导入活动 　　为了庆祝国庆节，我班各小队做了三面三角形彩旗，并都说自己的彩旗面积最大，到底哪个小队做的彩旗面积大呢 ?你能想个方法来判断吗 ?(微机演示 )　　我们先用数方格的方法求三角形的面积。图中每个方格代表 1平方厘米，不满一格的按半格计算，数一数每面三角形 Import activities In order to celebrate the National Day, my class all the teams made a triangular triangle flags, and say their own banners the largest area, in the end which team to do banners large area? Can you think of a way to judge? (Computer demo) We First with a few square method to find the area of ​​the triangle. Each square in the picture represents 1 square centimeter, less than one square is calculated according to a half grid,