四边形知识是平行线、三角形知识的应用和深化,经常与三角形、相似三角形知识相综合,是中考必考内容.主要学习特殊的四边形--平行四边形、矩形、菱形、正方形及梯形的有关知识及其应用,并由此进一步研究平行线等分线段定理、三角形和梯形的中位线定理、中心对称图形的定义、性质.要掌握研究多边形问题的方法--将多边形转化为三角 The quadrilateral knowledge is the application and deepening of the knowledge of parallel lines and triangles. It is often combined with knowledge of triangles and similar triangles. It is a necessary part of the examination. It mainly studies the special quadrilaterals--parallelograms, rectangles, diamonds, squares and trapezoids. Its application, and thus further study of the parallel line bisector theorem, triangle and trapezoidal median line theorem, the definition and nature of the center symmetrical figure. To master the method of studying the polygon problem - convert the polygon into a triangle