First of all, a brief introduction.
1, the perimeter of the rectangle = (length+width) ×2, and c = (a+b) × 2; Circumference of a square = side length ×4, area of a rectangle = length × width, area of a square = side length × side length, S=a.a=, a.
2. Area of triangle = base × height ÷2, s = ah ÷ 2; Area of parallelogram = bottom× height s = ah trapezoid area = (upper bottom+lower bottom) × height ÷2, and s = (a+b) h ÷ 2.
Second, the perimeter
1, the integral of the length of the edges 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 sides of a graph, the perimeter of a circle =πd=2πr(d is the diameter, R is the radius, π), and the perimeter of a sector =2R+nπR÷ 180? (n= central angle) =2R+kR(k= radian).
2. The integral of the length of the edge around a finite area is called the perimeter, which is the length of a graph. The circumference is indicated by the letter C.
Third, the area and perimeter.
1, 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.
2. Perimeter can only be used on two-dimensional graphics (plane and surface), and three-dimensional graphics (solid) such as cylinder, cone and sphere can't express their boundary size with perimeter, but with total surface area. Total surface area = the total area of all sides of a solid. "Understanding of perimeter" is the learning content of the third grade of compulsory education mathematics (Volume I).
3. 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 Perimeter in real life; Secondly, let students master the method and process of measuring circumference; Finally, experience and feel the application of mathematics in life.