从有理数到实数,是人类对“数”的认识的一个巨大飞跃,其中无理数槡2的发现功不可没.“2有多大”是人教版八年级上册中的内容,引导学生认识“2有多大”既能够帮助学生建立无理数的概念,也有助于建立学生的数感.理解数感、让学生在数学学习过程中建立数感,是数学课程标准十分强调和重视的问题.所谓数感, From rational numbers to real numbers, is a huge leap in human understanding of “number ”, of which the discovery of irrational number 槡 2 “2 is how much ” is the PEP eighth grade volumes in the content to guide students Knowing how much “2” can not only help students to establish the concept of irrational number, but also help to establish the sense of number of students. Understanding the sense of number and letting students build a sense of number in math learning process are very emphasized and valued by the math curriculum standard The problem. The so-called number sense,