知识要点熟悉有关多边形的概念与性质;掌握平行四边形(包括矩形、萎形、正方形)的概念,性质和判定;掌握梯形的概念,等腰梯形的性质和判定;掌握平行线等分线段定理及三角形、梯形中位线定理;理解中心对称图形的概念,了解面积的概念,掌握矩形、三角形、平行四边形和梯形的面积公式,会用割补法计算一些简单的复合图形的面积;了解三角形与四边形的等积变形。掌握勾股定理,能熟练地用勾股定理进行有关的计算和证明,会用勾股定理的逆定理判断一个三角形是不是直角三角形。能够直接根据定义和定理作出(画出)平行四边 Knowledge points are familiar with the concept and nature of polygons; master the concepts, properties, and judgments of parallelograms (including rectangles, wilts, and squares); grasp the concept of trapezoids, the nature and determination of isosceles trapezoids; and master the theorem of bisectors of parallel lines and Triangle, trapezoidal median line theorem; understand the concept of central symmetry, understand the concept of area, grasp the area formulae of rectangles, triangles, parallelograms, and trapezoids, and calculate the area of ​​some simple composite graphs using the trimming method; Quadrilateral equal product distortion. Mastering the Pythagorean theorem, skilled in the use of the Pythagorean theorem to carry out the relevant calculations and proofs, will use the inverse theorem of the Pythagorean theorem to determine whether a triangle is a right-angled triangle. Ability to make (drawing) parallelograms directly based on definitions and theorems