A Study on the Investigation of Students' Reasoning Skills in Secondary Geometry Proofing

Geometry reasoning is an ability that helps students build their thinking skills in logic structures, deductive reasoning,analytical reasoning, and problem-solving. Geometric proof is a key indicator to develop those skills. However, writing proofs ischallenging for students, especially those unwilling to work hard. This case study used a mixed method to explore Year 10 students'geometry reasoning abilities in proving geometric questions and aims to find effective strategies for teaching proof. Data werecollected through tests, demonstrated in percentages, and van Hiele’s model rubric was applied to analyse students' geometryreasoning levels. Four examples representing different reasoning levels were examined, discussed and combined with theinterviewed data from the 10 participants, strategies that targeted students' needs were summarised for future planning and teaching.Qualitative data were categorised and themed to provide details for teaching and learning. The study’s results showed that about88 % of students belonged to levels III and IV, while, about 12% of students, whose level belonged to Levels I and II needed supportin writing proof. The results of this study suggest that effective teaching methods and strategies are required to support students’geometry reasoning abilities.