在小学六年的数学学习中,教师常常会帮助学生从纷繁复杂的数学现实中,提炼出简练精辟的定义、性质、公式和法则。例如:定义:围绕平面封闭图形边界一周的线段的长度叫做这个图形的周长;含有未知数的等式是方程;性质:直线没有端点,可以向两边延伸;射线有一个端点,可以 In the six years of primary school mathematics, teachers often help students to extract concise and ingenious definitions, properties, formulas and rules from the complicated mathematical reality. For example: Definition: The length of a line around the boundary of a figure enclosing the boundary of a figure is called the perimeter of this figure; the equation with unknowns is an equation; Properties: Straight lines have no endpoints and can extend to both sides; rays have an endpoint that can