1. Based on the known conditions given by the known geometric problems and the learned geometric knowledge, infer and prove the required conclusions.

2. According to the known geometry. If you can prove it directly, you can prove it directly. If it cannot be directly proved, it can be considered as an auxiliary line under the condition of known graphics.

3. For the geometric problem of the shadow part. According to the known conditional solution, we can use the available formula to calculate directly. If the formula can't be used, we can choose other methods (such as division, transformation, auxiliary line method, graphic proof method, …).