2.l stands for arc length and is also used to represent chord length. 3.s stands for area. 4.v stands for surplus products. The length integral of the edge around a finite area is called the perimeter, which is the length of a graph.

The circumference is represented by the letter C. Let the upper bottom length of the trapezoid be A, the lower bottom length be B, the two waist lengths be E and D respectively, and the circumference be C. Then the formula of the circumference of the trapezoid is C=a+b+c+d, which is usually represented as: upper bottom+lower bottom+waist+waist. Calculation formula of perimeter: circle: c = π d = 2π r (d is diameter, r is radius, π) The perimeter of a triangle is c = a+b+c (ABC is three sides of the triangle). Quadrilateral: c = a+b+c+d (ABCD is the side length of quadrilateral). Special: rectangle: c = 2 (a+b) (a is long and b is wide) square: c = 4a (a is the side length of a square).

Polygon: c = sum of all sides.

The circumference of the sector: c = 2r+nπ r ÷ 180 _ (n = central angle) = 2r+kr (k = radian). The circumference of the earth was first calculated in the history of circumference: Eratosthenes in ancient Greece calculated the circumference of the earth with simple measuring tools more than 2,000 years ago.