“设”是数学解题过程中经常采用的重要措施之一·正是因为有了“设”,才架起了由此到彼的桥梁,实现了由复杂到简单的转化,从而步入了由未知到已知的坦途.同时,“设”又是一把双刃剑·设得好,则效果显著,事半功倍;否则,不仅无助于解题,而且还容易造成“错而不觉,劳而无功”的结 “Design” is one of the important measures often used in the process of solving problems in mathematics. It is precisely because of the “design” that the bridge from one to the other is erected, and the transformation from complexity to simplicity is achieved. From the unknown to the known way. At the same time, “design” is a double-edged sword. If you set it well, the effect will be significant and you will get twice the result with half the effort. Otherwise, it will not only help solve the problem, but it will also lead to “wrong feelings”. The knot of vain and vain