The intention of this article is to consider the use of narrative and rhetorical inquiry as research methods. I construct a mathematical biography of one elementary teacher trainee, Sirpa, who had performed well in her advanced mathematics course in upper secondary school. I describe her development as a mathematics teacher during teacher education from her second-year methods course and teaching practice to fourth-year teaching practice. Narrative inquiry is more than a case study: Sirpa's mathematical biography is a story that describes how she constructs her mathematical identity. I also analysed the key rhetoric that Sirpa used in her talk, key rhetoric here referring to the strategy by which she constructed continuity and coherence.