选入课本的习题大多比较经典,因此具有很好的探究价值,很多竞赛题就是以这些课本习题为基础编拟出来的.因此,不论是进行中考复习还是进行竞赛培训,如果能对课本习题予以很好的探究与挖掘,一定能收到很好的效果.如右图,一张锐角三角形的硬纸片,AD是BC上的高,BC=30cm,AD=20cm,从这张硬纸片上剪下一个正方形EFGH,使它的一 Most of the exercises for textbook selection are quite classic, so it has good exploration value. Many competition questions are compiled based on these textbook exercises. Therefore, whether it is a mid-level exam or a competition training, if you can give textbook exercises Good exploration and mining, will be able to receive very good results.As shown on the right, an acute triangle triangular piece of paper, AD is BC on the high, BC = 30cm, AD = 20cm, from this piece of cardboard Cut a square EFGH and make it one