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在近几年的中考中,常出现一些以特殊的四边形为载体,将三角板绕着它的某一点旋转的动态问题.它们将三角板与四边形的知识巧妙地联系在一起.现把几道中考试题改编后加以分析,供同学们参考.一、探求旋转过程中的不变数量例1(江苏泰州中考题改编)如图1,正方形ABCD的对角线相交于点O,将直角三角板的直角顶点与O点重合,转动三角板使两直角边始终与BC、AB相交,交点分别为M、N.
In the middle school entrance examinations of recent years, there are often some dynamic problems of rotating the triangle plate around a certain point with a special quadrilateral as the carrier, which skillfully links the triangle plate with the quadrilateral knowledge. First, explore the invariant number of rotation process Example 1 (Jiangsu Taizhou entrance exam questions) Figure 1, the diagonal intersection of the square ABCD at point O, the right angle vertices Coincides with the O point, turn the triangle so that the two right-angle edges always intersect BC, AB, the intersection points were M, N.