(1) Through observation and comparison, we can intuitively understand the characteristics of quadrangles, and use the characteristics to distinguish which graphics are quadrangles.

(2) Can draw quadrangles on point drawing or grid paper, and can circle quadrangles on nail board.

2, parallelogram:

(1) Based on the life situation, we can initially perceive the characteristics of parallelograms and distinguish which graphics are parallelograms.

(2) You can draw a parallelogram on a bitmap or grid paper, or circle a parallelogram on the nail board.

(3) The connection and difference between the penetrating parallelogram and the rectangle.

3. Perimeter:

(1) Understand and accurately grasp the concept of perimeter by combining specific objects and figures, and can describe the perimeter of a given figure in mathematical language.

(2) The perimeter of a given graph can be measured or calculated by different methods, and the perimeters of two graphs can be compared.

4. Perimeter of rectangle and square:

(1) Explore and master the calculation method of the perimeter of rectangle and square, and feel the application of mathematics in life.

(2) Be able to choose appropriate methods, skillfully calculate the perimeters of rectangles and squares, and solve related practical problems in specific situations.

5. Estimation: (1) On the premise of accurately grasping the length unit, the length (including circumference) of a line segment or object can be reasonably and appropriately estimated. (2) Be able to use the estimated knowledge to solve practical problems in life.