The Effects of Cabri Geometry for Exploring Geometry in Classroom

Tuyosi Nomura
t-nomura@ma3.justnet.ne.jp
Board of Education in Yuki City Japan
Japan

In order to develop students' logical and mathematical reasoning, geometrical proof has been part of the junior high schools' mathematics curriculum in Japan; but recent research reported that only about twenty percent (20%) of students are able to solve geometrical proof-problems.  The fact that many students could not succeed in writing a proof does not mean that they could not develop logical and mathematical reasoning. For developing their reasoning, the exploration of constructions must be taught a different way. Dynamic Geometry Software, like Cabri Geometry (Cabri) offers a new environment for exploring constructions. This paper discusses the change of reasoning that occurs using Cabri for the learning of geometry. Junior high school students, from twelve to fifteen years old, studied geometry using Cabri. Their change of reasoning is discussed from the following points: exploring the basic constructions in a different way than that of the text book, which could not be observed in the classroom before Cabri; and exploring and understanding the proposition before the proof. It was believed that proof was the only way to understand a proposition in the geometry classroom. But Cabri offers a different way of exploring figures, and also helps students' reasoning from the proposition to the conclusion. Through three years in-class observation, this study points out three major effects of using Cabri: visualizing the character of a figure clearly, a better understanding of the meaning of the theorem, and making clear what the students should be proving.