在几何问题中,巧妙地运用旋转法去解题,有时可以起到很好的效果.一、求线段的长例1如图1,在四边形ABCD中,AB=BC,∠ABC=∠CDA=90°,BE⊥AD于E,S四边形ABCD=8,求DE的长.分析图中四边形是任意四边形,直接求解不容易,但是,题中有条件AB=BC,且∠ABC=90°,所以如果把ABE绕点B按逆时针 In the geometric problem, clever use of the rotation method to solve the problem, sometimes can play a very good effect. First, to find a long example of the line 1 In Figure 1, in the quadrilateral ABCD, AB = BC, ∠ ABC = ∠ CDA = 90°, BE⊥AD in E,S quadrilateral ABCD=8, find the length of DE. In the analysis graph, the quadrilateral is an arbitrary quadrilateral, and the direct solution is not easy, but the condition is AB=BC, and ∠ABC=90°. So if you place ABE around point B counterclockwise