1, SSS method: If three sides of two triangles are equal, then the two triangles are congruent triangles.
2.SAS method: If two sides of two triangles and the included angle between them are equal, then the two triangles are congruent triangles.
3.ASA method: If one angle and two sides of two triangles are equal to the corresponding angles and opposite sides of another triangle, then these two triangles are congruent triangles.
4.RHS method: If the hypotenuse of two right-angled triangles and a right-angled side are equal, the two triangles are congruent.
5.SAA method: If two triangles have two equal internal angles and one side is equal, then the two triangles are congruent triangles.
Among the congruence judgment methods, SSS method, SAS method and ASA method are necessary and sufficient conditions. RHS method and SAA method are only sufficient conditions. When judging, you need to compare all the conditions. If one or more of these conditions are met, it can be concluded that these two triangles are congruent.
The use of triangles
Triangle is the most basic figure in geometry, and their properties and theorems have laid a solid foundation for geometry. In the design and construction of buildings, triangles, as a stable structure, are used to build various types of buildings, bridges and roads. The nature of triangle makes it a common tool for measurement and navigation. Mathematically, the properties and theorems of triangles are widely used in mathematical analysis, physics and other fields. In art, the shape of a triangle is also often used to compose pictures and express emotions.