Perimeter c, the integral of the perimeter of the edge of a finite area, is called perimeter and is the length of a graph. The perimeter of a polygon is also equal to the sum of all sides of a graph, the perimeter of a circle =πd=2πr (d is the diameter, R is the radius, π), and the perimeter of a sector = 2R+nπR÷ 180? (n= central angle) = 2R+kR (k= radian).

Area S. When the space occupied by an object is a two-dimensional space, the size of the occupied space is called the area of the object, which can be plane or curved. Square meters, square decimeters and square centimeters are recognized units of area and can be expressed as (m? ，dm？ ，cm？ )。

Area is a quantity indicating the degree of a two-dimensional figure or shape or plane layer in a plane. A surface region is a simulation on a two-dimensional surface of a three-dimensional object. Area can be understood as the amount of material with a given thickness, which is necessary to form a shape model.

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Area bisector

There are countless lines bisecting the triangle area. Three of them are the median of the triangle (connecting the midpoint of both sides and the opposite vertex), and they are collinear at the center of gravity of the triangle; ?

In fact, they are the only area bisectors passing through the center of gravity. Any line that divides the area and perimeter of a triangle into two halves can pass through the entrance of the triangle (the center of its perimeter). For any given triangle, there are one, two or three triangles.

Any line passing through the midpoint of the parallelogram divides the area in two. All bisectors of the area of a circle or other ellipse pass through the center, and any chord passing through the center bisects the area. For circles, they are the diameter of the circle.

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