ABSTRACT Recognising teachers’ knowledge as one of the main factors influencing their practices and student learning, we aim to contribute to obtaining a better and deeper understanding of the specificities of teachers’ mathematical knowledge. A case study involving one 8th-grade Chilean mathematics teacher is presented in the context of rational numbers. Using video and audio recordings of classroom practices, questionnaires, and an interview, we sought to characterise, and better understand the content of the Knowledge of Topics from the perspective of the Mathematics Teachers’ Specialized Knowledge (MTSK) theoretical framework. The results reveal some critical aspects that teacher education should focus on, while also identifying lost opportunities and examples of “good” practices, thus contributing to the refinement of the MTSK conceptualisation. The conclusions can be considered in a broader perspective, with implications for teacher education in other contexts.

中文翻译：

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数学教师专业知识：中学教师的有理数知识

摘要 认识到教师的知识是影响他们的实践和学生学习的主要因素之一，我们的目标是有助于更好、更深入地了解教师数学知识的特殊性。在有理数的背景下介绍了一个涉及一位 8 年级智利数学教师的案例研究。通过课堂实践、问卷调查和访谈的视频和录音，我们试图从数学教师专业知识（MTSK）理论框架的角度表征和更好地理解主题知识的内容。结果揭示了教师教育应该关注的一些关键方面，同时还确定了失去的机会和“良好”做法的例子，从而有助于完善 MTSK 概念化。可以从更广泛的角度考虑这些结论，对其他背景下的教师教育也有影响。