Duiseke A.2026-03-122026-03-122025Duiseke A / Methodology of solving complex problems associated with an isosceles triangle / SDU University / Department of Pedagogy of Natural Scienceshttps://repository.sdu.edu.kz/handle/123456789/2520This study examines the impact of solving complex problems related to isosceles triangles on the development of students' geometric thinking and academic achievements. The research project included a performance test and an attitude test. The study was conducted with 24 students of the seventh grade, who were divided into two groups: experimental and control. The performance test, which included a pre-test and a follow-up test, measured the students' performance before and after the intervention. In the control group, students received traditional instruction, while the experimental group studied problem-based learning (inquiry-based learning). Analysis of the results of the test on academic achievement showed that students in the experimental group demonstrated significantly higher performance in mathematics compared to the control group. This demonstrates the effectiveness of the IBL methodology in improving learning outcomes. A survey was used to assess attitudes towards mathematics. Analysis of the survey showed a significant improvement in attitude to the subject after the intervention. The results showed a significant improvement in students' ability to solve geometric problems in the experimental group. Conclusions emphasize the effectiveness of structured problem solving and conceptual understanding in improving logical reasoning and academic outcomes.enisosceles trianglegeometric thinkingcomplex tasksArticle