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为了巩固圆的面积计算知识,老师出了这样一道题:“正方形的面积是40平方厘米,求阴影部分的面积(如图)”(?)学生初看题目,都认为好做,只要在正方形里减去这个圆面积的1/4就行了。真要动笔,却被难住了:求1/4圆的面积先要知道这个圆的半径,而已知条件是正方形的面积,要从中求出边长,小学生还没学过。于是师生间进行了如下的谈话:“求圆的面积的计算公式你们都知道吗?”
In order to consolidate the calculation of the area of the circle, the teacher came up with such a question: “The square area is 40 square centimeters, the area of shading (Figure)” (?) Students first look at the title, do think that as long as the square In the subtraction of the circular area of 1/4 on the line. Really want to write, but was stumped: find a quarter of the area must first know the radius of the circle, and the known conditions are square area, to find the side length, the pupils have not learned. As a result, the teachers and students talked about the following: "Do you know the formula of calculating the area?