Objectively speaking, it is a concrete analysis of specific problems. For example, sometimes we use the summation formula of internal angles of triangles, sometimes we use the relationship between internal angles and external angles of triangles, sometimes we use the relationship between parallel lines to get the relationship between congruent angles, internal angles and internal angles on the same side, sometimes we use a circle to get the same angle from the same arc, and the central angle corresponding to the same arc is equal to twice the circumferential angle, and so on! Sometimes the required angle is equal to the known angle by using the congruent similarity of triangles! If your basic skills are solid, it's not a problem to ask for a corner!