Mainly read more books, understand the solutions and principles of various models, and then apply these principles for simple derivation and calculation, and do some problems appropriately.

It looks difficult and scary, but if you really look carefully, you will find that it is not difficult.

The formulation of mathematical physics is very important for the study of subsequent courses.

Reference books, you can refer to the mathematical and physical equations edited by Xie, and the mathematical and physical equations of some books called mathematical and physical methods.