<![CDATA[Preliminary observations and interviews with teachers identified low levels of students’ mathematical representation skills in junior high school mathematics learning, particularly in representing mathematical concepts in visual, symbolic, and verbal forms. The limited use of technology-based teaching materials also highlights the need for learning resources that integrate an appropriate instructional model with interactive technology. This study aimed to develop an APOS (Action, Process, Object, and Schema) model Student Worksheet assisted by GeoGebra for the topic of Lines and Angles and to examine its validity, practicality, and effectiveness. This Research and Development study employed the ADDIE model, comprising Analysis, Design, Development, Implementation, and Evaluation stages. The research subjects were 30 seventh-grade students at SMP Negeri 28 Bengkulu Selatan, with 10 selected through purposive sampling for a small-group practicality trial. Data were collected using expert validation sheets, student response questionnaires, and pretest and posttest instruments. The results showed an Aiken’s V coefficient of 0.86, indicating a high level of validity; a practicality score of 83.7%, categorized as practical; and an N-Gain score of 0.60, indicating a moderate improvement in students’ mathematical representation skills. The developed Student Worksheet integrates APOS-based concept construction with dynamic GeoGebra visualization, thereby providing a technology-based learning resource for the topic of Lines and Angles.]]>
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