“平行四边形的性质”这节课是在学生掌握了平行线、三角形及简单图形的平移和旋转等几何知识的基础上学习的,是这些知识的延续和深化。平行四边形及其性质在实际生产和生活中有广泛的应用,它是本节的重点,又是全章的重点。学习它不仅是对已学平行线、三角形等知识的综合应用和 “The nature of parallelogram ” This lesson is based on the students to learn the parallel geometric knowledge of parallel lines, triangles and simple graphics of the translation and rotation, is the continuation and deepening of these knowledge. Parallelograms and their properties are widely used in actual production and life. It is the focus of this section and the focus of the whole chapter. Learning it is not only a combination of learning parallel lines, triangles and other knowledge