函数的单调性是高中数学的核心概念之一,笔者不止一次上过函数单调性的概念课,也曾多次在各种场合听过本节课,但是也总听到学生不断地问函数单调性的定义中为什么要设x1,x2,怎么想到设x1,x2等问题.这便是概念的形成、抽象过程中的自然性、合理性问题,在概念的形成过程中,每一个符号的出现都应具有它的合理性,每一步的抽象都应具有它的自然性,而不是生搬硬套、突兀地强加给学生.笔者认为,这在概念的新授课中是至关重要的,这 The monotonicity of the function is one of the core concepts of high school mathematics. The author has noticed the concept class of the monotonicity of functions more than once. He has also heard this lesson many times in various occasions, but he also always heard students constantly asking monotony Why x1, x2 in sex definition, how to think about x1, x2, etc. This is the formation of concept, the naturalness and rationality of abstract process, and the appearance of each symbol in the formation of concept Should have its rationality, the abstraction of each step should have its natural, rather than mechanically, implicitly imposing on students.I think, this is the concept of new lectures is crucial, which