Perimeter - the total length of the border of the figure (most often on the plane). It has the same dimension as the length. Sometimes the border of a geometric figure is called the perimeter. Perimeter calculation is of practical importance. The formulas for the perimeters of all the main figures are a triangle, a rectangle, a trapezoid, a circle length, an arc length.

Content:
- Circle perimeter or circumference
- Arc length
- The perimeter of the triangle
- The perimeter of the rectangle
- The perimeter of the square
- The parallelogram perimeter
- The perimeter of the rhombus
- trapezoid perimeter
- Arc length, Huygens formula