First, the concept of perimeter:

The length of a closed graph is called perimeter, and the length of a graph is called perimeter. Therefore, the perimeter is equal to the sum of all the edges of the graph. Generally, it is represented by the letter C. If it is a triangle with the same area, the perimeter of an equilateral triangle is the shortest. If you use any polygon with the same area, the circumference of a regular circle is the shortest.

Second, the perimeter formula:

Circle: C=πd=2πr (d is diameter, r is radius, π is pi).

Rectangle: C=2 (a+b)(a is long and b is wide).

Circumference of triangle: C=a+b+c (abc is three sides of triangle).

The circumference of the sector: c = 2r+nπ r ÷ 180 (n = central angle) =2R+kR (k= radian).

Formula of trapezoid perimeter: C= upper bottom+lower bottom+two waist lengths.

The circumference formula of isosceles trapezoid: C= upper bottom+lower bottom +2 waist.

Five applications of perimeter

1, geometry:

In geometry, perimeter is an important index to study the properties of graphics. For example, when calculating the area difference between two graphs, it is usually necessary to calculate their perimeters first. In addition, the perimeter can also be used to judge whether a figure meets certain conditions, such as whether a triangle is an equilateral triangle.

2, engineering design:

In engineering design, perimeter is one of the important parameters to determine the shape and size of an object. For example, when designing a building, designers need to consider the perimeter of the building to determine its shape and size. At the same time, the perimeter is also an important basis for calculating the material requirements (such as steel, glass, etc.). ).

3, computer graphics:

In computer graphics, perimeter is used to represent the length of graphic boundary. For example, when drawing a rectangle or a circle, the computer needs to calculate its perimeter. In addition, the perimeter is also an important parameter to calculate the image size and resolution.

4. Measurement:

In surveying, the perimeter is used to represent the boundary length of the plot. For example, when measuring the area of a piece of land, the surveyor needs to calculate its perimeter first. At the same time, the perimeter is also an important parameter to calculate the environmental changes around the plot.

5, biomedical engineering:

In biomedical engineering, perimeter is used to indicate the length of blood vessels or other biological tissues.