Refers to the technical terms often mentioned and used in the stock and futures markets. Generally speaking, the operation time is more than five days.

The three center lines of a triangle always intersect at the same point, which is called the center of gravity of the triangle, and the center line is 2: 1 (vertex to center of gravity: center of gravity to the midpoint of the opposite side).

Double long midline method: double long midline method refers to extending the midline at the bottom to make the extended part equal to the midline, and then it is often necessary to connect the corresponding vertices to make the corresponding angles and sides equal. This method is often used to construct congruent triangles, and the relationship between corresponding edges is proved by the properties of the midline.

The three median lines of an arbitrary triangle divide the triangle into six parts with equal areas. The midline divides the triangle into two parts with equal area. Besides, any other straight line passing through the midpoint will not divide the triangle into two parts with equal area.

In ABC, the center lines of connection angle A, connection angle B and connection angle C are expressed as.

The intersection of the center lines of the triangle is the center of gravity, and the center of gravity line is 2: 1 (vertex to center of gravity: center of gravity to the midpoint of the opposite side).

In a right triangle, the center line corresponding to the right side is half of the hypotenuse.

The midline of a triangle is an important segment in the triangle, and the theorem of the midline of the triangle is an important property theorem. It is the application and deepening of parallel lines, congruent triangles, parallelogram and other knowledge, which is very useful for further study. It is often used to judge the parallelism of two straight lines and demonstrate the overlapping relationship of line segments. In the proof and application of triangle midline theorem, the idea of reduction permeates everywhere, which is an important thinking method.