1 $ ...$ Write the formula in the middle ... This formula is a part of the text in the text.

2 $$ ...$$ also writes the formula in ... This formula has only one line in the text, but there are no numbers.

3 format is as follows:

\begin{equation}

...

\end{equation}

... is the formula content. This formula is exclusive and has its own number.

The following answer I take the first method as an example, and the three methods can also be replaced.

1 Internal product symbol: $ \ Le Lang \ Central Point, \ Central Point \ wrangell $

The second picture is not clear, mainly subscripts, which can be expressed as follows: A _ {...} {...} The brackets are subscripts and superscripts of A, respectively.

The intersection symbol in the 3 dist function is represented by $ \cap $.

Please note that the above symbols are added to add the following macro package in the introduction area of the document:

\usepackage{amsmath}

\usepackage{amssymb}