The subject wants to ask "which version of mathematics is used in senior one in Dongcheng District"? Beijing normal university edition. According to the inquiry of Dongcheng District Education official website, the mathematics textbook for junior high schools in Dongcheng District is a version published by Beijing Normal University, accounting for 95% of junior high schools in Beijing and 98% of the total number of junior high school students, which is a widely used version. Dongcheng District, belonging to Beijing, is located in the east of downtown Beijing.