Half-angle model refers to a basic plane geometric model, which consists of two rays that form an angle of 45 with a vertex of a square, and their intersection points are connected with two opposite sides of the vertex. Because the included angle between two rays is half of the inner angle of a square, it is called a half-angle model, also known as an "angle model with a half-angle".
The conclusion of the half-angle model is that the length of the connecting line between the light and the intersection of the endpoint and the opposite side is equal to the sum of the distances between two adjacent points of the endpoint and its nearest intersection. That is, as shown in the figure, EF=BE+DF.
Application of half-angle model:
Half-angle model is a common model in junior high school geometry problems, which is often used to prove basic geometric propositions and calculate some side lengths and corners. Its inverse theorem makes it more useful and avoids a lengthy proof process.
Refer to the above content: Baidu Encyclopedia-Half Angle Model