最新比例尺放大与缩小教学课件教学讲义PPT课件.ppt

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1、比例尺放大与缩小教学课件1、结合具体情境，经历认识图形的放大和缩小，以及把图形放大或缩小的过程。2、理解放大和缩小的含义，能在方格纸上按比例将简单图形放大或缩小。3、积极参加数学活动，获得成功的体验，体会图形的相似，发展空间观念。教学目标同学们，你认识这是什么物体吗？在生活中，你还见过哪些放大与缩小的现象？把一个图形（或物体的图像）放大或缩小后得到的图形（或物体的图像）与原图形（或物体的图像）相比，形状像不同，大小不同。归纳总结分别用同样长的3根、6根和9根小棒摆成三个等边三角形。①②③观察这两个三角形，说一说两个三角形的边有什么关系

2、。第二个三角形的边长是第一个的2倍。第一个三角形的边长是第二个的。12观察这两个三角形，说一说两个三角形的边有什么关系。第一个三角形的边长放大到原来的2倍后得到第二个三角形。第二个三角形的边长缩小到原来的后得到第一个三角形。12第一个三角形和第三个三角形比较，可以怎样说？一个图形无论是放大还是缩小，只是图形的大小发生变化，形状不变，图形中每个角的度数不变。归纳总结在方格纸上按要求画出图形。（1）把下面长方形的各边放大到原来的2倍。放大后的长是3×2＝6个格长，宽是2×2＝4个格长。在方格纸上按要求画出图形。（2）把下面长方形的各边缩小

3、到原来的。12缩小后的长是8×＝4个格长，宽是4×＝2个格长。12121.用小棒摆出下面的图形，使各边缩小到原来的。12shop.99114.com/49610836shop.99114.com/51131153shop.99114.com/51132080shop.99114.com/50668455shop.99114.com/50831388shop.99114.com/51239193shop.99114.com/50673281shop.99114.com/50673437shop.99114.com/50673209sho

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