Development of Geogebra-Assisted Learning Materials for Circle Topics Based on the van Hiele Model

This study aims to develop GeoGebra-assisted instructional materials on circle topics based on the van Hiele model that meet the criteria of validity, practicality, and effectiveness. The study employed a Research and Development (R&D) approach using the 4D model, consisting of the Define, Design, Develop, and Disseminate stages. The participants were high school students divided into an experimental group and a control group. Data were collected through validation sheets, observation sheets, student response questionnaires, readability tests, and learning outcome assessments. The results indicate that the developed materials are valid, with average validity scores ranging from 3.58 to 3.85. Practicality was demonstrated by a high level of instructional implementation (3.75), very high student activity (93.2%), and highly positive student responses (92.68%). Effectiveness was confirmed by a classical mastery rate of 89%, a high N-Gain score (0.77), and a statistically significant difference between the experimental and control groups (p < 0.05). These findings suggest that GeoGebra-assisted instructional materials based on the van Hiele model are effective in improving students’ mathematics learning outcomes, particularly in geometry.