It is a feature that you can easily enter mathematical formulas in LaTeX, which is also the origin of LaTeX's last X. You should know that it is silent. Regarding the mathematical formula, I mainly talk about two points: first, the reference of the mathematical formula environment; Another point is the use of the mathematical formula itself. The first thing to say is the environment. The simplest environment is $x$ or, where x can be replaced by any desired expression. A $ is enclosed by an in-line formula and an inter-line formula. They not only have different formula sizes, but also occupy different spaces. To put it simply, $x$ is put in the text, and x$$ will start a new line to write the formula. But these are not enough. If we open our math textbooks, we will find that the representation of symbols in mathematics is almost harsh. Next, I will list some situations that need to use formulas: complete the input of the last three lines. It is convenient to pay attention to the upper subscript in LaTeX. "_" means subscript and ""means superscript. Note that the {enumerate} environment as a whole cannot be placed in a mathematical environment, which is different from other later environments. So it's really a good idea to use {enumerate} when there are words interspersed with labels. If you don't need labels, use {item by item}, which will be used instead of math labels. If you are sure that nothing is needed, you can use \item[] in both {enumerate} and {item} to cancel the digital label of the current line, which is still very neat. Then {eqnarray} can realize the automatic numbering of formulas. Note that the {eqnarray} environment itself is a mathematical environment, so there is no need to add additional symbols such as $. Pay attention to why we should emphasize the mathematical environment, because in the mathematical environment, Chinese can't be input, which is related to the embedding method of CJK, so I won't go into it here. In a word, in the mathematical environment, Chinese can report errors, and English can do the same, but it is best to enclose them with \mathrm{}, otherwise English will be regarded as a variable and the font will be different. Note that in the {eqnarray} environment, press \ \ ENTER, which is consistent with the ordinary text input environment (the functions of the two carriage returns mentioned above are the same as those not mentioned at that time). The usage of&""is very special, similar to the table to be discussed later. When it comes to separators, its function is to keep the formula aligned according to some elements. In essence, it is to divide the content to be displayed into many grids and keep "=" in the grids of the same column, so it is a very simple idea to align according to "=".