概念位于三角形的各边上，且将周长两等分的点叫周界中点，顶点和周界中点的连线叫周界中线，三条周界中线交于一点，这点叫三角形的界心．大家知道欧拉线，即三角形的垂心、重心和外心共线，且重心到垂心的距离等于重心到外心距离的两倍，与此极其相似的是定理三角形的界心、 The concept is located on each side of the triangle, and the point where the perimeter is bisected is called the midpoint of the perimeter. The connection between the vertex and the midpoint of the perimeter is called the perimeter centerline, and the perimeter of the three perimeters intersects at one point. This is called the boundary of the triangle. Everyone knows that the Euler line, which is the triangle’s center of gravity, center of gravity, and external line, and that the distance from the center of gravity to the center of divination is equal to twice the distance from the center of gravity to the center of the heart, is very similar to the circle of the theorem triangle.