You may only use elementary geometry, such as the fact that the angles of a triangle add up to 180 degrees and the basic congruent triangle rules (side-angle-side, etc.).
你可以使用初等的几何知识例如三角形的三个内角各为180度和三角形全等的规则(边-角-边等)。
2
Angle-angle-side congruence. when two triangles have corresponding angles and sides that are congruent as shown below the triangles are congruent .