在数学命题中,经常出现“有一个”、“只有一个”的提法。学生初次接触,往往对于两者的含义理解不清。混为一谈。对此,我们可以通过一些实例来加以说明和比较,从中来理解“有一个”与“只有一个”本质上的区别。例如 (1)某班有一个女同学身高1.75米。 (2)某班只有一个女同学身高1.75米。 (1)说的是这个女同学的身高1.75米,与班内其他女同学的身高无关,即允许下面两种情况之一 In mathematical propositions, there are often “one” and “only one” references. Students first contact, often for the meaning of the two unclear. Confused. In this regard, we can use some examples to illustrate and compare, to understand the “one” and “only one” essential difference. For example (1) a classmate has a female student height 1.75 meters. (2) a class only a female student height 1.75 meters. (1) said that the female student's height of 1.75 meters, regardless of class and other female students height, which allows one of the following two conditions