A comparative analysis of congruent triangle units in textbooks from China and the United States

In this article, we report findings from a comparative study of the introduction and development of triangle congruence in two textbooks: a high school geometry textbook from the United States and an eighth-grade mathematics textbook from China. Using the mathematics curriculum as a story (MCS) framework developed by Dietiker and additional coding schemes, we illustrate how each textbook designs its congruent triangle lessons with the goal to provide students a fertile ground for the development of geometry reasoning and proof. Through the analysis of the characters, actions, settings, and plots of each story, we identify both similarities and differences. Both textbooks introduced the same sets of side–angle criteria that proved the existence of the unique triangle as well as that did not support a unique triangle. Yet, the U.S. textbooks introduced side–angle–side first while the Chinese textbooks started with side–side–side. In addition, the findings demonstrate the illuminating power of the MCS framework to fill the gap of current textbook analysis research.