J. Mendoza1, R.C. Pati1, J. Villena1, C.J. Aduana1, L. Elipane2

1De La Salle University (PHILIPPINES)
2De La Salle University and Philippine Normal University (PHILIPPINES)
Teaching students on how to write proofs is a daunting task for the teachers as it requires good reasoning skills among students. Several studies in the Philippines have shown that the students' reasoning skills does not match the level of skill required for them to write geometric proofs. A change in the teaching practices such as exposing the students to manipulative tasks is suggested as it constantly improves their thinking skills and results to a better understanding of mathematics concepts and principles.

This paper reports on a lesson study that explored the use of GeoGebra, a dynamic geometry software, as an alternative way to teach the Inscribed Angle Theorem and its proof. Lesson Study (LS) is a professional development approach focused on improving the teaching-learning process on a particular lesson where teachers work collaboratively. LS involves planning, formulating the design of the lesson, teachers’ observation, and post-lesson conference where the observers share their insights about the lesson.

Using the ‘Plan, Do, See’ Cycle, the results showed that:
(1) using and maximizing a dynamic geometry software such as GeoGebra can assist the students in constructing figures, recognizing patterns, and creating generalizations in a shorter period of time, which then leads them in attaining more meaning and deeper understanding of the lesson; and
(2) the positive effects of a teaching-learning intervention could only be maximized if the students’ skills match the skills required for a learning competency.