There are four techniques for corner swap: 1. When there are fractions, equations or inequalities about angles in the topic, this formula is generally a relational expression, not a specific value, so it is necessary to consider whether it is suitable for angle and angle exchange;
2. The principle of corner interaction is: simplify the complex and turn the unknown into the known;
3. More often, the sine theorem is used for simplification, especially when there is a homogeneous formula. When there is a formula related to the cosine theorem, such as Example 3 above, the cosine theorem will be used;
4. If the coordinates of the formula are all sides and the cosine value is on the right, the formula on the left is obviously not a cosine theorem, and the cosine value on the right will generally become an angle.