same time, the theorem is widely used to solve many problems. Let’s talk about some superficial views on the teaching of this theorem.