It shouldn't be used, and besides, it shouldn't be used. But even if you can use it, try to avoid it. Some problems in geometry may use sine theorem and cosine theorem, but it is better not to use them. For geometric problems without coordinate system, it is best not to build a system. Algebra should not use any theorems, but it is best not to use theorems that do not appear. In short, using theorems or formulas that do not appear in junior high school math books is likely to deduct points, because people I know will be deducted.