There are many places in the current primary school textbooks that pay attention to the infiltration of extreme thoughts. (1) From the perspective of "quantity", there are multiples of 2 and so on "infinitely many". When teaching the concepts of "natural number", "odd number" and "even number", teachers can make students realize that natural numbers are infinite, and there are also infinite odd numbers and even numbers, so that students can understand the idea of infinity initially.

In the circulating decimal part, 1 ÷ 3 = 0 in teaching. 333… is a cyclic decimal, and the number after the decimal point is endless. ② From the perspective of "graphics", "infinite extensibility" means that two sides of an angle can extend indefinitely. In the teaching of straight lines, rays and parallel lines, let students realize that the two ends of a straight line can extend indefinitely. (3) From the point of view of "method", for example, in the section of "area of circle", the solution of circle area is given: first divide the circle into two equal parts, then divide the two semicircles into several equal parts, and then cut them open to form a figure similar to a rectangle. If the number of copies of a circle is divided equally, the figure will be closer to a rectangle. At this time, the rectangular area is closer to the circular area. The formula for calculating the area of a circle is derived from the area of a triangle, so that students can realize that this is an "infinite approximation" method for calculating the area of a circle. Another example is: Fill in the number 0.9 0.99 0.999 0.9999 ()1/21/411/6 (). Which two numbers are getting closer and closer? Will it be equal to 1 and 0? For another example, consider a triangle as a trapezoid, and the top and bottom are shrinking until it becomes 0 and becomes a point, then the area of the triangle = bottom * height /2.