Análise dos tipos de provas matemáticas e pensamento geométrico de alunos do 1º ano do Ensino Médio

Abstract

The present research work investigated the level of geometric thinking and the types of mathematical proofs by 1st year high school students from the application of a Didactic Proposal. This research was constituted as a qualitative one, and as case study, having instruments of the application an essay with the theme Proofs and Mathematical Demonstrations, Didactic Proposal developed by a team of five members who worked collaboratively, inserted in the Project CAPES/OBEDUC/UFMS/UEPB/UFAL Edital 2012, participant observation and audio recording. We developed the didactic proposal with 18 activities, divided into four parts, which stimulated students to reflect, justify, prove and demonstrate. The application of this proposal occurred in June 2015 for 1st year high school students in a public school in the city of Areia, Paraíba. Our research took place in three moments. In the first moment, we apply the essay on the subject mathematical proofs and demonstrations. In the second moment we did a didactic intervention approaching definitions, theorems, proofs and mathematical demonstrations with the objective of taking to the students this knowledge. In the third moment, Part I and II of the Didactic Proposal were applied, involving activities to conjecture and demonstrate the Pythagorean Theorem, Internal Angle Sum Theorem and External Angle Theorem. This proposal helped in the investigation of the mathematical knowledge of the 1st year high school students, divided into 8 pairs and one trio, chosen freely. The two pairs of students who achieved the best performance in our Didactic Proposal were chosen for our case study and the one of better performance had its dialogue recorded and transcribed as a source of evidence of our case study. In our research we analyzed the answers given by the two pairs on Activities 1 and 3 (Part II) and Activity 2 (Part III), totaling in 3 questions. We used the data triangulation method for our case study. Firstly, we draw the profile of the two pairs of students in relation to Proofs and Mathematical Demonstrations. Next, we investigate the types of mathematical proofs used by them and their geometric thinking. To do so, we use discussions about the levels of geometric thinking proposed by Van Hiele and the types of evidence. From our results we can conclude that the pairs of students were able to develop informal justifications, that is, informal proofs. Thus, the pairs presented pragmatic evidence and the types of evidence Pragmatic Justification and Crucial Example. Regarding the geometric thinking proposed by Van Hiele, only one pair could be classified in one of the levels of development of geometric thinking, Level 3, informal deduction. Therefore, we come to the end of this research convinced that it is necessary to start working mathematical proofs and demonstrations in the basic education level, adapting its teaching to the degree of maturity and to the mathematical knowledge of the students, since our results point out that this subject is not approached properly in the classroom.