The teaching order of the five compulsory modules is not clearly stipulated in the Mathematics Curriculum Standard for Ordinary Senior High Schools (Experiment). According to the actual situation of schools in various provinces and regions, there are generally three different module sequences (12345, 12453, 14523). If you have finished the required course and studied the required course 4 repeatedly, you can be sure that you should study the required textbook in the order of 14523. The selection order of some textbooks is completely decided by each school, and many are decided by teachers themselves. There is no uniform requirement in schools.