Geometrical proof processes and tendencies of 8th grade students

The aim of this study is to investigate 8th grade students? geometrical proof and reasoning processes and their tendencies to proof representations in terms of deductive and inductive reasoning. The present study is considered to be helpful to determine the needs of our country with respect to mathematical proof instruction, to determine the strategies to be followed for improving the students? geometrical proving processes, to determine the role of the teacher in proving process, and to shed a light to classroom activities according to the determined strategies.The study was carried out with 154 students in two primary schools in Bursa. Eight open-ended questions related to 6th and 7th grade geometry subjects where triangle and angles were given importance were prepared by the investigator.In geometry, Proof, starting from Euclid, has been carried out in other fields up to date. In this context, the sources of Bell (1976), (Stylianides 2007) have been the main sources which shed a light to our studies.For the analysis of the data, percentage and frequency tables were used. When analyzing the data, three aspects of mathematical proof (justification, explanation, and systematizing) suggested by Bell were used. Additionally, when determining sub-problems, two properties of in-classroom proofs (proving procedures and proof representation types) set forth by Stylianides in 2007 were taken into consideration.The results indicated that the situation of inferring a new truth from generally known truths was rarely encountered, while reaching the truth indirectly (method of reductio ad absurdum, proof by contradiction) was almost non-existing. The results also indicated that although the students were able to justify a valid statement, they were not able to refute an invalid statement (opposite example, contradiction). The findings showed that the most preferred proof type was numerical sampling and visual proof whereas the least preferred one was algebraic proof.