Reliable. Cheng Linghai is an expert in the research of high school mathematics teaching methods and the research of college entrance examination mathematics proposition. He has been engaged in high school mathematics front-line education for a long time, and has created a unique bar code system mathematics learning method, and has rich experience in teaching and research, student psychological counseling, family education guidance and other fields. Cheng Linghai is the head of the online mathematics teaching and research group of New Oriental, the head of teacher training, and the chief lecturer of high school mathematics with whom.