Specific content:

Circle: C=πd=2πr(d diameter, R radius); Triangle: C=a+b+c(abc is three sides); Quadrilateral: C=a+b+c+d(abcd is the side length of quadrilateral); Rectangular: C=2*(a+b)(ab is the length and width); Square: C=4*a(a is the side length of the square); Sector: c = 2r+nπ r ÷ 180 = 2r+kr (k radians).

Perimeter introduction:

The length integral of the edge around a finite area is called the perimeter, which is the length of a graph. The perimeter of a polygon is also equal to the sum of all the edges of the graph.

Area and perimeter:

If it is a triangle with the same area, the perimeter of an equilateral triangle is the shortest; If it is a quadrilateral with the same area, the perimeter of the square is the shortest; If pentagons with the same area are used, the perimeter of regular pentagons is the shortest; If you use any polygon with the same area, the circumference of a regular circle is the shortest.

Perimeter can only be used on two-dimensional figures (planes and surfaces), and three-dimensional figures (solids) such as cylinders, cones and spheres can't express their boundary size by perimeter, but by total surface area.

Perimeter-related teaching:

1, content standard

The understanding of perimeter is the learning content of the third grade in the first phase of compulsory education mathematics (Volume I). The learning content of "understanding of perimeter" in the curriculum standard actually includes three levels: first, let students know the concept of perimeter and experience it in real life; Secondly, let students master the method and process of measuring circumference; Finally, the application of empirical mathematics in life.

2. Course objectives

The curriculum standard clearly points out the target requirement of "knowing the perimeter", that is, "pointing out and measuring the perimeter of specific figures, exploring and mastering the perimeter formulas of rectangles and squares". In addition, in the overall goal of mathematics curriculum, it is also the goal requirement of "knowing the perimeter" to gain some preliminary experience in mathematics practice.

The course objectives here are actually the refinement and concrete embodiment of knowledge and skills, mathematical thinking, problem solving and emotional attitude objectives. Feel the close connection between mathematics and daily life. Rationality of mathematical thinking processes such as observation, operation and induction. Under the guidance of others, mistakes in mathematical activities can be found and corrected in time.