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北师大版《数学》实验教材第一章《丰富的图形世界》第三节《截一个几何体》中,设计了几个切截几何体的实验活动。 亲身经历切截几何体,可以帮助我们认识到;用不同的方法去截同一个几何体,它的截面形状、截面大小是不同的;所有的几何体通过切截,都可以切成许多的“薄片”,进一步体会到“面动成体”的规律。 下面,向同学们介绍怎样从正方体中切截出预定的三角形、四边形的截面。
In the third chapter of the “Graphic World” section of the experimental textbook “Mathematics” of Beijing Normal University, “Section One Geometry”, several experimental activities for cutting geometry were designed. The experience of cutting geometry in person can help us realize that different shapes can be used to cut the same geometry. Its cross-sectional shape and cross-sectional size are different; all geometric shapes can be cut into many “slices” by cutting. Further understand the law of “face-moving adults.” Next, we will introduce to students how to cut out the predetermined triangular and quadrangular cross sections from the cube.