1. First, know three numbers. The width and height of the overall shape of the three figures are the same.

2. The convex is as long as the periphery of the mouth, as shown in the figure below. Move the shoulder line segments AB, CD and line segments of the convex figure upward to EF, and then move the BE and CF line segments to both sides to the side width, and you can know that the convex is as long as the periphery of the mouth.

3. The periphery of the concave pattern is longer than that of the mouth pattern. As shown in the figure below, move the AB line segment of the concave pattern upward to CD, which is equivalent to the periphery of the mouth pattern, so the periphery of the concave pattern is longer than that of the mouth pattern.

Extended data commonly used graphics perimeter formula:

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

2. The perimeter of the triangle is C = a+b+c(abc is three sides of the triangle).

3. Quadrilateral: C=a+b+c+d(abcd is the side length of quadrilateral)

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