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

**Nobuhiko
Nohda**

University of Tsukuba

nobnohda@ningen.hum an.tsukuba.ac.jp

**Abstract**

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.

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