A Study on Pre-service Teachers' Discourse about Infinitesimals, Infinite Numbers, and Limits

Abstract

This study investigated seven pre-service teachers’ (who studied analysis) conceptions about infinitesimals, infinite numbers, and explanation methods of limits. Some pre-service teachers thought that infinitesimals and infinite numbers existed. The pre-service teachers who believed that infinitesimals existed explained limits by relying on infinitely small quantities, as did those who believed that infinitesimals did not exist. Some pre-service teachers did not understand the sentences in which quantifiers were used, and they failed to identify statements that contained quantifiers using the Archimedean property of analysis. During interviews, some pre-service teachers demonstrated an intuitive level and did not accept the meta-rules of judging mathematical statements based on axioms and theorems. Their discourse differed from that of analysis in the existence of mathematical objects, endorsed narratives, and meta-rules. This study analyzes the phenomenon of pre-service teachers applying infinitesimals despite having studied standard analysis, focusing on the incommensurability between discourses. This finding can inform teacher education about the curriculum and instruction of analysis.

Keywords

• infinitesimal
• limit
• nonstandard analysis
• quantifier
• discourse
• incommensurability