Sekao, David2025-05-292025-05-292025-092024-11*S2025http://hdl.handle.net/2263/102581DOI: https://doi.org/10.25403/UPresearchdata.29262554.v1Thesis (PhD (Mathematics Education))--University of Pretoria, 2024.This interpretive qualitative case study aimed to explore teachers’ development of mathematical knowledge for teaching trigonometric functions through Lesson Study. Six participating teachers’ development of mathematical knowledge for teaching trigonometric functions to Grade 11 learners was explored during their collaborative lesson planning, lesson presentation and observation, and post-lesson reflection stages of the South African Lesson Study model. The Mathematical Knowledge for Teaching Framework was used as the lens for the study. Data were collected using observations, document analysis and semi-structured interviews. The study revealed that teachers developed their mathematical knowledge: (1) through collaborative lesson planning discussions (that incorporated all the six knowledge domains) of trigonometric functions content, teaching strategies (or instructional approaches) and learner learning (or thinking), (2) during lesson presentation and observation (that incorporated three knowledge domains) by observing the layout and sequencing of trigonometric functions content and ideas, and the handling of learners’ responses/thinking (oral and written ), (3) through post-lesson reflection conversations (that incorporated all the six knowledge domains) critiquing the achievement of objectives, refining and re-aligning previous and future lessons. The other finding was that teachers reported gaining content and pedagogic skills in trigonometric functions through participating in Lesson Study. Teachers also viewed Lesson Study as an intervention to address poor performance in trigonometric functions. From these findings of my study, I recommend that Lesson Study be adopted as a teacher development model in South Africa’s mathematics education and be used as an intervention to address learners’ problems with trigonometric functions and other problematic topics.en© 2024 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.UCTDSustainable Development Goals (SDGs)Trigonometric functionsLesson StudyMathematical knowledge for teachingKnowledge domainsKnowledge developmentThesisu21833428