In a relaxed situation, I use the mathematical methods I have learned, such as direct method, reverse deduction method, reduction to absurdity and so on. All available methods, all methods of adding auxiliary lines to experiment. I still didn't give up when there were 15 minutes left. After another five minutes or so, I finally found my own train of thought, not to mention how excited I was at that time. I'm afraid there's not enough time, so I'll get a pen and answer the question quickly. I still have five minutes to answer the question, but when I look at the spelling of my last question, it is much worse than usual. I'm afraid the teacher who corrected the paper can't read it clearly. Fortunately, the final score was 100.