In the process of solving problems, it is sometimes necessary to add auxiliary lines. In the senior high school entrance examination in Chengdu, only one simple proof question does not need to be added with auxiliary lines, and the rest involve adding auxiliary lines. The requirements for students to add lines in the senior high school entrance examination are quite high, but almost all of them follow the principle of constructing graphs required by theorems or construct some common basic graphs.

Breakthrough 2: can't do it, find similarity, have similarity, and use similarity.

The finale involves many knowledge points and it is difficult to transform knowledge. Students often don't know how to start, and they should always look for similar triangles according to the meaning of the question.

Breakthrough point 3: stick to the invariants and be good at using the methods or conclusions adopted in the previous questions.

When the movement of the figure changes, the position, size and direction of the figure may change, but in this process, there are often some two line segments, or some two angles, or some two triangles corresponding to the position or quantitative relationship does not change.

Point 4: Find the information of multiple solutions in the topic.

There are more than one situation in which a graph may meet the conditions in motion, that is, two solutions or multiple solutions. How to avoid missing answers is also a headache for candidates. The information of multiple solutions can actually be found in the topic, which requires us to dig deep into the topic, in fact, it is repeated and serious examination.