thickness method: the first step in reading is "from thin to thick". That is to say, reading should be down-to-earth, and every concept and theorem should be thorough and clear. In this way, a thin book has become "thicker" because of a lot of content, which is "from thin to thick" After this step, there is a more important step, that is, on the basis of the first step, we can analyze and summarize, grasp the essence, grasp the whole, and achieve mastery. After such careful analysis, you will feel that there are not many things that should be remembered. This is a process of "from thick to thin" to really improve efficiency.