The length integral of edges around a finite area is called perimeter, and the length of a graph is the perimeter of the graph. Therefore, the perimeter is equal to the sum of all the edges of the graph.

Commonly used formula:

1, triangle (general triangle, Helen formula)

Perimeter L = A+B+C (A, b and c are the lengths of three sides of a triangle, the same below).

Area S = √[p(p-a)(p-b)(p-c)], p = (1/2)(a+b+c).

2. Rectangular

Perimeter l = 2 (a+b) (a and b are the lengths of adjacent sides of a rectangle, the same below).

Area S = ab

Step 3 square

Circumference L = 4a

Area S = a^2

4, trapezoidal

Circumference L = a+b+c+d(a: upper sole, b: lower sole, length of c and d waist, the same below).

Area S = (1/2)(a+b)h(h: height of trapezoid)

5. circle

Perimeter L = 2πr(π:π, r: radius of circle, the same below)

Area S = πr^2