G·波利亚在《怎样解题》一文中指出:“题目一旦获解,就立刻产生情感上的满足,恰好错过了提高的机会.事实上,没有一道题可以解决得十全十美,总会剩下一些工作要做.经过充分的探讨与总结,我们总会有新的发现,而且在多数情况下,都能提高自己对这个问题的认识.”引例(西宁)如图1,已知正方形ABCD的边长为3,E、F分别是AB、BC边上的点,且∠EDF=45°,将△DAE绕点D逆时针旋转90°,得到△DCM.若AE= G. Polia pointed out in the article entitled “How to Solve Problems”: “Once the subject is solved, there is an immediate emotional satisfaction that just missed the opportunity for improvement. In fact, there is no single problem that can be solved perfectly, After some work to be done, after thorough discussion and conclusion, we will always find new discoveries, and in most cases, we will be able to raise our awareness of the issue. ”The example (Xining) is known as Figure 1 The side length of the square ABCD is 3, and E and F are the points on the edges of AB and BC, respectively, and ∠ EDF = 45 °, and ΔDAE is rotated by 90 ° counterclockwise about point D to obtain ΔDEC. If AE =