There is a set of formulas. It should be in the reference book. It slipped my mind. They are all in college now.

This formula can list many relationships, I think it is 6~7, and almost many relationships between points can be deduced.

First, carefully understand the relationship between the line points, and then formulate the formula. Don't think about how to solve it, just list their relationships first, and then choose useful relationships through each relationship before solving it. Don't bring numbers first, use letters to express them, so that you can better understand the relationship.